. 


WELLS'S 


PKINCIPLES  AND  APPLICATIONS 


OP 


CHEMISTRY; 


FOB  THE 


USE  OF  ACADEMIES,  HIGH-SCHOOLS,  AND  COLLEGES: 


LATEST  RESULTS  OP  SCIENTIFIC  DISCOVERT  AND   RESEARCH,   AND 
ARRANGED  WITH  SPECIAL   REFERENCE  TO  THE  PRACTICAL     - 
APPLICATION   OF  CHEMISTRY  TO  THE  ARTS  AND 
EMPLOYMENTS  OF   COMMON  LIFE. 


WITH  TWO  HUNDRED  AND  FORTY  ILLUSTRATIONS, 


BY 

DAVID   A.   WELLS,   A.M., 

ATTTHOB  OF   "  WELLS'8  NATURAL  PH^I^SOPHY,"    '.'  SCIENCE  0V  COMMON  THINGS," 
EDITOB  OF  THE   "ANNvTAC  <JT>  4c^BNTtFIO  DIBCOyMay'"    BTO. 


NEW    YOKK: 
IVISON   &   PHINNEY,  321   BROADWAY. 

CHICAGO :  S.  C.  GRIGGS  &  CO.,  39  &  41  LAKE  ST. 

CINCINNATI  :     MOORE,    WIL8TACH,    KEYS   &   CO.      ST.    LOUIS  '.    KEITH    le    WOODS.  ' 
PHILADELPHIA  I   SOWER,  BARNES  &  CO.     BUFFALO  :   PHINNEY    k   CO. 

NBWBUBG:  T.  s.  QUACKENBUSH. 
1858T 


Entered,  according  to  Act  of  Congress,  in  the  year  1858,  by 

I  VI SON    &    PHINNEY, 
In  the  Clerk's  Office  of  the  District  Court  for  the  Southern  District  of  New  York. 


BT 

T.   B    SMITH  &  SON, 
82  &  84  Beokman-street,  N.  Y. 


PRINTED    BT 

J    D.  BEDFORD   &  CO. 
115  &  11T  Franklin-street. 


PREFACE. 


THIS  work  lias  been  prepared  with  special  reference  to 
the  wants  of  students  in  Academies,  Seminaries,  and  Col- 
leges, aiming  to  furnish  just  that  information  which  will 
prove  most  useful  and  practical  in  their  future  employ- 
ments and  relations  of  life. 

The  great  general  principles  of  Chemistry,  and  the 
more  important  of  the  elements  and  their  compounds,  have 
been  accordingly  very  fully  discussed  ;  while,  on  the  other 
hand,  the  custom  adopted  in  many  text-books  of  enumer- 
ating and  describing  compounds  which  have  no  practical 
value  and  little  scientific  interest,  has  been  disregarded. 

To  enable  the  student  to  understand  more  clearly  the 
relations  which  Chemistry  sustains  to  'the  industrial  ope- 
rations of  the  age,  and  to  the  past  and  present  progress 
of  civilization,  greater  attention  has  been  given  to  the  his- 
tory of  the  science  than  has  heretofore  been  customary  in 
elementary  text-books. 

Special  care  has  also  been  taken  to  present  the  very  latest 
results  of  scientific  discovery  and  research,  in  this  country 
and  Europe,  and  to  take  advantage  of  the  most  approved 
methods  of  experimentation  and  instruction. 

An  unusually  large  number  of  illustrations  has  been 
introduced,  with  the  double  purpose  of  rendering  the 
study  of  the  science  more  intelligible  and  attractive  to 
the  pupil,  and  of  facilitating  the  instructions  of  teachers, 

258234 


IV  PREFACE, 

especially  of  those  not  enjoying  the  advantage  of  large  ap- 
paratus. 

In  respect  to  originality  the  author  makes  little  pre- 
tension beyond  the  arrangement  and  classification  of  sub- 
jects, and  the  selection  of  illustrations.  Among  the 
authorities  to  which  he  is  especially  indebted  he  would 
mention  FARADAY,  Prof.  MILLER,  of  King's  College,  Lon- 
don, GRAHAM,  KEGNAULT,  and  HAYES. 


NEW  YORK,  May,  1858. 


CONTENTS. 


•SMP 
INTRODUCTION... 9 


CHAPTER   I. 

ON  THE  CONNECTION  OP  GRAVITY,  COHESION,  ADHESION,  AND  CAPILLARY 

ATTRACTION  WITH  CHEMICAL  ACTION 22 

SECTION  I. — GRAVITY, 22 

"       IL — COHESION 29 

"     III. — ADHESION  AND  CAPILLARY  ATTRACTION. 32 

11      IV. — CRYSTALLIZATION. 44 


CHAPTER    II. 

HEAT 56 

SECTION  I. — SOURCES  OF  HEAT 60 

"       II. — COMMUNICATION  OF  HEAT 63 

"     HI.— EFFECTS  OF  HEAT...  ...  75 


CHAPTER    III. 

LIGHT 112 

SECTION  L — NATURE  AND  SOURCES  OF  LIGHT 112 

.  "      IL — PROPERTIES  OF  LIGHT..,  115 


CHAPTER    IV. 
ELECTRICITY. 130 


VI  CONTENTS. 

INORGANIC    CHEMISTRY. 

CHAPTER    V. 

GENERAL  PRINCIPLES  OF  CHEMICAL  PHILOSOPHY 156 

CHAPTER,    VI. 

THE  NON-METALLIC  ELEMENTS 184 

SECTION  I. — OXYGEN 184 

"      II. — MANAGEMENT  or  G-ASES 196 

"     III. — HYDROGEN. 199 

"•       IV. — NlTRO€SENr  OR  AZOTE 219) 

•*       V. — CHLORINE 235 

"•     VI. — IODINE 253 

"    VII— BROMINE 255 

"  VIII. — FLUORINE 256 

"      IX.— SULPHUR 258 

"        X. — SELENIFM  AND  TELLURIUM 268 

u     XL— PHOSPHORUS 269 

"    XIL— BORON 276 

"  Xin.— SILICON,  OR  SILICIUM 279 

"  XIV.— CARBON 282 

CHAPTER    VII. 
COMBUSTION. 30t 

CHAPTER    VIII. 
THE  METALLIC  ELEMENTS 324 

CHAPTER    IX. 

THE  METALS  OF  THE  ALKALIES. 32T 

SECTION  I. — POTASSIUM. 32T 

«      IL— SODIUM. 333 

u     III— LITHIUM 339 

"      IV.— AMMONIUM 339 

CHAPTER    X. 

METALS  OF  THE  ALKALINE  EARTHS 343 

SECTION  L — BARIUM  AND  STRONTIUM 343 


CONTENTS.  Vll 

PAGE 

SECTION  II. — CALCIUM 344 

"      III. — MAGNESIUM 349 


CHAPTER    XI. 

METALS  OF  THE  EARTHS 350 

SECTION  I. — ALUMINUM...  .  351 


CHAPTERXII. 
GLASS  AND  POTTERY 355 

CHAPTER    XIII. 

THE  COMMON,  on  HEAVY  METALS * 360 

SECTION  I. — IRON 360 

"       II. — MANGANESE  AND  CHROMIUM 367 

"     HI. — COBALT  AND  NICKEL 370 

"      IV.— ZINC  AND  CADMIUM 871 

"       V. — LEAD'  AND  TIN 372 

"     VI— COPPER  AND  BISMUTH. 377 

"   VII. — URANIUM,  VANADIUM,  TUNGSTEN,  COLUMBIUM,  TITA- 
NIUM, MOLYBDENUM,  NIOBIUM,  PELOPIUM,  ILMENIUM, 

ETC 380 

if  Yin.— ANTIMONY  AND  ARSENIC 380 

CHAPTER    XIY. 

THE  NOBLE  METALS 385 

SECTION  I. — MERCURY 385 

"      .II.— SILYER. 388 

"     III.— GOLD 392 

"     IV. — PLATINUM,  PALLADIUM,  EHODIUM,  RUTHENIUM,  OS- 
MIUM, IRIDIUM 395 

CHAPTER^  XV. 
PHOTOGRAPHY 397 


Viii  CONTENTS. 

ORGANIC    CHEMISTRY. 

CHAPTER    XVI. 

PAGE 

NATURE  OP  ORGANIC  BODIES 401 

CHAPTER    XVII. 

ESSENTIAL  IMMEDIATE  PRINCIPLES  OP  PLANTS 405 

SECTION  I. — VEGETABLE  TISSUE,  STARCH,  GUM,  SUGAR. 405 

"      H.— ALBUMEN,  CASEINE,  GLUTEN 421 

CHAPTER    XVIII. 

NATURAL  DECOMPOSITION  OP  ORGANIC  COMPOUNDS 424 

CHAPTER    XIX. 
ALCOHOL  AND  ITS  DERIVATIVES 433 

CHAPTER    XX. 
VEGETABLE  ACIDS 450 

CHAPTER    XXI. 
ORGANIC  ALKALIES 455 

CHAPTER    XXII. 
ORGANIC  COLORING  PRINCIPLES 45? 

CHAPTER    XXIII. 
OILS,  FATS,  AND  RESINS 461 

CHAPTER    XXIV. 

THE  NUTRITION  AND  GROWTH  OP  PLANTS. 475 

CHAPTER    XXV. 

ANIMAL  ORGANIZATION  AND  PRODUCTS 482 

APPENDIX..  502 


PRINCIPLES  OF  CHEMISTRY, 


INTRODUCTION. 

1.  Matter  is  the  general  name  which  has  been  given 
to  that   substance  which,  under  an  infinite  variety  of 
forms,  affects  our  senses.     We  apply  the  term  matter  to 
every  thing   that   occupies   space,    or  that  has  length, 
breadth,  and  thickness. 

The  forms  and  combinations  of  matter  seen  in  the  animal,  vegetable,  and 
mineral  kingdoms  of  nature,  are  numberless,  yet  they  are  all  composed  of  a 
very  few  simple  substances  or  elements. 

2.  Simple  Substances, — By  a  simple  substance,  or  ele- 
ment, we  mean  one  which  has  never  been  derived  from, 
or  separated  into,  any  other  kind  of  matter. 

Sulphur,  gold,  silver,  iron,  oxygen,  and  hydrogen,  are 
examples  of  simple  substances  or  elements  ;  and  are  so 
considered  because  we  are  unable  to  decompose  them, 
convert  them  into,  or  create  them  from,  other  bodies. 

No  known  force  has  yet  extracted  any  thing  from  sulphur  but  sulphur,  or 
from  gold  but  gold  ;  but  if  by  any  method  these  substances  could  be  broken 
up  into  two  or  more  factors,  or  component  parts,  they  would  cease  to  be  re- 
garded as  elementary. 

The  number  of  the  elements,  or  simple  substances,  with 
which  we  are  at  present  acquainted,  is  sixty-two. 

These  substances  are  not  all  equally  distributed  over 
the  surface  of  the  earth  :  many  of  them  are  exceedingly 
rare,  and  known  only  to  chemists.  Of  the  whole  number, 
from  ten  to  fifteen  only  are  concerned  in  the  formation  of 

QUESTIONS. — What  is  matter  ?  What  is  a  simple  substance,  or  element  ?  What  is  the 
number  of  the  elements  ?  How  are  the  elements  distributed  ? 

1* 


10  PRINCIPLES     OF     CHEMISTRY. 

the  great.'balk  of  .all  -the  .-familiar  objects  we  see  around 
us. 

The  atfmcs^htEfce  is  srado  u|»  of.  two— oxygen  and  nitrogen — with,  compar- 
atively speaking,  'faem  tracjes  of  carbon  and  hydrogen:  two  of  these,  again — 
oxygen  and  hydrogen — give  rise  to  -water,  a  substance  covering  three  fourths 
of  the  surface  of  OUT  planet;  while  the  great  rock  masses  of  the  earthr  are 
mainly  compounds  of  eight  simple  substances,  viz.,  oxygen,  silicon,  alumin- 
ium, calcium,  potassium,  sodium,  chlorine,  and  iron.  In  the  composition 
also  of  animal  or  vegetable  structures,  the  same,  or  a  still  greater  simplicity 
is  observed. 

3.  Componnd  Bodies. — A  Componnd  Body  is  one  that 
can  be  separated  into-  two  or  more  elements,  or  simple 
substances. 

4.  Atoms. — All  matter  is  supposed  to  be  composed  of 
exceedingly  minute  particles,  which  can  not  be  subdi- 
vided, or  separated  into  parts.     Such  ultimate  particles 
are  termed  ATOMS. 

No  one  has  ever  seen  an  atom  ;  no  one  has  ever  been  able  to  recognize 
through  the  agency  of  the  senses  a  portion  of  matter  so  small  that  it  could 
not  in  some  way  be  made  smaller;  yet  the  evidence  on  this-  subject,  derived 
mainly  from  modem  investigations  in  chemistry,  is  of  such  a  character  that 
there  can  be  no  reasonable  doubt  that  all  matter  is  ultimately  composed  of 
indivisible  parts,  or  atoms.  The  natvure  of  this  evidence  wfll  be  mentioned 
hereafter. 

Simple,  or  elementary  bodies,  have  simple  atoms,  and 
eompoand  bodies  compound  atoms.  The  atoms  of  each 
substance  undoubtedly  differ  in  weight,  and  may  possibly 
differ  in  size  and  form. 

Mare-cules, — We  use  the  term  MOLECULE,  or  PARTICLE 
of  matter,  to  designate  very  small  quantities  of  a  substance, 
not  meaning,  however,  the  ultimate  atoms.  A  molecule, 
or  partiele  of  matter,  may  be  supposed  to  be  formed  of 
several  atoms  united  together. 

The  extent  to  which  matter  can  be  divided,  and  perceived  by  the  senses,  is 
most  wonderful.  A  grain  of  musk  will  fill  the  air  of  a  room  for  years  with 
fragrant  particles,  without  suffering  any  considerable  loss  of  weight.  In  the 
manufacture  of  gilt  wire,  used  lor  embroidery,  the  amount  of  gold  employed 
to  cover  a  foot  of  wire  does  not  exceed  the  720,000th  part  of  an  ounce. 

QUESTIONS.— What  is  a  Compound  Body?  What  is  supposed  to  be  the  ultimate  con- 
stitution of  matter?  What  are  atoms?  What  is  a  molecule .?  Illustrate  tha  divisibility 
of  matter. 


INTRODUCTION.  11 

The  manufacturers  know  this  to  be  a  fact,  and  regulate  the  price  of  their  wire 
accordingly.  But  if  the  gold  which  covers  one  foot  is  the  720,000th  part  of 
an  ounce,  the  gold  on  an  inch  of  the  same  wire  will  be  only  the  8,640,000th 
part  of  an  ounce,  We  may  divide  this  inch  into  one  hundred  pieces,  and  yet  seo 
each  piece  distinctly  without  the  aid  of  a  microscope ;  in  other  words,  we  seo 
the  864,000,000th  part  of  an  ounce,  If  we  now  use  a  microscope,  magnifying 
five  hundred  times,  we  may  clearly  distinguish  the  432,000,000,000th  part  of 
an  ounce  of  gold,  each  of  which  parts  will  be  found  to  have  all  the  characters 
and  qualities  which  are  found  in  the  largest  masses  of  gold. 

Some  years  since,  a  distinguished  English  chemist  made  a  series  of  experi- 
ments to  determine  how  small  a  quantity  of  matter  could  be  rendered  vis- 
ible to  the  eye,  and  by  selecting  a  peculiar  chemical  compound,  small  portions 
of  which  were  easily  discernible,  he  came  to  the  conclusion  that  he  could  dis- 
tinctly see  the  billionth  part  of  a  grain.  This  quantity  may  be  represented  in 
figures  thus,  1,000,000,000,000,  but  the  mind  can  form  no  rational  conception 
of  it. 

5.  Porosity, — No  two  atoms  of  matter  are  supposed  to 
touch,  or  be  in  actual  contact  with  each  other,  and  the 
openings  or  spaces  which  exist  between  them  are  called 
PORES.     This  property  of  bodies,  according  to  which  their 
atoms  are  thus  separated  by  vacant  places,  is  called  PO- 
ROSITY. 

The  reasons  for  believing  that  the  atoms  or  particles  of 
matter  do  not  actually  touch  each  other,  are,  that  every 
form  of  matter,  so  far  as  we  are  acquainted  with  it,  can,  by 
pressure,  be  made  to  occupy  a  smaller  space  than  it  origin- 
ally filled.  Therefore,  as  no  two  particles  of  matter  can 
occupy  the  same  space  at  the  same  time,  the  space,  by 
which  the  size  or  volume  of  a  body  may  be  diminished  by 
pressure,  must,  before  such  diminution  took  place,  have 
been  filled  with  openings,  or  pores,  Again,  all  bodies  ex- 
pand or  contract  under  the  influence  of  heat  and  cold. 
Now,  if  the  atoms  were  in  absolute  contact  with  each 
other,  no  such  movements  could  take  place. 

The  porosity  of  liquids  may  be  proved  by  mixing  together  equal  measures 
of  strong  alcohol  and  water ;  when  the  resulting  compound  will  be  found  to  oc- 
cupy considerably  less  space  than  its  two  constituents  did  separately : — in  other 
words,  a  gallon  of  each  liquid  mixed  will  not  form  two  gallons  of  compound. 

6.  Inertia,— Matter  of  itself  has  no  power  to  change  its 

QTJESTIONS.— What  are  pores  ?  Ate  the  particles  of  matter  in  absolute  Contact  ?  How- 
may  the  porosity  of  liquids  be  shown  ?  Has  matter  any  power  in  itself  to  change  its  con- 
dition? 


12  PRINCIPLES    OF    CHEMISTRY. 

state,  or  form.  If  a  body  is  at  rest,  it  can  not  of  itself 
commence  moving ;  and  if  a  body  be  in  motion,  it  can 
not  of  itself  stop,  or  come  to  rest.  Motion,  or  cessation 
of  motion  in  a  body,  or  any  other  change  of  its  condition, 
requires  a  power  to  exist  independent  of  itself. 

As  the  cause  of  all  the  changes  observed  to  take  place 
in  the  material  world,  we  admit  the  existence  of  certain 
forces,  or  agents,  which  govern  and  control  all  matter. 

7.  Force  is  whatever  produces   or  opposes  motion  or 
change  in  matter. 

Causes  of  Change,— All  the  changes  which  we  observe  to 
take  place  in  matter  may  be  referred  to  the  following  causes, 
or  forces  : — The  ATTRACTION  OF  GRAVITATION,  MOLECU- 
LAR FORCES — or  forces  acting  only  between  molecules,  or 
particles  of  matter  at  insensible  distances — FORCES  devel- 
oped through  the  agencies  of  LIGHT  and  HEAT,  the  AT- 
TRACTIVE and  KEPULSIVE  FORCES  of  ELECTRICITY  and 
MAGNETISM — and  finally,  a  force  or  power  which  exists  only 
in  living  animals  and  plants,  which  is  called  VITAL  FORCE. 

Concerning  the  real  nature  of  these  forces,  we  are  entirely  ignorant.  We 
suppose,  or  say,  they  exist,  because  we  see  their  effects  upon  matter.  In  the 
present  state  of  science,  it  is  impossible  to  know  whether  they  are  merely 
properties  of  matter,  or  whether  they  are  forms  of  matter  itself,  existing  in 
an  exceedingly  minute,  subtile  condition,  without  weight,  and  diffused 
throughout  the  whole  universe.  The  general  opinion,  however,  among  scien- 
tific men,  at  the  present  day,  is,  that  these  forces,  or  agents,  are  not  matter, 
but  properties,  or  qualities,  of  matter. 

8.  Gr  a  vital  ion, -The  Force  of  Gravitation,  or  the  At- 
traction of  Gravitation,  is  the  name  applied  to  that  force  by 
which  all  the  bodies  in  the  universe  at  sensible  distances 
attract  and  tend  to  approach  each  other.     Gravitation  dif- 
fers from  all  other  forces  in  the  fact  that  its  influence  is 
universal ;  that  it  acts  at  all  times,  upon  all  matter,  and 
at  all  distances. 

The  force  of  gravitation  belongs  equally  to  the  smallest  atom  and  to  the 
largest  world,  producing  those  attractions  which  bind  masses  of  matter  to- 

QTJESTIONB.— What  occasions  change  in  matter  ?  What  is  force  ?  Enumerate  the  great 
forces  of  nature.  What  do  we  know  concerning  these  forces  ?  What  is  gravitation  ?  Is 
the  for^p  of  gravitation  universal  ? 


INTRODUCTION.  13 

gether,  and  restrict  the  motions  of  the  planets  to  regular  orbits.    It  is  the 
force  which  draws  a  small  body,  free  to  move,  toward  a  larger. 

Terrestrial  Gravitation  is  that  force  by  which  all  bodies 
upon  the  earth  are  attracted  toward  its  center. 

The  measure  of  this  force,  or  the  strength  with  which 
a  body  upon  the  earth  is  attracted  toward  its  center,  is 
called  Weight. 

The  attractive  force  which  the  earth  exerts  upon  a  body  is  proportioned  to 
its  mass,  or  to  the  quantity  of  matter  contained  in  it,  and  as  weight  is  merely 
the  measure  of  such  attraction,  it  follows  that  a  body  of  a  large  mass  will  be 
attracted  strongly,  and  possess  great  weight,  while,  on  the  contrary,  a  body 
made  up  of  a  small  quantity  of  matter,  will  be  attracted  in  a  less  degree,  and 
possess  less  weight.  We  recognize  this  difference  of  attraction  by  calling 
the  one  body  heavy  and  the  other  light. 

9.  Varieties  of  Force.  —  Mo-lec'ular,  or,  as   they  are 
sometimes  called.  Internal  Forces,  are  distinguished  from 
all  the  other  Forces  which  act  upon  matter,  in  this  respect 
— that  they  act  upon  particles  or  molecules  of  matter  at 
immeasurably  small  distances  only. 

The  forces  developed  through  the  agencies  of  heat, 
light,  electricity,  and  magnetism,  are  diverse  in  their  na- 
ture, and  aifect  different  forms  of  matter  differently.  They 
differ  from  the  force  of  gravitation  inasmuch  as  their  in- 
fluence does  not  appear  to  be  universal  or  constant,  and 
is  apparently  limited  by  distance.  They  differ,  especially, 
from  molecular  forces,  inasmuch  as  their  influence  upon 
matter  is  exerted  at  sensible  distances. 

It  is  not  at  all  certain  that  the  forces  which  act  upon  matter,  as  above  enu- 
merated, are  all  separate  and  independent.  Their  connection  with  each  other 
is  most  intimate,  and  there  is  reason  for  believing  that  some  of  them  are  only 
different  manifestations  of  the  same  agent,  or  principle. 

10.  Molecular  Forces,— Under  the  designation  of  molec'- 
ular  forces  are  especially  included  four  different  manifes- 
tations of  force,  or,  as  they  are  usually  called,  varieties  of 


QTTESTIONB.— What  is  Terrestrial  Gravitation  ?  What  is  Weight »  What  are  the  pecu- 
liarities of  molecular  forces?  What  are  the  peculiarities  of  the  forcer,  developed  by  the 
agencies  of  light,  heat,  electricity,  and  ma<?netism  ?  Is  it  certain  that  the  forces  enu- 
merated are  all  independent  principles  ?  What  are  included  under  the  Lead  of  mole- 
cular forces  ? 


14  PRINCIPLES    OF    CHEMISTRY. 

attraction.     These  are  COHESION,  ADHESION,  CAP'ILLARY 
ATTRACTION,  and  AFFINITY. 

Although  essentially  differing  from  each  other,  these  forces  all  agree  in  one 
remarkable  particular — and  that  is,  their  influence  upon  matter  is  exerted 
only  at  distances  which  are  immeasurable,  or  insensible.  If  the  particles  of 
a  body  are  separated  from  each  other  to  the  slightest  appreciable  degree,  the 
influence  of  these  attractive  forces  is  instantly  neutralized  or  destroyed. 

11.  Cohesion,  or  COHESIVE  ATTRACTION,  is  that  force 
which  binds  together  atoms  of  the  same  kind  of  matter 
to  form  one  uniform  mass. 

The  force  which  holds  together  the  atoms  of  a  mass  of  iron,  wood,  or  stone, 
is  cohesion,  and  the  atoms  are  said  to  cohere  to  each  other. 

The  effort  required  to  break  a  substance  is  a  measure 
of  the  intensity  or  strength  of  the  cohesive  force  exerted 
by  its  particles. 

When  the  Attraction  of  Cohesion  between  the  particles 
of  a  substance  is  once  destroyed,  it  is  generally  impossible 
to  restore  it.  Having  once  reduced  a  mass  of  wood  or  stone 
to  powder,  we  can  not  make  the  minute  particles  cohere 
again  by  merely  pushing  them  into  their  former  position. 

In  some  instances,  however,  this  may  be  accomplished  by  resorting  to  va- 
rious expedients.  Iron  may  be  made  to  cohere  to  iron  by  heating  the  metal 
to  a  high  degree,  and  hammering  the  two  pieces  together.  The  particles 
are  thus  driven  into  such  intimate  contact,  that  they  cohere  and  form  one 
uniform  mass.  This  property  is  called  WELDING,  and  belongs  only  to  two 
metals,  iron  and  platinum. 

12.  Adhesion,  or  Adhesive   Attraction,   is  that  force 
which  causes  unlike  particles  of  matter  to  adhere,  or  re- 
main attached  to  each  other  when  united. 

Dust  floating  in  the  air  sticks  to  the  wall  or  ceiling,  through  the  force  of 
adhesion.  When  we  write  on  a  wall  with  a  piece  of  chalk,  or  charcoal,  the 
particles,  worn  off  from  the  material,  stick  to  the  wall  and  leave  a  mark, 
through  the  force  of  adhesion.  Two  pieces  of  wood  may  be  fastened  to- 
gether by  means  of  glue,  in  consequence  of  the  adhesive  attraction  between 
the  particles  of  the  wood  and  the  particles  of  glue. 

13.  Cap'illary  Attraction  is  that  variety  of  molecular 
force  which  manifests  itself  between  the  surfaces  of  solids 
and  liquids. 


QUESTIONS.— What  is  cohesion?    What  is  a  measure  of  the  force  of  cohesion  ?    What 
is  welding?    What  is  adhesion  ?    Give  examples  of  adhesion.    What  is  capillary  attraction  ? 


INTRODUCTION. 


15 


FIG.  l. 


FIG.  2. 


The  ordinary  definition  of  Cap'illary  Attraction  is,  that  form  of  attraction 
which  causes  liquids  to  ascend  above  their  level  in  capillary  tubes.  This,  how- 
ever, is  not  strictly  correct,  as  this  force  not  only  causes  an  elevation,  but  also 
a  depression  of.  liquids  in  tubes,  and  is  at  work  wherever  fluids  are  in  contact 
with  solid  bodies. 

The  name  "Capillary  Attraction"  originated  from  the  cir- 
cumstance that  this  class  of  phenomena  was  first  observed  in 
small  glass  tubes,  the  bore  of  which  was  not  thicker  than  a 
hair,  and  which  were  hence  called  Capillary  Tubes,  from  tho 
Latin  word  capilla,  which  signifies  a  hair, 

The  simplest  method  of  exhibiting  capillary  attraction  is  to 
immerse  the  end  of  a  piece  of  thermometer  tube  in  water  (see 
Fig.  1)  which  has  been  tinted  with  ink.  The  liquid  will  bo 
seen  to  ascend,  and  will  remain  elevated  in  the  tube  at  a  con- 
siderable height  above  the  surface  of  the  liquid  in  the  vessel. 

The  height  to  which  water  will  rise  in  ca- 
pillary tubes  is  in  proportion  to  the  smallness 
of  their  diameters. 

This  is  clearly  shown  by  the 
following  simple  experiment.  If 
two  plates  of  glass,  A  and  Bf 
Fig.  2,  be  plunged  into  water 
at  their  lower  extremities,  with 
their  faces  vertical  and  parallel, 
and  at  a  certain  distance  asun- 
der, the  water  will  rise  at  the 
~~  ~  points  in  and  nr  where  it  is  in. 

contact  with  the  glass  -r  but  at 

all  intermediate  pointy  beyond  a  small  distance  from  the  plates,  the  general 
level  of  the  surfaces  E,  Cr  and  D,  will  corre- 
spond. 

If  the  two  plates,  A  and  Br  are  brought  near 
to  each  other,  as  in  Fig,  3,  the  two  curves,  m 
and  TO,  will  unite,  so  as  to  form  a  concave  sur- 
face, and  the  water  at  the  same  time  between 
them  will  be  raised  above  the  general  level,  E 
and  D,  of  the  water  in  the  vessel.  If  the 
plates  be  brought  still  nearer  together,  as  in 

Fig.  4,  the  water  between  them  will  rise  still  higher,  the  force  which  sustains 
the  column  being  increased  as  the  distance  between  the  plates  is  diminished. 
Illustrations  of  capillary  attraction  are  most  familiar  in  the  experience  of 
every-day  life.     The  wick  of  a  lamp,  or  candle,  lifts  the  oil,  or  melted  grease 

QiTESTiONg. — How  may  the  phenomena  of  cap'fllary  attraction  he  illustrated  ?  To-  -what 
height  will  water  rise  in  capillary  tuhes  ?  What  are  familiar  examples  of  capillary  at- 
traction ? 


FlG.  3, 


16  PRINCIPLES     OF     CHEMISTRY. 

which  supplies  the  flame  from  a  surface 
often  two  or  three  inches  below  the  point 
of  combustion. 

When  one  end  of  a  sponge,  or  a  lump  of 
sugar  is  brought  into  contact  with  water, 
the  liquid,  by  capillary  attraction,  will  rise, 
or  soak  up  above  its  level,  into  the  interior 
of  the  sponge,  or  sugar,  until  all  its  pores 
are  filled. 

14.  Affinity  is  that  variety  of  molec'ular  force  or  attrac- 
tion which  unites  atoms  of  unlike  substances  into  com- 
pounds possessing  new  and  distinct  properties. 

Oxygen,  for  example,  unites  with  iron,  and  forms  oxyd  of  iron,  or  iron- 
rust,  a  substance  possessing  different  and  distinct  properties  from  either  iron 
or  oxgyen.  In  like  manner,  oxygen  and  hydrogen,  two  gases  not  to  be  dis- 
tinguished in  appearance  from  common  air,  unite  to  form  water,  a  liquid. 

When  the  particles  of  different  substances  are  united  together  by  the  force 
of  affinity,  the  compound  formed  possesses  properties  entirely  different  from 
that  of  its  constituents,  and  in  no  respect  resembles  a  mixture,  which  is 
merely  a  mechanical  union  of  bodies — as  when  salt  is  mixed  with  sand.  The 
forces  of  adhesion  or  capillary  attraction  may  closely  unite  unlike  particles  of 
matter  together,  but  they  do  not  effect  any  change  in  the  nature  or  properties 
of  the  particles  acted  upon.  Affinity,  on  the  contrary,  entirely  changes  the 
properties  of  the  unlike  particles  which  it  unites,  and  by  so  doing  produces 
combinations  which  possess  entirely  different  qualities. 

The  action  of  gravity  and  of  the  several  molecular  forces  may  be  illustrated 
by  referring  to  a  particular  form  of  matter,  as,  for  example,  water.  The  force 
of  affinity  binds  together  the  atoms  of  the  elements,  oxygen  and  hydrogen,  to 
constitute  an  atom,  or  molecule  of  water;  cohesion  unites  the  particles  of 
water  thus  formed  into  drops,  or  larger  masses ;  adhesion  causes  the  union  of 
•water  with  the  surfaces  of  different  substances,  thereby  producing  the  pheno- 
menon which  we  call  ;s  wetting;"  capillary  attraction  causes  water  to  rise 
above  its  level,  or  "  soak  up"  as  it  is  termed,  in  a  sponge,  or  other  porous 
substance ;  while  the  force  of  gravity  causes  coherent  quantities  of  water  to 
fall  as  rain,  or  to  move  down  inclined  surfaces  in  the  form  of  rivers,  brooks,  etc. 

15.  Repulsion, — In  opposition  to  the  several  attractive 
forces  which  act  upon  matter,  a  repulsive  force  also  ex- 
ists, the  tendency  of  which  is  to  separate  the  particles  of 
matter  from  one  another. 


QTTKSTIONB.— What  is  affinity  ?  What  are  illustrations  of  affinity  ?  How  do  the  com- 
pounds of  matter  formed  through  the  force  of  affinity  differ  from  a  mixture  ?  How  do 
the  forces  of  adhesion  and  capillary  attraction  differ  from  affinity  ?  How  may  the  ac- 
tion of  gravity  and  the  molecular  forces  be  illustrated  ?  What  force  acts  in  opposition  to 
the  attractive  forces  ? 


INTRODUCTION.  17 

The  resistance  experienced  in  attempting  to  compress  a  substance  is  the 
result  of  the  opposition  of  the  repulsive  force  which  pervades  its  particles 
and  the  effort  required  to  effect  a  compression  is  a  measure  of  the  intensity 
of  the  repulsive  force. 

A  dew-drop  resting  upon  a  leaf  is  not  in  actual  contact  with  its  surface, 
but  is  sustained  at  a  little  distance  above  it  by  the  force  of  repulsion.  In- 
genious experimentation  has  proved  that  when  two  glasses,  one  slightly  con- 
vex and  the  other  flat,  are  placed  upon  each  other,  and  pressed  together  with 
a  force  of  1,000  pounds  to  the  square  inch,  they  still  remain  at  a  distance 
from  each  other  of  the  thickness  of  the  top  of  a  soap-bubble  before  it  bursts, 
or  at  least  l-4450th  of  an  inch.  If  we  compress  a  certain  quantity  of  gas,  as 
common  air,  and  then  allow  it  to  dilate,  by  removing  ah1  restraint,  it  will  ex- 
pand without  limit,  and  fill  every  really  empty  space  which  is  open  to  it. 
This  takes  place  through  the  agency  of  an  internal  repulsive  force,  which 
tends  to  drive  the  particles  from  one  another. 

It  is  not  definitely  known  whether  the  repulsive  force,  which  appears  to 
influence,  under  certain  circumstances,  the  particles  of  all  matter,  is  a  separate 
and  independent  principle,  or  whether  it  is  the  result  of  the  action  of  heat  or 
of  electricity,  or  of  both  these  forces  combined.  Heat,  in  its  influence  upon 
matter,  always  acts  as  a  repulsive  force,  and  is  always  opposed  to  the  influ- 
ence of  cohesion. 

16.  Elasticity, — That  property  of  bodies  known  as  Elas- 
ticity is  the  result  of  the  joint  action  of  the  repulsive  and 
attractive  forces  ;  and  substances  are  said  to  be  more  or 
less  elastic,  according  to  the  facility  with  which  they  re- 
gain their  original  form  and  dimension  after  the  force 
which  has  compressed  or  extended  them  is  removed. 

17.  Three  Forms  of  Matter,— According  as  the  attractive 
or  repulsive  forces  prevail,  all  bodies  will  assume  one  of 
three  forms  or  conditions — the  SOLID,  the  LIQUID,  or  the 
A'ER-I-FORM,*  or  GASEOUS  condition. 

18.  Solids, — A  solid  body  is  one  in  which  the  particles 
are  so  strongly  held  together  by  the  attractive  force  of 
cohesion,  that  the  body  maintains  its  form  or  figure  under 
all  ordinary  circumstances. 

If  the  force  of  cohesion  acted  exclusively  upon  matter,  every  substance 
•would  possess  insuperable  solidity,  hardness,  and  tenacity. 


A'er-i-form,  having  the  form,  or  resemblance,  of  air. 


QTTESTIONB. — What  evidence  is  there  of  the  existence  of  a  repulsive  force?  What  is 
elasticity?  What  are  illustrations  of  the  influence  of  a  repulsive  force?  Under  what 
three  forms  or  conditions  does  matter  exist  ?  What  is  a  solid  body  ? 


18  PRINCIPLES    OF     CHEMISTRY. 

19.  Liquids , — A  liquid  body  is  one  in  which  the  particles 
of  matter  are  held  together  so  slightly  by  the  force  of  co- 
hesion that  they  move  upon  each  other  with  the  greatest 
facility. 

Hence  a  liquid  can  never  be  made  to  assume  any  particular  form  except 
that  of  the  vessel  in  which  it  is  inclosed. 

20.  Gaseous-  Bodies, — An  a'er-i-form  or  gaseous  body  is 
one  in  which  the  particles  of  matter  are  not  held  together  by 
any  force  of  cohesive  attraction,  and  but  for  the  restrain- 
ing influence  of  the  force  of  gravity  would  entirely  sepa- 
rate and  move  off  from  one  another. 

A  gaseous  body  is  generally  invisible,  and,  like  the  air  surrounding  us, 
affords  to  the  sense  of  touch  no  evidence  of  its  existence  when  in  a  state  of 
complete  repose.  Gaseous  bodies  may  be  confined  in  vessels,  whence  they 
exclude  liquids,  or  other  bodies,  thus  demonstrating  their  existence,  though 
invisible,  and  also  their  impenetrability. 

21.  Change  of  Condition  . — Most  substances  can  be  made  to  assume 
successively  the  form  of  a  solid,  a  liquid,  or  a  gas.     In  solids,  the  attractive 
force  is  the  strongest ;  the  particles  keep  their  places,  and  the  solid  retains  its 
form.     But  if  we  heat  a  solid  body,  as  for  example  a  piece  of  ice,  or  sulphur,  we 
weaken  the  force  of  cohesion  which  binds  the  particles  together,  and  allow 
the  repulsive  force  to  prevail;  the  particles  of  the  solid  thereby  become  mov- 
able upon  themselves,  and  we  say  the  body  melts,  or  becomes  liquid.     In 
liquids  the  attractive  and  repulsive  forces  are  nearly  balanced,  but  if  we  sup- 

5<  ply  an  additional  quantity  of  heat,  we  de- 

stroy the  attractive  force  altogether,  and 
increase  the  repulsive  force  to  soch  an  ex- 
tent that  the  liquid  assumes  the  form  of  a 
gas,  or  vapor,  in  which  the  separate  par- 
ticles tend  to  fly  off  from  each  other.  By 
reversing  the  process,  or,  in  other  words, 
by  withdrawing  the  heat,  we  can  diminish 
or  destroy  the  repulsive  force,  and  cause 
the  attractive  force  again  to  predominate — 
the  body  returning  to  its  former  conditions, 
first  of  a  liquid,  then  of  a  solid. 

The  power  of  the  repulsive  force  gen- 
erated by  heat  is  strikingly  illustrated  in 
the  conversion  of  water  into  steam.  In  a  cubic  inch  of  water  converted  into 
steam,  the  particles  will  repel  each  other  to  such  an  extent,  that  the  space 

QUESTIONS — What  is  a  liquid  ?  What  is  an  a'er-i-form,  or  gaseous  body  ?  Under  what 
circumstances  will  a  body  assume  the  form  of  a  solid,  a  liquid,  or  a  gas  ?  What  experi- 
ment illustrates  the  repulsive  power  of  heat. 


INTRODUCTION.  19 

occupied  by  the  steam  will  be  1700  times  greater  than  that  occupied  by  the 
water.  Fig.  5  illustrates  the  comparative  difference  between  the  bulk  of  steam 
and  the  bulk  of  water. 

22.  Ethereal  Condition  » — Recent  investigations  in  science  have  ren- 
dered it  probable,  that  matter,  in  addition  to  the  three  separate  states  or  con- 
sistencies in  which  it  is  ordinarily  presented  to  us — solid,  liquid,  and  gaseous — 
exists  also  in  a  fourth  state,  which  is  called  the  ethereal.    It  is  supposed  that 
all  space — that  existing  between  the  planets  and  other  heavenly  bodies^ 
equally  with  that  existing  between  the  atoms,  or  molecules  of  every  sub- 
stance, even  the  most  dense — is  pervaded  by  an  extremely  rare,  imponder- 
able, and  highly  elastic  medium,  or  fluid  'form  of  matter,  termed  ETHER. 
This  substance,  like  air,  is  believed  to  be  capable  of  motion,  and  of  receiving 
and  transmitting  vibrations,  which  vibrations  by  their  action  on  the  ordinary 
forms  of  matter,  are  supposed  to  produce  the  phenomena  of  heat,  light,  elec- 
tricity, etc.,  in  the  same  manner  as  the  vibrations  of  air  occasioned  by  a 
sounding  body  produce  the  phenomena  of  sound. 

23.  Matter  Indestructible, — All  the  researches  and  in- 
vestigations of  science  teach  us  that  it  is  impossible  by  nat- 
ural operations,  to  either  create  or  destroy  a  single  particle 
of  matter.     The  power  to  create  and  destroy  matter  belongs 
to  the  DEITY  alone.     The  quantity  of  matter  which  exists, 
in  and  upon  the  earth  has  never  been  diminished  by  the 
annihilation  of  a  single  atom. 

When  a  body  is  consumed  by  fire,  there  is  no  destruction  of  matter :  it  has 
only  changed  its  form  and  position.  When  an  animal  or  vegetable  dies  and 
decays,  the  original  form  vanishes,  but  the  particles  of  matter,  of  which  it  was 
once  composed,  have  merely  passed  off  to  form  new  bodies  and  enter  into  new 
combinations. 

24.  Force  Indestructible, — Kecent    investigations    in 
science  seem  to  prove  that  force  is  equally  as  indestructible 
as  matter  ;  or,  in  other  words,  that  there  is  no  such  thing 
as  a  destruction  of  force  ;  consequently  the  amount  of  force 
in  operation  in  the  earth,  and  possibly  throughout  the 
universe,  never  varies  in  quantity,  but  remains  always  the 
same. 

Some  of  the  reasons  which  have  led  to  a  belief  in  the  indestructibility  of 
force  may  be  stated  as  follows : — 

The  only  mode  in  which  we  can  judge  of  the  existence  of  a  force  is  from 
the  effects  it  produces,  and  of  these  effects,  that  which  is  the  most  evident  to 

QUESTIONS. — What  Is  the  supposed  ethereal  condition  of  matter,  or  what  are  the  peculi- 
arities of  matter  in  this  condition?  Is  matter  indestructible?  Is  force  indestructible? 
What  reasons  induce  us  to  believe  that  a  force  can  not  be  destroyed  ? 


20  PRINCIPLES    OF     CHEMISTRY. 

our  senses  is  the  power  either  of  producing  motion,  of  arresting  it,  or  of  alter- 
ing its  direction :  whatever  is  capable  of  effecting  these  results  is  considered 
as  a  form  of  force.  Motion,  therefore,  may  be  considered  as  the  indicator  of 
force,  and  wherever  we  perceive  motion,  we  may  be  certain  that  some  force  is 
operating.  Now  it  will  be  found,  that  hi  all  cases  in  which  work  is  performed 
—or,  to  state  it  in  other  words,  in  all  cases  in  which  force  is  exerted  and  ap- 
parently made  to  disappear — that  it  has  expended  itself  either  in  setting  into 
action  some  other  force,  or  else  it  has  produced  a  definite  and  certain  amount 
of  motion.  This  motion  when  used  will  again  give  rise  to  an  equal  amount 
of  the  force  which  originally  produced  it.  For  example,  we  burn  coal  in  the 
air ;  the  force  of  affinity  causes  the  particles  of  coal  to  unite  with  the  oxygen 
of  the  air ;  the  coal  changes  its  form,  and  a  quantity  of  heat  remains,  which 
heat  represents  the  chemical  force  expended.  The  heat  thus  developed  is  now 
ready  to  do  work :  it  may  be  employed  in  converting  water  into  steam,  and 
the  steam  so  obtained  can,  through  the  medium  of  machinery,  be  applied  to 
the  production  of  motion.  Motion  may  again  be  made  to  produce  heat — as 
through  friction,  for  example — and  recent  experiments  seem  to  show  that  the 
amount  of  heat  so  developed  by  motion,  would,  if  collected  and  measured, 
prove  to  be  equal  in  amount  to  that  which  produced  the  motion.  The  heat 
produced  by  motion  is  generally  dissipated  and  lost  for  practical  purposes,  but 
it  is  not  absolutely  lost.  It  has  been  absorbed,  or  diffused  through  space,  or 
converted  into  some  other  form  offeree,  which  in  turn  takes  part  in  some  of 
the  great  operations  of  nature,  or  again  ministers  to  the  wants  and  necessities 
of  man.  Numerous  other  facts  in  support  of  the  view  that  force,  like  matter, 
changes  but  is  never  destroyed,  might  be  adduced.  The  subject  is  one  of 
great  interest,  and  has  a  practical  bearing  on  many  of  the  operations  of  chem- 
istry. 

25.  Classification  of  Forces,—  All  the  changes  which  take  place  in 
matter  through  the  agency  of  the  several  forces  which  act  upon  it  are  considered 
under  three  general  divisions,  or  departments  of  science,  viz.,  Physics,  or 
Natural  Philosophy,  Animal  and  Vegetable  Physiology,  and  Chemistry. 

26.  Natural  Philosophy,— Physics,  or  Natural  Philoso- 
phy, is  that  department  of  science  which  considers  generally, 
all  those  changes  and  phenomena  which  are  observed  to  take 
place  in  matter  through  the  agency  of  the  forces  of  gravi- 
tation, cohesion,  adhesion,  capillary  attraction,  molecular 
repulsion,  light,  heat,  electricity,   and   magnetism,  and 
these    several    forces    have   been  termed   the    Physical 
Forces. 

27.  Physiology,— Animal  and  Vegetable  Physiology  is 


QUESTIONS. — Under  what  three  general  divisions  are  the  forces  which  act  upon  matter 
considered  ?  What  forces  are  considered  under  the  department  of  Natural  Philosophy  T 
What  forces  under  the  department  of  Animal  and  Vegetable  Physiology? 


INTRODUCTION.  21 

department  of  science  which  treats  of  the  changes  and 
phenomena  observed  to  take  place  in  matter  through  the 
agency  of  the  vital  force. 

28.  Chemistry,— Chemistry  is  that  department  of  science 
which  relates  exclusively  to  all  those  changes  and  pheno- 
mena which  take  place  in  matter  through  the  agency  or 
influence  of  the  force  of  affinity. 

29.  Chemical  Action,— Chemical  Action  is  the  term  used 
to  designate  all  those  operations — the  result  of  the  force  of 
affinity — by  which  the  form,  solidity,  color,  taste,  smell,  and 
action  of  substances  become  changed  ;  so  that  new  bodies, 
with  quite  different  properties,  are  formed  from  the  old. 

30.  Properties  of  Matter,— The  properties  which  char- 
acterize material  objects  in  general,  may  be  classed  under 
two  heads,  viz.,  physical  and  chemical  properties. 

Physical  Properties , — The  Physical  Properties  of  an  ob- 
ject are  those  by  which  it  is  most  readily  defined,  or  dis- 
tinguished from  some  other  object.  The  form  of  a  body ;  its 
condition  as  a  solid,  a  liquid,  or  a  gas  ;  its  color,  hardness, 
tenacity,  and  its  relations  to  heat  and  electricity,  are  ex- 
amples of  its  physical  properties.  Physical  properties  are 
independent  of  the  action  which  the  body  exerts  upon 
other  bodies. 

Chemical  Properties, — The  Chemical  Properties  of  a 
body  are  those  which  relate  essentially  to  its  action  upon 
other  bodies,  and  to  the  changes  which  the  body  either 
experiences  itself,  or  causes  to  take  place  in  other  bodies 
by  contact  with  them. 

The  physical  properties  of  such  a  substance  as  sulphur,  are,  its  peculiar  odor, 
its  yellow  color,  its  brittleness,  its  crystalline  structure,  its  specific  gravity,  the 
facility  with  which  it  exhibits  electrical  attraction  when  rubbed,  and  the  like 
similar  qualities,  all  of  which  are  independent  in  a  great  degree  of  each  other, 
and  are  so  distinctive  in  their  character  that  our  senses  inform  us  at  once 
that  the  substance  in  question  is  sulphur,  and  not  some  other  form  of  matter. 

If  we  would  now  enumerate  the  chemical  properties  of  sulphur,  it  would 

QUESTIONS. — What  is  chemistry?  Define  chemical  action.  Under  what  two  heads 
may  the  properties  of  material  objects  be  classed?  What  are  the  physical  properties 
of  a  body  ?  What  are  chemical  properties  ?  Illustrate  the  distinction  between  the 
physical  and  chemical  properties  of  sulphur. 


22  PRINCIPLES     OF     CHEMISTRY. 

be  necessary  to  refer  to  those  operations  by  which  the  body  becomes  changed 
and  loses  its  distinctive  character — such  as  the  ease  with  which  it  takes  fire, 
its  insolubility  in  water,  and  its  solubility  in  oil  of  turpentine,  and  the  ra- 
pidity with  which  it  unites  with  iron,  silver,  copper,  and  many  other  of  the 
metals. 

Had  there  been  but  one  kind  of  matter  in  the  universe,  it  could  have  pos- 
sessed only  physical  properties,  and  the  laws  of  Natural  Philosophy  would 
have  explained  all  the  phenomena  and  changes  which  could  possibly  have 
taken  place  in  it.  As  the  character  or  composition  of  this  one  form  of  mat- 
ter, moreover,  could  not,  under  the  circumstances,  have  been  changed  by  the 
action  of  any  different  substance  upon  it,  it  could  not  have  possessed  any 
chemical  properties,  and  no  idea  could  have  been  formed  by  an  intelligent 
being  of  any  such  department  of  knowledge  as  chemistry. 

The  connection,  however,  between  Chemistry  and  Natural  Philosophy  ig 
most  intimate ;  and  all  chemical  changes  are  influenced  to  such  an  extent  by 
the  action  of  the  physical  forces,  that  a  knowledge  of  the  principles  of  Nat- 
ural Philosophy  is  requisite  for  a  proper  understanding  of  the  nature  of 
chemical  phenomena.  Especially  i§  this  the  case  as  respects  the  forces  mani- 
fested through  the  agency  of  Heat,  Light,  Electricity,  and  Magnetism ;  and  a 
brief  review  of  these  subjects  is  generally  regarded  as  a  necessary  introduction 
to  the  study  of  the  science  of  Chemistry.  The  first  part  of  this  work  is  there- 
fore devoted  to  a  consideration  of  the  nature  and  action  of  the  physical  forces 
so  far  as  they  are  concerned  in  producing  chemical  changes,  or  in  character- 
izing chemical  phenomena.* 


CHAPTER   I. 

ON   THE   CONNECTION    OF   GRAVITY,    COHESION,    ADHESION, 
AND   CAPILLARY   ATTRACTION   WITH    CHEMICAL   ACTION. 

SECTION    I. 

GE  AVITY. 

31.  Connection  of  Gravity  with  Chemical  Phenomena,— 
The  influence  of  the  force  of  gravity  on  matter  is  never 

*  It  has  been  assumed,  in  the  preparation  of  this  work,  that  the  student  is  conversant 
•with  the  general  principles  of  Natural  Philosophy,  and  no  attempt  has  therefore  been 
made  to  treat  the  subjects  of  Heat,  Light,  Electricity,  and  Magnetism  in  any  other  than 
a  general  manner,  and  with  special  reference  to  their  connection  with  chemical  pheno- 


.— "What  connection  is  there  between  Natural  Philosophy  and  Chemistry  ? 
Is  gravity  influenced  by  changes  in  the  condition  of  matter  ? 


WEIGHT.  23 

affected  by  any  change  which  may  take  place  in  the  form 
or  condition  of  the  matter  itself. 

A  pound  of  water  is  attracted  by  the  influence  of  gravity  toward  the  cen- 
ter of  the  earth  with  a  certain  degree  of  force,  and  as  weight  is  the  measure 
of  gravity,  we  express  the  exact  amount  of  this  attractive  force,  by  saying 
that  the  water  weighs  a  pound.  If  we  deprive  this  particular  quantity  of 
water  of  heat,  sufficient  to  freeze  and  convert  it  into  ice — a  solid — it  will 
still  weigh  a  pound ;  if  we  convert  the  same  quantity  of  water  into  steam  by 
the  addition  of  heat,  it  will  occupy  a  space  seventeen  hundred  times  greater 
than  before — yet  the  steam  produced  will  be  attracted  by  the  force  of  gravity 
equally  with  the  water  from  which  it  is  derived,  and  will  continue  to  weigh  a 
pound. 

As  the  action  of  gravity,  therefore,  is  never  suspended,  and  as  the  smallest 
particle  of  matter  can  not  be  annihilated  by  any  operation,  we  are  enabled  to 
test  the  accuracy  of  every  chemical  process,  and  ascertain  the  true  composition 
of  bodies  by  proving  the  weight  of  the  compound  to  be  equal  to  the  weight 
of  the  substances  which  produce  it. 

32.  Use  of  the  Balance.— The  balance  is  to  the  chemist 
what  the  compass  is  to  the  mariner,  and  before  its  intro- 
duction as  a  means  of  verifying  experiments,  the  whole 
science  of  Chemistry  was  a  collection  of  disconnected  and 
separate  facts  and  theories. 

Until  within  a  comparatively  recent  period  it  was  supposed  that  common 
air,  or  gases,  did  not  possess  weight ;  and  this  error,  which  was  necessarily 
accompanied  with  most  absurd  notions  respecting  the  constitution  of  air  and 
gases,  prevailed  until  the  experiment  of  weighing  them  was  tried,  when 
they  were  found  to  be  attracted  by  gravity  equally  with  all  other  kinds  of 
matter. 

Less  than  a  hundred  years  ago  it  was  generally  taught  and  believed  that 
when  a  body  was  burned,  a  portion  of  its  substance  was  lost.  Lavoisier, 
an  eminent  French  philosopher,  proved  the  contrary  by  carefully  burning  a 
body,  and  then  weighing  all  that  was  left  unconsumed  by  the  fire,  and  all 
the  invisible  products  that  escaped.  He  found,  that  instead  of  there  being 
a  loss  of  matter,  there  was  a  gain,  and  thus  by  a  simple  experiment  overthrew 
at  once  ideas  respecting  the  nature  of  fire  and  combustion  that  had  prevailed 
for  centuries  previous. 

The  great  distinction,  according  to  Professor  Liebig,  between  Chemistry  and 
Natural  Philosophy,  is  that  the  one  weighs  and  the  other  measures.  ' 

33.  Two  Great  Systems  of  Weights,— Two  great  systems 
of  weights  are  recognized  throughout  the  civilized  world  in 

, 1 -        

QUESTIONS — Give  an  illustration.  What  relation  does  the  balance  sustain  to  the  opera- 
tions of  the  chemist  ?  What  facts  illustrate  the  use  of  the  balance  in  effecting  chemicaJ 
discoveries  ?  What  two  systems  of  weights  are  recognized  ? 


24  PRINCIPLES     OF     CHEMISTRY. 

Chemistry  and  in  all  other  operations.     These  are  known 
as  the  English  and  French  Systems. 

34.  The  English  System  of  Weights,— The  smallest  de- 
nomination of  weight  made  use  of  in  the  English  System 
(the  one  generally  used  in  the  United  States)  is  a  grain. 
The  Parliament  of  England  passed  a  law  in  1286,  that 
32  grains  of  wheat,  well  dried,   should  weigh  a  penny- 
weight.    Hence  the  name  grain  applied  to  this  measure 
of  weight. 

It  was  afterward  ordered  that  a  pennyweight  should  be  divided  into  only 
24  grains.  Grain  weights  for  practical  purposes  are  made  by  weighing  a  thin 
plate  of  metal  of  uniform  thickness,  and  cutting  out,  by  measurement,  such  a 
proportion  of  the  whole  as  will  weigh  one  grain.  In  a  like  manner,  weights 
may  be  obtained  for  chemical  purposes  which  weigh  only  the  1,000th  part  of 
a  grain. 

Seven  thousand  grains  constitute  a  pound  avoirdupois, 
and  from  this  pound  all  measures  of  capacity  have  been 
derived  by  Act  of  the  English  Parliament. 

Thus  a  standard  gallon  is  by  law  as  much  distilled  water  as  will  weigh  ten 
pounds,  or  70,000  grains;  and  a  measure  holding  exactly  this  quantity  of 
water  is  a  gallon  measure.  By  subdividing  the  gallon  we  obtain  smaller 
measures,  quarts,  pints,  etc. 

35.  French  System  of  Weights,— The  French  System  of 
Weights  is  constructed  on  a  different  plan,  and  is  distin- 
guished for  its  great  simplicity — all  its  divisions  being 
made  by  ten.     It  is,  therefore,  sometimes  called  the  deci- 
mal system. 

On  the  continent  of  Europe  this  system  of  weights  is  almost  universally 
adopted  for  all  scientific  operations,  and  is  gradually  being  introduced  into 
England  and  the  United  States.  It  is,  therefore,  highly  important  that  the 
principles  upon  which  it  is  based  should  be  understood. 

The  basis  of  the  French  System  is  an  invariable  dimen- 
sion of  the  globe,  viz.,  a  fourth  part  of  the  earth's  merid- 
ian, or  a  fourth  part  of  a  circle  passing  round  the  earth 
(lengthwise),  and  intersecting  at  the  poles. 


QUESTIONS — What  is  the  smallest  weight  recognized  in  the  English  System  ?  What 
is  a  pound  avoirdupois?  How  are  measures  of  capacity  derived  from  measures  of 
weight?  What  is  an  English  gallon?  What  is  the  distinguishing  peculiarity  of  the 
French  system  of  weights  ?  Where  is  the  French  system  used  ?  What  is  its  basis  ? 


WEIGHT. 


25 


FIG.  6.  The  circle  N  E  S  W,  Fig.  6,  represents  a 

meridian  of  the  earth ;  and  a  fourth  part  of 
this  circle,  or  the  distance  N  E,  constitutes 
the  dimension  on  which  the  French  System 
is  founded. 

This  distance,  which  was  accu- 
rately measured,  is  divided  into 
ten  million  equal  parts  ;  and  a 
single  ten  millionth  part  adopted 
as  a  measure  of  length,  and  called 
a  metre. 

A  metre  is  about  three  feet  and  a  quarter  in  length,  or  about  thirty-nine 
English  inches.  By  multiplying  or  dividing  the  metre  by  ten,  all  the  larger 
and  smaller  measures  of  length  are  obtained.  For  indicating  measures  smaller 
than  a  metre,  Latin  terms  are  used ;  for  indicating  measures  larger  than  a 
metre,  Greek  terms.  Thus — 


Smaller  Measures. 
Metre. 

Decimetre  =  l-10th  metre. 
Centimetre=  1 -1 00 th  metre. 
Millimetre  =l-1000th  metre. 


Larger  Measures. 
Metre. 

Decametre  =  10  metres. 
Hectometre=  100  metres. 
Kilometre  =  1,000  metres. 
Myriametre=10,000  metres. 


The  system  of  weights  was  formed  from  measures  of  length  in  the  follow- 
ing manner.  A  box,  in  the  form  of  a  cube,  was  taken,  measuring  one  centi- 
metre .in  every  direction.  This,  filled  with  distilled  water  at  its  greatest 
density  (at  a  temperature  of  39°  Fahrenheit's  thermometer),  was  taken  as  the 
unit  of  the  decimal  weights,  and  called  a  gramme* — a  quantity  equal  to  about 
fifteen  English  grains.  The  gramme,  multiplied  and  divided  by  ten,  gives  all 
the  other  larger  or  smaller  weights.  Thus — 


Smaller  Weights. 
Gramme. 

Decigramme  =  l-10th  gramme. 
Centigramme=  l-100th  grammt . 
Milligramme  =1  - 1 , 0  0  Oth  gramme. 


Larger  Weights. 
Gramme. 

Decagramme  =  1-0  grammes. 
Hectogramme^  100  grammes. 
Kilogramme  ===  1,000  grammes. 
Myriagramme=l  0,000  grammes. 


The  kilogramme  corresponds  in  its  use  in  all  commercial  transactions  with 
the  English  pound.     Its  weight  is  equal  to  about  2  J  pounds  avoirdupois. 


Pronounced  Gram. 


QUESTIONS.— What  is  the  Metre  of  the  French  system?  How  are  the  larger  and 
smaller  measures  of  length  derived  from  the  Metre  ?  How  is  the  system  of  weights  de- 
rived from  the  measures  of  length?  What  is  a  Kilogramme? 

2 


26  PRINCIPLES     OF     CHEMISTRY. 

36.  Construction  of  FIG.  7. 
the  Balance.— The  bal- 
ance used  for  all  deli- 
cate   chemical   experi- 
ments is  constructed  in 

the  most  .perfect  man- 
ner. The  point  of  sup- 
port of  the  beam  (see  Fig.  7)  is  a  wedge  of  hardened 
steel  with  a  sharp,  knife-like  edge,  which  rests  upon  a  flat 
plate  of  polished  agate.  The  points  of  support  of  the  two 
scale-pans  are  often  constructed  in  a  similar  manner. 

In  all  nice  experiments  the  balance  must  be  screened  from  currents,  of  air, 
and  the  bodies  weighed  must  have  nearly  the  same  temperature  as  that  of  the 
surrounding  atmosphere — otherwise  currents  of  airT  ascending  and  descending, 
will  be  produced,  which  will  impair  the  accuracy  of  the  weight. 

Balances  are  at  the  present  time  constructed  for  chemical  operations,  so 
delicate  and  exact,  that  they  are  able  to  indicate  the  weight  of  a  thousandth 
part  of  a  grain. 

For  the  experiments  described  in  this  book,  a  common  apothecaries'  balance 
is  all  that  is  requisite. 

37.  Weight  Compared  with  Bulk,— If  equal  bulks  of  matter  of 
different  kinds  be  compared  together,  they  will  be  found  to  diflcr  greatly  in 
weight.     Platinum,  the  heaviest  body  known,  is  upward  of  200,000  times  as 
dense,  bulk  for  bulk,  as  hydrogen. 

Specific  Gravity. — The  specific  gravity,  or  specific  weight 
of  a  body,  is  its  weight  as  compared  with  the  weight  of 
an  equal  bulk  of  some  other  substance,  assumed  as  the 
standard  of  comparison. 

Absolute  Weight,— The  absolute  weight  of  a  body  is  the 
weight  of  its  entire  mass,  considered  without  any  reference 
to  its  bulk,  or  volume. 

The  weight  of  a  body,  as  determined  by  the  ordinary  process  of  weighing, 
is  its  absolute  weight. 

Pure  water,  at  a  temperature  of  60°  Fahrenheit,  has  been  selected  as  the 
standard  for  comparing  the  weights  of  equal  bulks  of  different  solids  and 
liquids ;  and  common  air,  dry,  and  at  a  temperature  of  60°  Fahrenheit,  and 


QUESTIONS.— What  are  the  peculiarities  of  the  balance  as  used  for  chemical  investiga- 
tions ?  What  precautions  are  to  be  observed  in  nice  experiments  ?  How  do  equal  bulks 
of  different  substances  compare?  What  ia  specific  gravity,  or  specific  weight ?  What 
la  absolute  weight  ? 


WEIGHT. 


27 


FIG.  8. 


30  inches  pressure  of  the  barometer,  as  the  standard  for  comparing  the  weights 
of  equal  volumes  of  different  gases  and  vapors. 

Attention  is  given  to  temperature,  and  to  the  pressure  of  the  atmosphere, 
because  the  bulk  of  all  substances  sensibly  varies  with  changes  in  these  con- 
ditions. 

Water  having  been  selected  as  the  standard  of  comparison,  the  question  to 
be  settled  in  the  determination  of  the  specific  gravity  of  a  body  is  simply  this 
— how  much  heavier  or  lighter  is  a  given  bulk  of  a  substance,  than  an  equal 
bulk  of  water  ?  The  solution  of  the  problem  may  be  found  by  the  following 
general  rule  : 

38.  Weigh  first  the  body  in  air,  and  afterward  weigh  it 
when  suspended  in  water.  It  will  be  observed  to  weigh 
less  in  water  than  in  air.  Subtract  the  weight  in  water 
from  the  weight  in  air,  and  divide  the  weight  in  air  by 
the  difference  ;  the  quotient  will  be  the  specific  gravity 
required. 

This  rule  is  based  upon  the  fact,  that 
a  solid  when  weighed  in  water  loses 
weight  equal  to  the  water  it  displaces ; 
and  the  bulk  of  the  water  displaced  is 
exactly  equal  to  its  own. 

Suppose  a  piece  of  gold  weighs  in  the 
air  19  grains,  and  in  water  18  grams; 
the  loss  of  weight  in  water  will  be  1 ; 
19-7-1=19,  the  specific  gravity  of  gold. 

Fig.  8  represents  the  arrangement  of 
the  balance  for  taking  specific  gravities, 
and  the  manner  of  suspending  the  body 
in  water  from  the  scale-pan,  or  beam, 
by  means  of  a  fine  thread,  or  hair. 

39.  The  specific  gravity  of 
Liquids  is  easily  determined  in 
the  following  manner.  A  bottle  capable  of  holding  ex- 
actly 1,000  grains  of  distilled  water  is  obtained,  filled  with 
water,  and  balanced  upon  the  scales.  The  water  is  then 
removed,  and  its  place  supplied  with  the  liquid  whose  spe- 
cific gravity  we  wish  to  determine,  and  the  bottle  and  con- 
tents again  weighed.  The  weight  of  the  fluid,  divided  by 
the  weight  of  the  water,  gives  the  specific  gravity  required. 


QUESTIONS. — What  are  the  standards  of  specific  gravity  ?  How  may  the  specific  gravity 
of  solids  be  determined  ?  Upon  what  principle  is  this  rule  founded  ?  How  may  the  specific 
gravity  of  liauids  be  determined  ? 


28 


PRINCIPLES    OF    CHEMISTRY. 


PIG.  9. 


Thus,  a  bottle  holding  1,000  grains  of  distilled  water,  will  hold  1,845  grains 
of  sulphuric  acid ;  1,845-3*1,000— <1.845,  the  specific  gravity  of  sulphuric  acid ; 
or  this  liquid  is  1,845  times  heavier  than  an  equal  bulk  of  water. 

40.  The  specific  gravity  of  liquids  may  also  be  obtained  without  the  aid  of 
a  balance,  by  means  of  an  instrument  called  the  HYDROMETER. 

The  Hydro 'meter, — This  consists  of  a  hol- 
low glass  tube,  on  the  lower  part  of  which 
a  spherical  bulb  is  blown,  the  latter  being 
filled  with  a  suitable  quantity  of  small 
shot,  or  quicksilver,  in  order  to  cause  it 
to  float  in  a  vertical  position.  The  upper 
part  of  the  tube  contains  a  scale  gradu- 
ated into  suitable  divisions.  (See  Fig.  9.) 

It  is  obvious  that  the  hydrometer  will  sink  to  a  greater 
or  less  depth  in  different  liquids  ;  deeper  hi  the  lighter 
ones,  or  those  of  small  specific  gravity,  and  not  so  deep 
in  those  which  are  denser,  or  which  have  great  specific 
gravity.     The  specific  gravity  of  a  liquid  may,  there- 
fore, be  estimated  by  the  number  of  divisions  on  the 
scale  which  remain  above  the  surface  of  the  liquid. 
Tables  are  constructed,  so  that,  by  their  aid,  when  the 
number  on  the  scale  at  which  the  hydrometer  floats  in  a  given  liquid  is  de- 
termined by  experiment,  the  specific  gravity  is  expressed  by  figures  in  a  col- 
umn directly  opposite  that  number  in  the  table. 

The  liquid  whose  specific  gravity  is  to  be  determined,  is  usually,  for  conve- 
nience, placed  in  a  narrow  vessel  or  jar  (see  Fig.  9),  and  the  zero  point  on  the 
scale  of  the  hydrometer  is  always  placed  at  that  point  where  the  instrument 
will  float  in  pure  water.  The  numbers  on  the  scale  read  either  up  or  down, 
according  as  the  liquid  to  be  tested  is  either  heavier  or  lighter  than  water. 

For  the  testing  of  alcohol  and  spirituous  liquors,  a  particular  form  of  hy- 
drometer is  used,  called  the  "  alcoholo'meter."  This  is  so  graduated  as  to 
indicate  the  number  of  parts  of  pure  alcohol  in  a  hundred  of  liquid ; — perfectly 
pure,  or,  as  it  is  called,  "  absolute"  alcohol,  being  100,  and  pure  water  1. 

In  the  arts,  a  French  hydro'meter,  known  as  Beaume's,  and  an  English  in- 
strument known  as  Twaddell's,  so  called  from  their  makers,  are  much  used. 
Dealers  and  manufacturers  of  spirituous  liquors,  syrups,  oils,  leys  for  soap- 
making,  etc.,  in  buying,  selling,  or  compounding,  are  accustomed  to  indicate 
the  strength  or  quality  of  their  products,  by.  say  ing  that  they  stand  at  so  many 
degrees  Beaume,  or  TwaddelL 


.— What  is  a  hydrometer  ?  Upon  what  principle  may  the  specific  grarity 
of  a  liquid  be  determined  by  the  hydrometer  ?  How  is  the  hydrometer  graduated  ? 
What  is  an  alcoholometer  ?  What  are  the  instruments  known  as  Beaumo  and  Twad- 
dell? 


COHESION.  29 

The  practical  value  of  the  hydrometer  in  the  arts  as  a  labor-saving  inven- 
tion, is  very  great.  The  soap-maker,  by  dipping  the  instrument  into  his  ley, 
and  noticing  the  point  at  which  it  floats,  knows  at  once  by  experience  whether 
it  is  of  sufficient  strength  to  convert  his  grease  into  soap ;  the  salt-boiler,  by 
a  like  observation,  is  enabled  to  judge  how  long  his  brine  must  be  boiled  be- 
fore salt  will  deposit  at  the  bottom  of  his  kettles ;  and  the  bleacher  has  in  a 
like  manner  a  sure  check  against  the  use  of  bleaching  liquors  of  strength  suf- 
ficient to  damage  his  fabrics.  So  in  very  many  other  industrial  processes  also 
the  hydrometer  is  equally  useful. 

41.  Specific  Gravity  of  Gases, — In  principle,  the  method 
of  determining  the  specific  gravity  of  gases  is  the  same 
as  that  used  in  the  case  of  solids.  A  flask,  or  globe,  is 
first  weighed  empty,  then  when  filled  with  air,  and  a  third 
time,  when  the  gas  whose  specific  gravity  is  sought,  for, 
has  been  substituted  for  air.  The  difference  between  these 
respective  weights  furnishes  the  data  for  calculating  the 
specific  gravity  required. 

42.  The  specific  gravity  of  a  body  constitutes  one  of  its  most  important  and 
distinguishing  physical  characteristics.  Thus,  for  instance,  the  mineral  known 
as  iron  pyri'tes  resembles  gold  in  color  so  closely,  that  it  is  often  mistaken 
by  the  unskilled  for  that  metal.  It  may.  however,  be  at  once  distinguished 
from  gold  by  the  difference  in  specific  gravity,  an  equal  bulk  of  gold  being 
nearly  four  times  as  heavy. 

> 

SECTION    II. 

COHESION. 

43.  Cohesion  and  Chemical  Action, — The  force  with 
which  like  particles  of  matter  are  held  together  by  the  in- 
fluence of  cohesion,  or  what  is  termed  the  "  strength  of  ma- 
terials/' although  of  great  importance  in  all  the  operations 
of  the  mechanic,  the  engineer,  and  the  architect,  has  com- 
paratively little  to  do  with  Chemistry.  Variations,  how- 
ever, in  the  cohesion  and  aggregation  of  the  particles  of 
a  particular  substance,  modify,  to  a  considerable  extent,  the 
nature  and  rapidity  of  chemical  action  upon  it. 

Thus  gunpowder,  for  example,  when  hi  the  form  of  a  hard  cake,  or  as  fine 
dust,  burns  comparatively  slowly,  as  in  what  is  termed  a  slow  match,  or  fuse ; 

QUESTIONS.— Explain  the  practical  value  of  the  hydrometer  as  a  labor-saving  expedient. 
How  may  the  specific  gravity  of  a  gas  be  determined  ?  Is  the  specific  gravity  of  a  sub- 
stance one  of  its  important  characteristics  ?  What  is  the  relation  of  the  force  of  cohesion 
to  chemical  action  ? 


30  PRINCIPLES    OF     CHEMISTEY. 

but  in  the  form  of  fine  grains,  each  portion  quickly  ignites,  and  an  almost  in- 
stantaneous explosion  occurs. 

As  a  general  rule,  the  cohesion  of  a  body  diminishes  as 
its  temperature  increases.  A  heated  liquid  forms  smaller 
drops  than  a  cold  one.  Sulphur,  of  all  bodies,  is  an  ex- 
ception to  this  rule,  its  consistency  increasing,  after  melt- 
ing, as  its  temperature  rises. 

In  liquids,  notwithstanding  the  freedom  -with  which  their  particles  glide 
over  each  other,  there  still  exists  an  appreciable  amount  of  cohesion.  This  is 
shown  by  the  fact  that  every  detached  drop  of  a  liquid,  as  a  dew-drop  upon 
a  leaf;  always  assumes  a  rounded  form — a  globe  or  sphere  being  the  figure 
which  will  contain  the  greatest  amount  of  matter  within  a  given  surface. 

This  influence  of  cohesion  is  beautifully  shown  in  the  case  of  two  liquids 
which  do  not  mix  with  each  other,  but  which  have  precisely  the  same  specific 
gravity,  as  is  the  case  with  oil  and  alcohol  of  a  certain  degree  of  dilution. 
If  a  little  oil  be  poured  into  weak  alcohol,  it  remains  suspended  within  it  in 
the  form  of  a  perfect  spherical  mass.* 

44.  Limpid  and  Vis'cous  Liquids, — Liquids,  according  to 
the  difference  of  cohesive  force  which  exists  among  their 
particles,  have  received  the  distinctive  names  of  limpid 
and  vis'cous. 

Limpid  Liquids  are  those  which,  like  ether,  alcohol,  etc., 
display  great  mobility  of  their  particles.  Bubbles  pro- 
duced in  such  liquids  by  agitation,  quickly  rise  to  the  sur- 
face, break,  and  disappear. 

Vis'cous  Liquids  are  those  in  which  the  particles  are  held 
together  so  strongly,  by  the  force  of  cohesion,  that  they 
move  sluggishly  upon  one  another.  Oil,  syrup,  gum- 
water,  etc.,  are  examples  of  viscous  liquids. 


*  This  experiment  may  be  successfully  and  easily  performed  by  the  teacher  in  the  fol- 
lowing manner : — Oil  will  float  upon  the  surface  of  water,  but  will  sink  to  the  bottom  of 
strong  alcohol ;  if  we,  therefore,  pour  a  portion  of  alcohol  into  a  glass,  and  put  in  a  glo- 
bule of  oil  (olive  oil  is  preferable),  the  spirit  will  float  above  it,  and  the  oil  will  have  the 
form  of  a  flattened  spheroid.  If  we  now  add  a  little  water,  and  mix  it  carefully  with  the 
Bpirit  without  breaking  the  floating  mass  of  the  oil,  it  will  be  seen  to  swim  higher  up  in 
the  spirituous  medium  and  present  less  flatness,  and  by  continuing  to  carefully  add  water, 
we  may  at  last  bring  the  oil  to  the  very  center  of  the  fluid,  where  it  will  assume  the  form 
of  a  perfect  sphere. 

QUESTIONS. — What  relation  exists  between  cohesion  and  temperature  ?  Does  the  cohe- 
sive force  influence  the  particles  of  liquids  ?  Why  is  a  dew-drop  spherical  in  shape  ? 
What  experiment  illustrates  the  cohesion  of  liquids  ?  Into  what  two  classes  may  liquids 
be  divided  ?  What  is  a  limpid  liquid  ?  What  is  a  viscous  liquid  ? 


COHESION.  31 

45.  Variations  of  Cohesion  in  Solids,— Those  proper- 
ties of  solid  bodies  which  we  denominate  hardness,  soft- 
ness, brittlenesSy  malleability,  and  ductility,  are  occasioned 
by  variations  of  the  cohesive  force.     The  cause  of  these  va- 
riations, or  the  reason  why  one  metal  should  be  malleable 
and  another  ductile,  or  why  the  same  substances  should 
possess,  under  different  circumstances,  different  degrees  of 
hardness,  is  not  fully  understood. 

The  most  trifling  variations  in  the  external  circumstances  to  which  a  body 
is  subjected,  will  often  produce  the  most  extraordinary  differences  in  its  hard- 
ness, brittleness,  ductility,  and  malleability.  A  piece  of  steel  slowly  cooled 
from  a  red  heat  is  soft,  and  may  be  easily  cut  with  a  file,  or  stamped  with  a 
die ;  but  the  same  piece  of  steel,  if  heated  to  redness  and  suddenly  cooled, 
becomes  extremely  hard,  and  as  brittle  as  glass.  Gold  is  one  of  the  most 
ductile  of  metals,  but  if  a  mass  of  melted  gold  be  exposed  to  the  mere  fumes 
of  antimony,  it  loses  its  ductility  altogether.* 

46.  Hardness. — The  hardness  of  a  body  is  measured  by 
its  power  of  scratching  other  substances. 

The  variations  in  the  degree  of  hardness  presented  by 
different  bodies,  often  furnish  the  mineralogist  and  chem- 
ist with  a  valuable  physical  test,  by  which  they  are  en- 
abled to  distinguish  one  mineral  from  another.  For  «the 
purpose  of  facilitating  such  comparisons  a  table  has  been 
constructed,  by  taking  ten  well-known  minerals,  and  ar- 
ranging them  in  such  a  way  that  each  is  scratched  by  the 
one  that  follows  it.  Such  a  table  is  known  as  the  Scale 
of  Hardness  ;  and  by  comparing  any  unknown  mineral 
with  this  scale,  its  comparative  degree  of  hardness  may 
be  at  once  determined. 

For  example,  suppose  a  body  neither  to  scratch  nor  to  be  scratched  by 
pure  quartz,  or  rock  crystal,  which  is  No.  7  of  the  table,  its  hardness  is  said 
to  be  7 ;  if,  however,  it  should  scratch  quartz,  and  not  scratch  the  topaz, 
which  is  No.  8  of  the  table,  its  hardness  would  be  said  to  be  between  7  and 
8.  Very  many  different  minerals  have  the  same  external  appearance,  and  by 
the  sight  alone  can  not  be  distinguished  from  each  other ;  but  by  the  employ- 

*  See  Crystallization. 

QUESTIONS — What  physical  properties  of  bodies  are  due  to  variations  of  the  cohesive 
force?  How  is  the  hardness  of  a  body  measured  ?  What  is  the  scale  of  hardness? 
How  is  the  scale  of  hardness  used,  and  what  are  its  advantages  in  determining  the  char- 
acter of  minerals? 


32  PRINCIPLES     OF     CHEMISTKY. 

ment  of  this  test,  a  difference  in  their  physical  or  chemical  composition  inay 
be  at  once  recognized.* 

SECTION    III. 

ADHESION  AND  CAPIULAET  ATTRACTION. 

47.  Adhesion  and  Chemical  Actian, — The  force  of  ad- 
hesion is  exerted  between  substances  in  every  form  or 
condition.  When  it  occurs  between  solids,  it  is  the  prin- 
cipal cause  of  that  resistance  to  motion  which  is  termed 
friction. 

As  a  general  rule,  friction  is  greater  "between  surfaces 
of  the  same  substances  than  between  those  of  unlike  sub- 
stances. Thus  an  iron  axle  moving  in  an  iron  box  or 
socket,  experiences  a  greater  amount  of  friction  than  if 
revolving  in  a  brass  socket, 

"We  reduce  the  amount  of  friction  between  two  surfaces  by  interposing  some 
substances,  like  grease,  oil,  black-lead,  etc.,  the  particles-  of  whkh  have  very 
little  cohesion. 

The  valuable  properties  of  cements  and  mortars  depend 
entirely  upon  the  operation  of  the  force  of  adhesion.  The 
fact,  also,  that  different  kinds  of  cement  are  required  for 
joining  together  different  materials,  proves  that  adhesion 
acts  with  varying  degrees  offeree  between  different  kinds 
of  matter. 

Thus,  glue  or  gum  may  be  used  for  joining-  pieces  of  paper  or  wood;,  but 


*  The  following  is  the  scale  of  hardness  generally  adopted  : — 

1.  Talc.  6.  Feldspar, 

2.  Compact  gypsum.  T.  Limpid  quartz. 

3.  Calcareous  spar.  8.  Topaz. 

4.  Fluor  spar.  9,  Sapphire,  or  Cornndmn. 

5.  Apatite  (phosphate  of  lime).  10.  Diamond. 

Each  of  these  minerals  is  harder  than  those  which  precede  it,  and  is  softer  than  any 
•which  follow  it. 

Teachers  and  pupils  can,  with  the  exception  of  No.  10,  the  diamond,  easily  obtain  the 
materials  necessary  to  construct  the  scale  of  hardness  as  abore  given.     It  may  also  be  ob- 
tained, put  up  in  a  neat  box,  of  most  philosophical  instruments  dealer*,  at  a  trifling  ex- 
pense. 
. s ! 

QUESTIONS. — In  what  manner  is  the  force  of  adhesion  exerted?  What  is  friction? 
Under  what  circumstances  is  friction  the  greatest?  How  may  friction  be  diminished  ?  To 
what  are  the  valuable  properties  of  cements  and  mortar»  due?  What  facts  prove  the 
varying  force  of  adhesion? 


ADHESION   AND   CAPILLARY  ATTRACTION,      33 

they  will  not  answer  for  cementing  glass  or  china ;  while  for"  the  union  of 
marble,  brick,  or  stone,  a  cement  containing  lime  is  required* 

Generally,  the  force  of  adhesion  is  inferior  in  strength 
to  the  force  of  cohesion  :  Imt  in  some  instances  the  oppo- 
site is  true, 

Thus,  in  detaching  glue  from  the  surface  of  Wood,  it  hot  unfrequently  hap- 
pens that  portions  of  the  wood  are  torn  off  by  the  glue,  on  account  of  the 
force  of  adhesion  between  the  two  bodies  proving  stronger  than  the  force  of 
cohesion  between  the  particles  of  the  wood. 

The  property  of  water  to  adhere  to  solid  surfaces  and  wet  them,  and  the 
rapid  diffusion  of  a  drop  of  oil  over  the  surface  of  water,  are  illustrations  of 
the  force  of  adhesion  between  solids  arid  liquids,  and  between  different 
liquids. 

Some  experiments  seem  to  show  that  the  force  of  adhesion  may  even  over- 
come the  force  of  affinity  under  some  circumstances,  Thus,  when  vinegar" 
is  filtered  through  pure  quartz  sand,  the  first  portion  that 'rims  through  is  de- 
prived of  nearly  all  its  acid,  and  the  vinegar  will  not  pass  through  unchanged 
until  the  sand  had  become  charged  with  acid. 

48.  Surface  Action, — As  adhesion  takes  place  solely  be- 
tween the  surfaces  of  bodies,  it  is  evident  that  whatever 
circumstances  affect  surface  must  essentially  influence  the 
exertion  of  the  force  of  adhesion,  It  has  accordingly  been 
found  that  by  minutely  subdividing  a  body>  and  thus  in- 
creasing its  extent  of  surface,  we  generally  increase  the 
effect  of  adhesion. 

A  cubic  inch  of  matter  cut  into  little  cubes,  each  l-2400th  of  an  inch  on 
the  edge,  will  exhibit  a  surface  of  exactly  100  square  feet. 

All  pulverized  bodies,  by  reason  of  their  great  extent  of  surface,  attract 
moisture,  or  the-  vapor  of  water,  and  also  air,  so  that  by  exposure  to  the  at- 
mosphere they  increase  in  weight  to  a  considerable  extent. 

A  most  striking  illustration  of  the  faet  that  extent  of  surface  facilitates  the 
action  of  adhesion  is  found  in  the  case  of  charcoal.  When  wood  is  heated 
apart  from  the  air,  certain  portions  of  matter  which  compose  its  structure  are 
driven  off  by  the  action  of  the  heat,  and  the  charcoal,  which  remains  behind, 
is  left  full  of  little  pores,  or  openings.  In  this  way  an  enormous  extent  of 
surface  is  acquired,  so  much  so,  that  a  cubic  inch  of  good  charcoal  is  esti- 
mated to  have  a  surface  of  at  least  a  hundred  square  feet.  By  reason  of  such 
au  extended  surface,  the  effect  of  the  force  of  adhesion  existing  between  char- 


QUESTIONS— Why  is  not  glue  suitable  tor  cementing  glass  of  china  ?  Does  the  forqe  of 
adhesion  ever  prove  superior  to  the  force  of  cohesion  ?  What  are  illustrations  of  adhe- 
sion between  solids  and  liquids?  What  influence  has  surface  upon  adhesion?  Why  do 
most  pulverized  suhstances  attract  moisture  7  How  does  chaf  Soal  illustrate  the  influence 
of  surface  upon  the  force  of  adhesion  ? 


34  PRINCIPLES    OF     CHEMISTRY, 

coal  and  various  liquids  and  gases  is  greatly  increased.  Thus,  it  has  been 
found  that  freshly-burned  charcoal  is  capable,  through  the  force  of  adhesion, 
alone,  of  absorbing  or  condensing  upon  its  surface  from  80  to  90  times  its  own 
bulk  of  certain  gases ;  and  that  it  absorbs,  when  exposed  to  moist  air,  so  much 
Water,  as  to  increase  in  weight  by  nearly  one  fifth. 

All  coloring  matters  of  vegetable  or  animal  origin,  and  many  other  sub- 
Stances,  have  likewise  the  property  of  adhering  to  charcoal — a  circumstance 
which  has  been  turned  to  great  practical  advantage  in  the  arts. 

Other  substances  beside  charcoal,  exert,  by  reason  of  their  peculiar  ex- 
tension of  surface,  a  similar  influence  on  the  force  of  adhesion.  Metallic 
platinum,  finely  divided,  is  even  more  remarkable  in  its  effects  than  charcoal, 
and  is  capable  of  absorbing  eight  hundred  times  its  bulk  of  oxygen  gas. 
This  oxygen  must  be  contained  within  it  in  a  state  of  condensation  very 
like  that  of  a  liquid.  In  a  like  manner,  every  porous  body  attracts,  through 
the  force  of  adhesion,  air  and  moisture  to  a  greater  or  less  degree,  the  action 
of  the  force  being  proportioned  to  the  extent  of  the  porosity,  or  the  surface 
exposed.  A  field  whose  soil  is  finely  divided  and  kept  porous  by  a  high  state 
of  cultivation,  suffers  less  from  drought  than  one  similarly  situated  which  is 
partially  or  wholly  uncultivated.  It  is  not  improbable,  also,  that  plants  are 
assisted  in  obtaining  nutriment  from  the  air,  through  the  influence  of  an  ad- 
hesive force  acting  between  the  surfaces  of  their  leaves  and  the  constituents 
of  the  atmosphere. 

49.  Capillary  Attraction, — The  phenomena  produced  by 
the  agency  of  the  force  of  capillary  attraction  are  similar 
in  character  to  those  produced  by  the  force  of  adhesion. 
Indeed,  according  to  some  authorities,  capillary  attraction 
is  merely  a  variety  of  adhesion,*  The  fact,  however,  that 
capillary  attraction  both  elevates  and  depresses  the  sur- 
faces of  liquids,  seems  to  prove  that  there  are  essential 
differences  between  these  two  forces. 

The  two  distinguishing  manifestations  of  capillary  attraction  may  be  clearly 
illustrated  by  the  following  experiments : — 

If  a  liquid  be  poured  into  a  vessel,  as  water  in  glass,  whose  sides  are  of  such 
a  nature  as  to  be  wetted  by  it,  the  liquid  will  be  elevated  above  the  general 


*  According  to  the  latest  and  best  sustained  hypothesis  on  this  subject,  the  phenomena 
of  capillary  attraction  are  due  not  only  to  an  adhesive  attraction  between  the  liquid  and 
the  solid,  but  also  to  a  contractile  force  existing  on  the  free  surface  of  every  liquid,  and 
•which  is  increased  of  diminished  in  a  given  direction  by  the  convexity  or  concavity  of  this 
surface. 


QUESTIONS.— What  other  facts  illustrate  the  influence  of  surface  action  ?  Do  the  phe- 
nomena of  capillary  attraction  resemble  those  of  adhesion  ?  How  may  the  two  distin- 
guishing manifestations  of  capillary  force  be  exhibited  ? 


ADHESION   AND    CAPILLARY   ATTEACTION.      35 


FIG.  10. 


level  of  its  surface  at  the  points  where  it  touches  tho 
sides  of  the  vessel.     This  is  shown  in  Fig.  10. 

If,  however,  the  liquid  is  poured  into  a  vessel  whose 
sides  are  of  such  a  nature  that  they  are  not  wetted  by 
it,  as  in  the  case  of  quicksilver  in  glass  vessel,  then  tho 
liquid  will  be  depressed  below  the  general  level  of  its 
surface  at  the  points  where  it  comes  in  contact  with 
the  sides  of  the  vessel.  This  is  shown  in  Fig.  11. 


FIG.  11. 


In  like  manner,  if  we  plunge  a  small  tube  of  glass  into 
water,  the  liquid  will  rise  in  it  above  the  general  level ; 
but  if  we  plunge  it  into  mercury,  the  liquid  will  be  de- 
pressed below  the  general  level,  or  will  not  enter  the 
tube  at  all 

It  has  been  proved  by  experiment,  that  water,  through 
the  force  of  capillary  attraction,  can  be  made  to  pass 
through  a  crevice  the  width  of  which  is  less  than  one 
half  of  the  millionth  of  an  inch. 

Notwithstanding  the  force  which  capillary  attraction 
exerts  to  cause  liquids  to  rise,  or  pass  into  tubes  of  small 
diameter,  it  can  not  of  itself  establish  a  flowage,  or  con- 
tinuous current.  If,  however,  a  part  of  the  liquid  be  re- 
moved from  the  end  of  the  capillary  tube  by  evaporation, 
or  other  agency,  an  additional  portion  will  be  pushed  for- 
ward by  capillary  force  to  supply  its  place,  and  in  this 
way  a  current  may  be  established. 

An  illustration  of  this  is  seen  in  the  case  of  an  oil-lamp,  the  wick  of  which 
may  be  regarded  as  a  bundle  of  capillary  tubes.  So  long  as  the  lamp  remains 
unlighted,  the  wick,  although  full  of  oil  never  overflows;  but  when  the  lamp 
is  lighted,  and  the  oil  burned  off  from  the  top,  a  current  is  at  once  created. 

Different  liquids  do  not  appear  to  be  equally  suscept- 
ible to  the  action  of  the  capillary  force.  Thus,  if  we  rep- 
resent the  height  to  which  water  will  ascend  in  a  capillary 
tube  by  100,  the  height  to  which  alcohol  will  ascend  in  the 
same  tube  will  be  only  40,  and  a  solution  of  common  salt 
in  water,  88. 

50.  Filtration, — The  process  of  filtration,  or  the  separa- 
tion of  impurities  from  liquids  by  straining,  or  filtering 
them  through  some  porous  substance,  is  the  result  of  the 


QUESTIONS. — Can  capillary  force  produce'a  current  of  liquid  through  the  pores  of  a  sub- 
etanee  ?  Are  ail  liquids  elevated  to  the  same  height  in  capillary  tubes  ?  Upon  what  does 
the  nrocess  of  nitration  denend  ? 


36  PRINCIPLES     OF     CHEMISTRY. 

action  of  capillary  force.  The  pores,  or  interstices  which 
exist  between  the  particles  of  the  substance  used  as  a 
filter,  are  really  little  capillary  tubes  through  which  the 
liquid  passes,  leaving  the  solid  impurities  contained  in  it 
behind. 

When  a  drop  of  ink,  or  chocolate  falls  upon  cloth,  or  blotting-paper,  It  pro- 
duces a  dark  central  spot  surrounded  by  a  circle  of  a  paler  colored  liquid. 
This  is  due  to  the  fact  that  the  particles  of  the  liquid  only  are  enabled  to  dif- 
fuse themselves,  or  "spread,"  as  it  is  termed,  through  the  pores  of  the  ma- 
terial. That  appearance  of  the  skin  which  accompanies  a  contusion,  and  is 
termed  "  black  and  blue,"  is  a  similar  phenomenon — the  result  of  a  separation 
of  the  coloring  and  denser  matters  of  the  blood  from  the  watery  portions,  by 
a  process  of  filtration  through  the  pores  of  the  tissues. 

In  chemical  operations,  coarse  sand,  or  cloth,  is  sometimes  used  to  form 
filters,  but  most  generally  a  variety  of  porous,  or  unsized  paper  (blotting- 
paper),  is  employed.  Writing-paper  can  not  be  used  for  filtration,  as  its  pores 
are  filled  up  with  glue,  or  starch.  For  a  like  reason,  ink  does  not  "  spread" 
on  this  kind  of  paper. 

A  paper  filter  is  prepared  by  folding  a  circular  piece  of  unsized  paper  into 
the  form  of  a  quadrant,  which  is  then  opened  to  form  a  cone.  It  is  generally 
fitted  into  a  funnel,  which  is  supported  upon  a  stand.  (See  Fig.  12.) 

FiG.  12. 


A  filtered  liquid  is  termed  &  filtrate, 
51.  En'dosmo&is,—  When  two  liquids  which  are  capable 
of  mixing  with  each  other,  as  alcohol  and  water,,  are  sep- 


QUESTIONS. — Why  can  not  "  sized,'1  or  writing-paper,  be  used  for  filtration. I    How  is 
paper  filter  prepared  ?    What  is  a  filtrate  ?    What  is  endosmosia  2 


FIG.  13. 


ADHESION   AND   CAPILLARY   ATTRACTION.        37 

arated  by  a  substance,  or  partition  which  is  porous,  each 
will  pass  through  the  partition  in  opposite  directions,  in 
order  to  mix  with  the  other.  The  exchange,  however, 
always  takes  place  in  unequal  proportions,  so  that  the 
volume  of  one  liquid  increases  while  that  of  the  other 
diminishes.  This  phenomenon  is  known  by  the  name 
of  Endosmosis. 

The  name  Endosemose,  derived  from  the  Greek,  and  signifying  "to  go  in," 
is  applied  to  designate  the  stronger  current,  because  it  penetrates  into  the 
opposite  liquid  ;  while  the  name  Exosmose,  which  signifies  "to  go  out,"  is  ap- 
plied to  the  weaker  current. 

The  phenomena  of  endosmosis  may  be  illustrated  by  the  following'  ex- 
periments : — If  some  alcohol  be  placed  in  a 
bladder,  the  neck  of  which  is  tightly  tied, 
and  the  bladder  be  sunk  in  a  vessel  of 
Water,  the  water  will  pass  into  the  bladder 
to  such  an  extent  as  to  distend  it,  even  to 
bursting. 

The  same  result  may  be  also  shown  more 
effectively  by  means  of  an  instrument  called 
the  endogfflometer.  This  consists  (see  Fig. 
13)  of  a  bladder  filled  with  alcohol,  which 
is  tightly  fastened  to  one  end  of  a  tube  and 
inserted  in  a  vessel  of  water — the  tube  being 
sustained  in  a  vertical  position.  As  the 
water  introduces  itself  through  the  pores 
of  the  bladder  the  liquid  rises  in  the  glass 
tube,  andr  if  the  action  be  continued  suffi- 
ciently long,,  it  wfll  rise  to  the  top  and  over- 
flaw.  Such  an  instrument  as  this  may  be 
kept  in  operation,  a  long  time,  the  liquid 
flowing  continually  over  the  top  of  the  tube. 
At  the  same  time  that  the  water  is-  passing; 
from  without  into-  the  bladder  to  reach  the 
alcoholr  a  very  small  quantity  of  alcohol  is 
PI  passing  through  the  bladder  in  a  contrary 


direction  to  reach  the  water. 


The  explanation  of  this  phenomenon  of  endosmosis  is  as  follows  r — The 
pores  of  the  bladder,  or  any  other  'like  substance,  are  merely  short  capillary 
tubes  through  which  the  water  passes-  by  the  force  of  capillary  attraction. 
If  the  bladder  be  distended  with  air  and  sunk  nnder  water,  the  water  will  fill 
the  tubes,  but  wiB  not  discharge  itself  in  the  interior,  since  capillary  force 


QtnEBTiONS. — What  is  the  origin  and  derivation  of  the  name  ?    What  experiments  illus- 
trate the  phenomena  of  endosmosis  2    How  is  endosmosis  explained  2 


38  PRINCIPLES     OF     CHEMISTRY. 

alone  can  not  establish  a  continuous  movement.  But  when  the  bladder  is 
filled  with  alcohol,  the  case  is  different ;  since  the  alcohol  dissolves  away  the 
water  as  fast  as  it  reaches  th'e  interior,  and,  thus  produces  a  constant  and  rapid 
current. 

The  reason  that  the  water  passes  in  more  rapidly  than  the  alcohol  passes 
out,  is  due  to  the  fact  that  the  water  adheres  more  strongly  to  the  walls  of 
the  bladder  than  the  alcohol  does— and  of  any  two  liquids,  that  which  most 
freely  wets  the  porous  dividing  partition  will  always  flow  in  the  stronger 
current 

Any  two  liquids  may  be  used  to  exhibit  the  action  of  endosmosis,  provided 
that  they  have  different  degrees  of  attraction  for  the  bladder,  and  a  strong 
tendency  to  mix  with  each  other.  Thus,  in  the  above  experiment  a  solution 
of  gum,  of  salt,  or  of  sugar  in  water,  might  have  been  substituted  in  place  of 
the  alcohol. 

Yery  thin  plates  of  slate-stone,  or  of  baked  clay,  may  be  also  used  in  place 
of  a  bladder,  or  membrane. 

The  force  with  which  a  liquid  will  pass  through  a  pore 
to  mingle  with  another  liquid  beyond  is  very  great — oc- 
curring in  some  instances  in  opposition  to  a  pressure  of 
from  forty  to  seventy  pounds  upon  a  square  inch. 

An  India-rubber  bottle,  filled  with  sulphuric  ether,  and  carefully  closed, 
will  gradually  empty  itself  if  placed  in  either  alcohol  or  water.  If  filled  with 
alcohol,  it  distends  itself  in  ether,  but  empties  itself  in  water ;  if  filled  with 
water,  it  distends  when  placed  in  either  alcohol  or  ether. 

If  a  bladder  containing  equal  parts  of  alcohol  and  water  be  hung  up  in  the 
air,  the  water  will  gradually  escape  through  the  membrane,  leaving  the  strong 
spirit  behind.  In  the  same  manner,  if  strong  alcohol  be  placed  in  a  wine- 
glass covered  with  porous  paper,  the  water  contained  in  it  escapes,  and  the 
spirit  increases  in  strength. 

Endosmotic  action  exercises  an  important  influence  in 
many  of  the  operations  of  chemistry,  and  of  animal  and 
vegetable  life. 

The  power  which  plants  possess  of  absorbing  nutritive  matter  from  the 
soil,  through  the  delicate  fibers  of  their  roots,  is  supposed  to  bo  due  in  part 
to  the  action  of  endosmosis. 

All  nutriment  taken  up  by  the  organs  of  the  body,  reaches  the  interior  of 
the  system  by  passing  through  animal  membranes  in  the  fluid  state.  The 
food  we  eat  passes  from  the  mouth  through  the  throat  to  the  stomach.  The 
structure  of  the  membranes  which  line  the  throat  is  such,  that  fluids  can  not 
pass  through  them,  but  the  walls  of  the  stomach  and  of  the  intestines  are 

QUESTIONS. — What  determines  the  rapidity  of  the  two  currents  in  endosmotic  action? 
Under  what  circumstances  will  different  liquids  exert  this  action  ?  Does  endosmosis 
exert  an  influence  upon  chemical  and  physiological  operations  ?  What  are  illustrations 
of  this  fact  ? 


ADHESION   AND   CAPILLARY   ATTRACTION.        39 


FIG.  14. 


§  a 


differently  constituted,  and  at  these  points  endosmotic  action  is  continually 
and  energetically  going  on  within  us. 

Endosmotic  action  takes  place  between  different  gases 
much  more  powerfully  than  between  different  liquids.  No 
matter  what  the  thickness,  or  thinness  of  the  porous  sub- 
stance separating  two  gases  may  be,  currents  are  estab- 
lished through  it,  until  the  media  on  both  sides  have  the 
same  chemical  composition. 

The  following  simple  experiment  shows  this  action : — If  we  tie  over  the 
mouth  of  a  glass  jar  filled  with  carbonic  acid  gas,  a  thin  sheet  of  India  rubber, 
and  expose  the  whole  to  the  air,  the  car- 
bonic acid  will  pass  out  so  fast  that  the 
cover  will  be  depressed  by  the  external 
pressure  of  the  atmosphere  almost  to  the 
bottom  of  the  jar.  (See  a,  Fig.  14.)  If, 
on  the  contrary,  we  fill  the  jar  with  air, 
and  place  it  in  an  atmosphere  of  carbonic 
acid,  the  movement  takes  place  in  an 
opposite  direction— a  little  air  flows  out 
of  the  bottle  into  the  carbonic  acid,  but  so 
large  a  quantity  of  the  gas  .passes  the 
opposite  way,  that  the  India  rubber  swells 
out,  and  caps  the  bottle  like  a  dome.  (See 
6,  Fig.  14.) 

52.  Diffusion  of  Gases,— Connected  with  this  subject 
is  another  interesting  class  of  phenomena,  known  as  the 
diffusion  of  gases. 

When  two  liquids  which  are  wanting  in  any  attraction 
for  each  other,  as  oil  and  water,  are  mixed  together,  they 
separate  after  standing  at  rest,  and  arrange  themselves 
according  to  their  specific  gravities,  the  heaviest  at  the 
bottom  and  the  lightest  at  the  top.  If,  however,  a 
light  and  heavy  gas  are  once  mixed  together,  no  sepa- 
ration takes  place,  but  the  two  remain  permanently  in- 
termingled. 

It  has  also  been  found  that  every  gas,  or  gaseous  mix- 
ture, possesses  the  power  of  diffusing  itself  equally 


QUESTIONS.— Does  endosmotic  action  take  place  between  different  gases  ?  What  are 
illustrations  of  it  ?  What  is  meant  by  the  diffusion  of  gases  ?  How  is  each  gas  affected 
as  regards  the  presence  of  another  gas  ? 


40 


PKINCIPLES  OF  CHEMISTRY. 


through  every  other  gas  with  which  it  is  brought  in  con- 
tact, and  this,  too,  in  opposition  to  the  action  of  their 
weight,  or  gravity. 

PIG  15  Tims>  carbol"c  aci^  gas  is  twenty-two  timea  heavier  than 

hydrogen  gas,  but  if  a  jar  filled  with  hydrogen  be  placed  with 
its  mouth  downward  over  the  mouth  of  a  jar  filled  with  car- 
bonic acid,  as  shown  iu  Fig,  15,  the  two  will  diffuse  them- 
selves so  completely  that  in  a  few  moments  each  jar  will  con- 
tain equal  quantities  of  both  gases, 

Each  gas  appears  to  act  as  void,  or 
empty  space  for  another,  or,  in  other  words, 
it  spreads,  or  expands  into  the  space  occu- 
pied by  another  gas,  as  if  it  were  a  vacuum. 
The  same  law  applies  also  to  vapors. 

Thus,  as  much  steam  can  be  forced  into  a  space  filled  with 
dry  air,  as  into  a  space  absolutely  devoid  of  air,  or  any  other* 
substance. 

This  force,  or  law,  regulating  the  diffusion  of  gases,  is  one 
of  great  practical  importance  in  the  operations  of  nature,  and 
is  often  referred  to  aa  a  most  remarkable  evidence  of  design 
on  the  part  of  the  Creator.  Thus,  carbonic  acid,  which  is  a 
deadly  poison  when  inhaled,  is  one  and  a  half  times  heavier  than  common 
air.  The  atmosphere  contains  about  one  part  in  two  thousand  of  this  gas, 
uniformly  diffused  through  it — the  same  quantity  being  present  in  air  col- 
lected on  the  tops  of  the  highest  mountains  and  on  the  level  surface  of  the 
earth.  If  the  law  which  produces  such  a  complete  diffusion  were  suspended, 
this  heavy  gas  would  accumulate  under  the  influence  of  gravitation  as  a  bed 
or  layer  in  the  lower  part  of  the  atmosphere,  and  render  the  immediate  sur- 
face of  the  earth  uninhabitable. 

By  reason  of  this  same  law  of  diffusion,  the  carbonic  acid  gas  which  is 
abundantly  formed  in  every  process  of  combustion  and  in  respiration,  and  the 
noxious  gases  discharged  from  sewers,  and  from  all  decaying  matter,  are  si- 
lently and  speedily  dispersed,  and  prevented  from  accumulating, 

The  equable  diffusion  of  vapor  of  water  through  the  atmosphere,  in  ac- 
cordance with  the  same  law,  is  no  less  important  than  the  diffusion  of  gases. 
But  for  such  diffusion,  the  whole  surface  of  the  earth  would  have  assumed 
the  condition  of  an  arid  desert.  Water  is  800  times  more  dense  than  air,  yet 
the  particles  of  water  in  the  form  of  vapor  ascend  into  the  atmosphere,  and 
diffusing  themselves  everywhere  throughout  its  substance,  give  rise  to  the 
phenomena  of  dew  and  rain. 

It  is  through  the  operation  of  this  principle,  also,  that  we  arc  enabled  to 

QUESTIONS.— What  practical  bearing  has  the  law  of  diffusion  upon  the  constitution  of 
the  atmosphere  ?  What  upon  the  condition  of  the  earth's  surface  ?  How  is  it  that  ire 
are  enabled  to  perceive  the  odor  of  volatile  substances  at  a  distance  ? 


ADHESION   AND   CAPILLARY   ATTRACTION.       41 

perceive  and  enjoy  at  a  distance  the  fragrant  odors  which  arise  from  volatile 
substances ;  and  were  its  action  suspended,  the  sense  of  smell  would  be  nearly 
unknown  to  us. 

53.  Diffusion  of  Liquids —Liquids  of  different  densities, 
which  are  susceptible   of  mixing,  will,  when  brought  in 
contact,  gradually  become  intermingled,  by  a  law  some- 
what resembling  that  which  governs  the  diffusion  of  gases. 

Thus,  if  pure  water  be  carefully  poured  upon  a  strong*  solution  of  salt  or  of 
sugar,  the  lighter  fluid  will  at  first  float  upon  the  surface  Of  the  heavier ;  but 
after  a  time  the  two  will  mingle  together  more  or  less  uniformly.  In  like 
manner,  a  drop  of  ink,  or  other  similar  coloring  matter,  will  diffuse  itself 
through  a  large  quantity  of  water. 

54.  Solution, — When  the  adhesion  between  the  parti- 
cles of  a  solid  and  those  of  a  fluid  is  more  powerful  than 
the  force  of  cohesion  which  binds  together  the  particles  of 
the  solid,  the  power  of  cohesion  will  be  entirely  overcome, 
or  suspended,  and  the  substance  is  said  to  dissolve,  or 
undergo  solution  in  the  liquid.     In  this  way  sugar  or  salt 
dissolves  in  water,  rosin  or  camphor  in  alcohol,  and  lead 
or  silver  in  mercury. 

A  body  is  said  to  be  insoluble  when  the  adhesive  force 
exerted  by  a  liquid  upon  its  particles,  is  not  strong 
enough  to  overcome  the  cohesive  force  which  binds  them 
together. 

Any  thing  which  weakens  the  force  of  cohesion  in  a  solid  favors  solution. 
Thus,  if  a  substance  be  reduced  to  a  powder,  it  dissolves  more  quickly,  both 
from  the  larger  extent  of  surface  which  it  exposes  to  the  action  of  the  liquid, 
and  from  the  partial  destruction  of  cohesion  between  its  particles.  In  the 
same  way  heat,  by  diminishing  the  force  of  cohesion,  generally  promotes  the 
process  of  solution.  Some  substances,  however,  as  lime,  for  example,  dis- 
solve more  freely  in  cold  than  in  warm  water. 

55.  Saturation, — When  a  liquid  has  dissolved  as  much 
of  a  solid  as  it  is  capable  of  doing,  it  is  said  to  be  satu- 
rated.    When  this  occurs,  the  force  of  adhesion  between 
the  liquid  and  the  solid  becomes  reduced  to  an  equality 
with  the  force  of  cohesion  between  the  particles  of  the 
solid,  and  the  act  of  solution  ceases. 

QTTESTIOXS. — What  is  understood  by  the  diffusion  of  liquids  ?  What  are  illustrations  of 
liquid  diffusion  ?  What  is  solution  ?  When  is  a.  body  said  to  be  insoluble  ?  What  cir- 
cumstances fayor  the  solution  of  a  solid  ?  What  is  saturation  ? 


42  PRINCIPLES    OF     CHEMISTRY. 

56.  Precipitation, — When  a  solid  body  dissolves  in  a 
liquid,  the  property  of  cohesion  is  not  destroyed,  but 
merely  overcome,  or  suspended  by  the  superior  force  of 
adhesion.  If  this  latter  force  is  in  turn  weakened,  or 
overcome,  the  force  of  cohesion  acquires  an  ascendancy, 
and  the  particles  in  solution  unite  again  to  form  a  solid. 
A  solid  thus  reproduced  and  separated  from  a  liquid,  is 
called  a  Precipitate. 

Thus,  the  common  solution  of  camphor  is  formed  by  dissolving  the  camphor 
gum  in  alcohol  If  water  be  added  to  this  solution,  the  alcohol  at  once  mixes 
with  the  water,  and  abandons  the  camphor,  which  immediately  resumes  its 
solid  form,  and  falls  to  the  bottom  of  the  vessel — it  is  precipitated. 

The  precipitation  of  a  solid  from  its  solution  may  also  be  effected  by  several 
other  methods : — 

Especially  may  this  be  accomplished  by  changing  the  character  of  the  sub- 
stance held  in  solution,  by  bringing  in  contact  with  it  another  body  with  which 
it  is  able  to  unite  chemically,  and  form  an  insoluble  compound.  Thus,  lime 
is  somewhat  soluble  in  water,  but  if  we  bring  carbonic  acid  gas  in  contact 
with  it  while  in  solution,  the  two  substances  unite  together  by  the  action 
of  the  chemical  force  of  affinity,  and  overcome  the  adhesion  which  the  water 
previously  had  for  the  lime.  The  compound  of  carbonic  acid  and  lime  thus 
produced,  being  solid  and  insoluble,  is  immediately  precipitated. 

The  above  case  illustrates  a  general  law  in  chemistry,  which  may  be  stated 
as  follows : — 

Two  substances  which,  when  united,  form  an  insoluble 
compound,  generally  combine  and  produce  the  same  com- 
pound when  they  meet  in  solution. 

This  law  is  practically  taken  advantage  of  in  chemical  operations  for  sepa- 
rating the  different  constituents  of  a  compound  from  each  other,  or  for  detect- 
ing the  presence  of  a  body  when  in  solution  with  other  substances.  Thus,  if 
it  is  desirable  to  know  whether  a  perfectly  clear  spring-water  contains  lime, 
carbonic  acid  gas  is  introduced  into  it.  This  uniting  immediately  with  the 
lime,  forms  an  insoluble  compound,  which  is  precipitated.  On  the  other  hand, 
by  reversing  the  process  and  introducing  a  solution  of  lime,  we  may  be  able 
to  detect  the  presence  of  carbonic  acid  under  the  same  circumstances. 

The  depression  of  the  temperature  of  a  solution  will  sometimes  cause  the 
cohesion  of  the  particles  of  the  solid  dissolved  to  acquire  an  ascendancy  over 
the  force  of  adhesion.  Thus,  alum  dissolved  in  hot  water  will  resume  in  part 


QUESTIONS — What  is  a  precipitate  ?  Give  an  illustration.  How  may  precipitation  be 
effected  by  changing  the  character  of  a  substance  ?  What  ireneral  law  governs  the  precipi- 
tation of  substances  from  their  solutions  ?  How  is  this  law  practically  applied  in  chemical 
operations  ?  How  may  precipitation  be  effected  through  a  depression  of  the  temperature 
of  a  solution  ? 


ADHESION   AND   CAPILLARY   ATTRACTION.      43 

its  solid  form  as  the  solution  is  cooled ;  and  when  brandy  is  exposed  to  in- 
tense cold,  many  degrees  below  that  necessary  to  freeze  water,  the  spirit- 
uous portion  retains  its  liquid  form,  and  separates  from  the  aqueous  part, 
which  solidifies  as  ice. 

A  remarkable  illustration  of  this  action  is  to  be  found  in  the  fact  that 
ice  formed  by  the  freezing  of  sea- water  is,  under  all  ordinary  circumstances, 
fresh,  and  entirely  destitute  of  salt.  The  great  ice-fields  which  cover  the 
ocean  in  the  Arctic  and  Antarctic  regions,  are  always  composed  of  fresh- water 
ice.  Indeed,  water  in  the  act  of  freezing  separates  completely  from  every 
thing  which  it  previously  held  in  solution.  Even  the  air. contained  in  water 
is  expelled  in  the  act  of  freezing,  and  becoming  entangled  in  the  thickening 
fluid,  gives  rise  to  the  minute  bubbles  generally  observed  in  blocks  of  ice. 
For  a  like  reason,  the  ice  formed  by  the  congelation  of  a  solution  of  indigo 
is  colorless. 

Elevation  of  temperature  will  also  effect  the  separation  of  bodies  in  solution. 

"When,  for  instance,  a  solution  of  common  salt  in  water  is  exposed  to  the 
action  of  heat,  the  repulsive  power  of  this  agent  overcomes  not  only  the 
cohesion  of  the  water,  but  also  its  adhesion  to  the  salt ;  the  water  assumes 
the  triform  state,  and  passes  off  as  steam,  while  the  salt,  deprived  of  its 
solvent,  resumes  the  solid  state. 

57.  Solution  and  Chemical  Combination, — A  clear  dis- 
tinction exists  between  a  solution  and  a  chemical  combi- 
nation, which  latter,  in  ordinary  language,  is  often  termed 
a  solution. 

A  simple  solution  is  occasioned  by  the  action  of  the 
force  of  adhesion  exerted  between  the  particles  of  the  solid 
and  the  liquid  with  which  it  is  brought  in  contact.  In  all 
cases  of  simple  solution,  the  properties  of  both  the  solid 
and  the  liquid  are  retained. 

Thus  sugar,  whether  in  a  mass  in  the  hand,  or  dissolved  in  water,  is  the 
same  substance ;  so  also  when  camphor  is  dissolved  in  alcohol,  the  solution 
partakes  of  the  properties  of  both,  having  the  smell  and  taste  of  both  cam- 
phor and  spirit. 

When  a  solid  disappears  in  a  liquid  through  the  influ- 
ence of  a  chemical  force  exerted  between  the  particles  of 
the  two  substances,  the  compound  is  not  a  true  solution, 
but  a  chemical  combination,  in  which  the  properties  of 
both  the  solid  and  liquid  are  essentially  changed. 


QXTESTTONS.— What  are  illustrations  of  this  principle  ?  Why  is  ice,  formed  by  the  freez- 
ing of  sea-water,  fresh  ?  What  is  the  occasion  of  the  numerous  bubbles  observed  in 
blocks  of  ice  ?  How  may  precipitation  be  effected  by  an  elevation  of  temperature?  State 
and  illustrate  the  difference  between  solution  and  chemical  combination. 


44  PRINCIPLES     OF     CHEMISTRY. 

Thus,  iron  placed  in  diluted  acid  disappears  in  it,  but  the  resulting  liquid 
does  not  contain  finely  divided  iron,  but  a  finely  divided  compound  of  iroti 
and  the  acid,  which  possesses  entirely  different  properties  from  either  of  its 
constituents. 

Solution  differs  also  from  chemical  combination  in  the  varying  proportions 
in  which  it  occurs,  according  to  temperature,  etc.  Thus,  a  given  quantity  of 
water  at  the  boiling  temperature  will  dissolve  nearly  four  hundred  times  more 
saltpetre  than  it  can  at  a  temperature  of  60°  ;  but  in  chemical  combinations 
the  proportions  in  which  bodies  unite  are  fixed  and  invariable. 

SECTION    IT. 

CRYSTALLIZATION. 

58.  Crystals, — The  particles  of  most  substances,  in  pass- 
ing from  a  liquid  to  a  solid  condition,  have  a  tendency  to 
arrange  themselves  into  regular  and  symmetrical  forms, 
each  different  substance  assuming  always  a  peculiar  shape, 
from  which  it  never  essentially  varies.     Such  regular  geo- 
metrical solids  are  termed  Crystals. 

The  number  of  known  crystalline  forms  is  much  smaller  than  the  num- 
ber of  substances  which  are  capable  of  crystallizing,  and"  it  therefore  follows 
that  crystals  of  various  kinds  of  matter  may  possess  the  same  form.  Xo 
substance,  however,  has  ever  been  found  to  be  capable  of  assuming  indiffer- 
ently any  form,  but  most  substances  are  restricted  to  one  form  of  crystal 
and  its  modifications.  This  circumstance  enables  us,  very  often,  to  identify 
a  substance,  or  determine  its  composition,  simply  by  the  shape  of  its  crystals. 
For  example,  common  salt  always  crystallizes  in  cubes,  alum  in  octohedrons, 
saltpeter  in  six-sided  prisms,  Epsom  salts  in  four-sided  prisms,  and  so  on. 

59.  Amor 'phous  Bodies,— A  solid  whose  particles  are  ar- 
ranged irregularly,  and  which  possesses  no  definite  exter- 
nal form,  is  said  to  be  amorphous  (i.  e.,  without  form). 

Every  solid  body  is  either  amorphous,  or  crystalline,  and  many  bodies  exist 
in  both  of  these  conditions.  Thus,  carbon,  in  the  form  of  charcoal  and  lamp- 
black, is  amorphous,  but  in  the  form  of  the  diamond  it  is  crystalline. 

60.  Formation  of  Crystals, — The  usual  method  of  ob- 
taining crystals  is  to  form  a  strong  solution  of  the  sub- 
stance in  hot  water,  as  -most  bodies  dissolve  more  freely  in 
water  when  it  is  at  an  elevated  temperature  than  when 

QTTESTIONS. — What  are  crystals  ?  Can  a  substance  in  crystallizing  assume  indifferently 
any  form  ?  What  are  amorphous  bodies  ?  Can  a  substance  be  both  crystalline  and  amor- 
phous ?  What  is  the  usual  method  of  obtaining  crystals  ? 


CRYSTALLIZATION. 


45 


cold.  As  the  liquid  cools,  and  the  force  of  cohesion  gra- 
dually begins  to  resume  the  ascendancy,  the  separated 
particles  of  the  solid  have  time  to  select,  as  it  were,  the 
arrangement  they  will  assume,  and  crystals  are  formed. 

When  a  solid  is  melted,  or  made  to  assume  a  liquid 
form  by  heating,  and  allowed  to  cool  quietly,  its  particles 
also,  in  most  instances,  assume  a  crystalline  arrangement. 

Illustrations  of  this  may  be  seen  in  the  crystalline  fracture  of  zinc  and 
antimony.  Sulphur,  also,  crystallizes  beautifully  on  cooling  after  fusion. 

"Water,  in  freezing,  or  assuming  the  solid  condition,  often  shoots  into  beau- 
tiful crystals,  as  may  be  seen  by  examicing  the  snow-flakes  which  fall  dur- 
ing a  period  of  intense  cold,  beneath  a  microscope.  These  crystals  may 
also,  under  favorable  circumstances,  be  seen  with  the  naked  eye,  by  placing 
the  flake  upon  a  dark  body  cooled  below  32°  F.  Fig.  16  represents  some  of 
the  varied  and  beautiful  forms  of  snow  crystals. 

FIG.  16. 


The  same  crystals  which  appear  in  snow,  exist  also  in  ice,  but  they  are 
so  blended  together  that  their  symmetry  is  lost  in  the  compact  mass.  "When 
"water  freezes,  its  particles  all  arrange  themselves  in  ranks  and  lines  which 
cross  each  other  at  angles  of  60  and  120  degrees.  This  may  be  seen  by 
examining  the  surface  of  water  in  a  saucer  while  freezing. 

If  we  fracture  thin  ice,  by  allowing  a  pole,  or  weight  to  fall  upon  it,  the, 
fracture  will  have  more,  or  less  of  regularity,,  being  generally  in  the  form  of 
a  star,  with  six  equidistant  radii,  or  angles  of  60°. 

Another  beautiful  illustration  of  the  crystallization  of  water  in  freezing,  is 
seen  in  the  frost-work  upon  windows  in  winter,  caused  by  the  congelation 

QUESTIONS.— What  peculiarities  of  crystallization  does  water  present  in  freezing?  Has 
ice  a  crystalline  structure  ?  What  occasions  the  symmetrical  arrangement  of  frost-work 
upon  windows,  etc.,  in  winter? 


46  PRINCIPLES     OF     CHEMISTRY. 

of  the  vapor  of  the  room  when  it  comes  in  contact  with  the  cold  surface  of 
the  glass.  All  these  frost-work  figures  are  limited  by  the  laws  of  crystalli- 
zation, and  the  lines  which  bound  them,  form  among  themselves  no  angles 
but  those  of  30°,  60°,  and  120°. 

When  a  substance  has  been  converted,  through  the  ac- 
tion of  heat,  into  a  vapor  or  gas,  and  then  by  cooling  is 
caused  to  change  back  again  at  once  into  the  solid  state, 
its  particles  arrange  themselves  so  as  to  form  crystals. 

Thus,  camphor,  or  sulphur,  if  heated  in  a  glass  tube,  will  be  first  con- 
verted into  vapor,  and  then  deposited  in  a  ring  of  crystals  higher  up,  at  the 
first  point  where  the  temperature  is  sufficiently  low. 

In  general,  it  is  important  to  the  process  of  crystalliza- 
tion that  the  liquid  from  which  the  solid  body  is  separating 
should  not  be  shaken  or  disturbed,  but  when  the  forces 
of  cohesion  and  adhesion  aro  nearly  balanced,  as  in  a  sat- 
urated solution,  it  seems  necessary  that  some  slight  mo- 
tion should  be  given  to  the  liquid  in  order  to  initiate  the 
process,  which  does  not  commence  at  all  in  a  state  of 
absolute  rest. 

Thus,  a  saturated  hot  solution  of  Glauber's  salt,  if  allowed  to  cool  in  per- 
fect stillness,  will  remain  liquid  as  long  as  the  stillness  is  preserved,  but 
the  slightest  movement  or  tremor — even  a  wave  of  the  hand  through  the 
air  in  its  vicinity — will  instantly  transform  the  solution  into  a  solid  mass, 
some  of  the  water  entering  into  the  composition  of  the  crystals,  and  some 
being  retained  by  interstices  in  their  structure.  In  the  same  manner,  water- 
may  be  cooled  eight,  or  ten  degrees  below  the  freezing  point  and  yet  remain 
liquid;  but  the  slightest  disturbance,  even  a  vibration  of  the  vessel,  will 
cause  it  to  freeze  (crystallize)  instantaneously. 

The  more  slowly  a  liquefied  body  is  brought  back  to  a 
solid  state,  and  the  more  the  liquid  is  kept  at  rest  after 
the  process  of  crystallization  has  commenced,  the  smaller 
will  be  the  number  and  the  larger  the  sizevof  the  crystals 
produced  ;  but  when  the  solution  is  caused  to  solidity  very 
quickly,  the  crystals  are  numerous,  but  small  and  imper- 
fect. 

In  the  first  case  the  particles"  of  the  solidifying  body  have  time  to  arrange 
themselves  regularly  upon  each  other  ,•  but  in  the  latter  instance  the  solidifi- 


QUESTIONS. — Under  what  other  circumstances  may  crystallization  take  place  ?  What 
are  important  requisites  in  the  process  of  crystallization  ?  What  facts  illustrate  these  con- 
ditions ?  Under  what  circumstances  will  crystals  be  perfect,  and  when  imperfect  ? 


CRYSTALLIZATION.  47 

cation  takes  place  so  rapidly  that  the  particles  attach  themselves  irregularly, 
and  interlace  with  each  other  in  every  direction.  In  this  consists  the  differ- 
ence between  "sugar,"  or  "rock  candy"  and  loaf,  or  granulated  sugar;  be- 
tween the  fine  grained  statuary  marble  and  crystallized  "  spar." 

Crystals  have  always  a  tendency  to  fasten  upon  any 
foreign  substance  that  occupies  a  prominent  position  in 
the  liquid  which  affords  them,  a  circumstance  which  is 
applied  to  many  useful  purposes  in  the  arts. 

Illustrations  of  this  are  seen  in  the  formation  of  the  somewhat  familiar  or- 
nament known  as  the  "  alum  basket,"  and  in  the  strings  which  are  stretched 
across  the  vessels  in  which  pure  solutions  of  sugar  crystallize  in  the  manu- 
facture of  ' '  rock  candy. "  When  only  two  or  three  very  minute  crystals  can  be 
deposited,  it  is  usual  to  place  a  piece  of  thread  or  some  other  suitable  sub- 
stance in  the  liquor ;  and  upon  this  support  the  crystals,  if  anywhere,  will  be 
found.  In  this  way  the  chemist  is  enabled  to  draw  together  and  collect 
readily  the  smallest  quantities  that  can  be  thrown  down  from  a  solution. 

Nothing  can  be  more  beautiful  than  to  watch  the  progress  of  crystallization 
as  it  takes  place  when  we  suspend  a  series,  or  network  of  threads  in  a  hot 
saturated  solution  of  alum,  and  then  allow  the  liquor  to  cool  slowly.  Tho 
minute  invisible  atoms  are  gradually  drawn  together  toward  the  foundation 
thus  afforded,  and  presently  little  glittering  specks  may  be  discerned  entan- 
gled among  the  fibers,  or  studding  the  network  of  the  threads.  If  the  pro- 
cess be  well  managed,  these  specks  increase  steadily  in  size,  by  the  regular 
addition  of  fresh  atoms  to  every  part ;  but  if  the  temperature  be  not  attended 
to,  or  the  solution  be  improperly  disturbed,  they  increase  chiefly  in  numbers, 
and  the  larger  crystals  are  apt  to  bo  disfigured  by  adhering  to  small  ones.* 

61.  Purification  by  Crystallization, — A  substance  in 
crystallizing  has  a  tendency  to  purify,  or  separate  itself 
from  any  foreign  substances  which  may  have  been  mingled 
with  it.  Crystalline  form  is,  therefore,  to  some  extent,  a 


*  "  The  beautiful  crystalline  masses  that  are  sometimes  seen  in  druggists'  windows, 
can  not  be  produced  without  the  greatest  care  and  attention,  each  crystal  being  separated 
from  the  liquor  when  it  has  attained  a  sufficient  size,  and  being  placed  alone  in  a  shallow- 
pan,  perfectly  glazed,  at  a  temperature  carefully  regulated,  and  under  a  solution  of  a 
specified  strength.  It  is  then  turned  over  from  day  to  day,  as  otherwise  the  face  in  con- 
tact with  the  pan  would  be  prevented  from  increasing,  and  a  deformed  crystal  would  re- 
sult. It  is  also  carefully  supplied  with  fresh  solution  from  time  to  time  :  because,  if  that 
around  it  were  exhausted,  its  most  prominent  angles  would  be  re-dissolved.  By  neglect- 
ing these  precautions,  deformed  or  monstrous  crystals  are  obtained,  and  are  exhibited, 
perhaps,  as  often  as  the  perfect  ones.  Crystalline  masses  of  the  blue  sulphate  of  copper, 
the  red  chromate  of  potash,  of  alum,  and  some  other  chemical  compounds,  may  be  pro- 
duced of  almost  any  magnitude  that  is  desired." 

QUESTIONS.— How  does  interrupted  crystallization  affect  the  physical  character  of  a 
body  ?  What  curious  tendency  do  crystals  exhibit  in  separating  from  a  solution  t  What 
practical  application  of  this  is  made  in  the  arts  ? 


48  PRINCIPLES     OF     CHEMISTKY. 

guaranty  of  purity,  or  at  least  of  the  absence  of  adultera- 
tion ;  and  hence,  in  medicine,  and  in  the  arts,  many  sub- 
stances are  subjected  to  tedious  and  expensive  processes  for 
no  other  purpose  than  to  cause  them  to  assume  this  form. 

Sea-water,  in  addition  to  salt,  contains  a  variety  of  other  substances,  but 
by  the  process  of  evaporating  the  salt  water  and  crystallizing  the  salt,  most 
of  these  impurities  are  separated.  A  single  crystallization  gives  the  salt  suf- 
ficiently pure  for  commercial  purposes,  but  to  render  it  perfectly  pure,  it  is 
necessary  to  re-dissolve  the  first  crystals  in  pure  water  and  repeat  the  pro- 
cess of  crystallization  several  times. 

This  principle  may  be  demonstrated  by  a  simple  experiment.  If  we  dis- 
solve a  small  quantity  of  common  salt  and  saltpetre  in  warm  water,  and  al- 
low the  solution  to  evaporate  slowly,  the  two  substances,  which  are  intimately 
united  in  the  solution,  will  separate  completely  from  each  other  in  crystal- 
lizing— the  saltpetre  assuming  the  form  of  long  needles  or  prisms,  and  the 
common  salt  the  form  of  cubes.  It  is  in  this  way  that  saltpeter  is  purified 
preparatory  to  being  used  in  the  manufacture  of  gunpowder. 

If  two  bodies,  however,  which  crystallize  in  the  same 
form,  be  mingled  in  solution,  they  can  not  be  separated 
from  each  other  by  crystallization. 

The  difference  in  the  crystallizing  properties  of  silver  and  lead  has  been 
taken  advantage  of  in  a  recent  invention  for  separating  a  small  quantity  of 
silver  which  exists  in  almost  all  the  ores  of  lead.  The  two  metals  are  melted 
and  allowed  to  cool  slowly  ;  the  silver,  forming  into  crystals  more  easily  than 
the  lead,  solidifies  first,  and  the  lead  remaining  is  poured  off. 

62.  Change  in  Bulk, — Many  substances  in  crystallizing, 
or  in  passing  from  a  liquid  to  a  solid  state,  experience  a 
change  in  bulk. 

Water,  at  the  moment  of  congelation,  increases  in  bulk,  and  expands  with 
an  almost  irresistible  force.  As  an  illustration,  the  following  experiment 
may  be  quoted  : — Cast-iron  bomb-shells,  thirteen  inches  in  diameter  and  two 
inches  thick,  were  filled  with  water,  and  their  apertures  or  fuse-holes  firmly 
plugged  with  iron  bolts.  Thus  prepared,  they  were  exposed  to  the  severe 
cold  of  a  Canadian  winter,  at  a  temperature  of  about  19°  below  zero.  At 
the  moment  the  water  froze,  the  iron  plugs  were  violently  thrust  out,  and  the 
ice  protruded,  and  hi  some  instances  the  sheUs  burst  asunder,  thus  demon- 
strating the  enormous  interior  pressure  to  which  they  were  subjected  by 
water  assuming  a  solid  state. 


QUESTIONS. — Can  two  substances  in  solution  be  separated  from  each  other  by  the  act 
of  crystallization  ?  What  are  practical  illustrations  of  this  principle  ?  Under  what  circum- 
stances will  crystallization  fail  to  effect  separation  ?  What  physical  change  frequently 
accompanies  crystallization  ?  Illustrate  this  action  in  the  case  of  water. 


CRYSTALLIZATION.  49 

A  1,000  parts  of  water  at  the  freezing  point  become 
dilated,  by  freezing,  1,063  parts. 

Iron,  in  passing  from  a  melted  to  a  solid  state,  expands  in  the  same  manner 
as  water,  a  fact  which  renders  this  metal  most  suitable  for  castings. 

Other  substances,  however,  present  equally  remarkable  instances  of  con- 
traction in  passing  from  a  liquid  to  a  solid  state,  of  which  gold  and  lead  are 
illustrations ;  hence  it  is  impossible  to  obtain  with  either  of  these  metals  a 
fine  casting  from  a  mould. 

63.  Mother  Liquor, — When  a  substance  separates  itself 
in  part  from  a  liquid  by  crystallization,  the  solution  re- 
maining behind  is  termed  the  Mother  Liquor, 

64.  Water  of  Crystallization, — Some  substances  are  not 
capable  of  assuming  a  crystalline  form  until  they  have 
chemically  combined  with  a  certain  definite  amount  of 
water,  termed  the  WATER  OF   CRYSTALLIZATION.     This 
water  is  not  essential  to  the  chemical  composition  of  the 
substance,  but  merely  to  its  existence  in  the  form  of 
crystals. 

Thus,  a  crystal  of  alum  contains  nearly  one  half  its  weight  of  water  chemi- 
cally combined  with  it.  Without  this  water,  alum  could  not  assume  the  crys- 
talline form,  although  it  would  retain  all  its  chemical  properties  unchanged. 
The  existence  of  the  water  of  crystallization  in  alum  may  be  experimentally 
shown  by  placing  a  small  crystal  of  this  substance  upon  a  hot  surface,  when 
it  will  be  observed  to  foam  and  melt,  and  finally  settle  down  into  a  white 
porous  mass.  The  foaming  is  occasioned  by  the  evaporation  of  the  water  of 
crystallization. 

65.  Ef-flo-res'cencc, — Some  substances  containing  water 
of  crystallization,  part  with  it  on  exposure  to  the  atmos- 
phere, and  crumble  down  to  a  fine  powder.     This  action 
is  termed  Efflorescence. 

If  we  place  half  an  ounce  of  crystalline  Glauber's  salts  in  a  warm  place,  it 
will  soon  lose  its  transparency,  and  finally  crumble  into  a  white  powder, 
weighing  hardly  a  quarter  of  an  ounce.  .  This  loss  of  weight  is  entirely  owing 
to  the  evaporation  of  the  chemically  combined  water  which  imparted  to  the 
salt  its  transparency  and  crystalline  form.  Common  salt,  and  saltpetre,  on 
the  contrary,  if  treated  in  a  similar  way,  undergo  no  change  in  either  appear- 
ance, or  weight,  because  they  contain  no  water  of  crystallization. 

66.  Del-i-ques'cence. — When  a  crystalline   substance, 


QUESTIONS. — To  what  extent  will  water  expand  in  freezing  ?  Why  is  iron  eminently 
suitable  for  fine  castings,  and  gold  and  lead  unsuitable?  What  is  a  mother  liquor? 
What  is  water  of  crystallization  ?  What  is  efflorescence?  What  is  deliquescence  ? 

3 


50  P'RINCIPLES   OF   CHEMISTRY. 

on  exposure  to  air,  absorbs  water,  and  becomes  converted 
thereby  into  a  liquid,  or  seini-liquid  mass,  it  is  said  to 
deliquesce,  and  the  phenomenon  is  termed  Deliquescence. 

67.  De-crep-i-la'tioiL — Some  substances,  when  crystal- 
lized rapidly  from  a  solution,  frequently  inclose  mechan- 
ically within  their  texture  small  quantities  of  the  mother 
liquor,  the  expansion  of  which,  when  heated,  bursts  the 
crystals  with  a  sort  of  crackling  explosion.     This  pheno- 
menon is  known  by  the  name  of  Decrepitation. 

This  result  may  be  exhibited  by  throwing  a  small  quantity. of  common 
salt,  which  has  been  crystallized  rapidly,  upon  a  heated  surface.  If  the  salt, 
however,  has  been  crystallized  by  slow  evaporation,  it  will  not  decrepitate. 

68.  Native   Crystals. — The  mineral  kingdom  presents  us  with  the 
most  splendid  examples  of  crystallized  bodies,  many  of  which  the  chemist  is 
able  to  artificially  reproduce  in  his  laboratory.     Within  the  last  few  years, 
M.  Ebelman,  an  eminent  French  chemist,  has  succeeded  in  producing  some 
of  the  most  valuable  gems — as,  for  example,  the  emerald  and  the  ruby — by 
mixing  together  in  proper  proportions  the  elementary  substances  which  enter 
into  their  composition,  and  then  exposing  the  compound  to  the  long-continued 
and  intense  heat  of  a  furnace  used  for  baking  porcelain. 

Some  native  crystals,  however,  seem  to  be  beyond  the  power  of  art  to 
imitate.  Of  these,  the  diamond  is  perhaps  the  most  remarkable.  This  body 
consists  of  pure  carbon  (the  same  substance  with  which  we  are  familiar  as 
charcoal  and  as  black-lead),  but  which  can  not  be  either  fused  or  dissolved, 
and  consequently  can  not  be  crystallized  by  any  means  at  present  known. 
Such  means  have  been  eagerly  sought  for,  however,  since  the  discovery  of 
the  composition  of  the  diamond,  and  there  seems  no  reason  why  they  should 
not  at  some  period  be  discovered. 

The  most  perfect  crystals  of  gems  are  met  with  in  nature  of  only  a  moder- 
ate size.  The  larger  ones  are  less  clear,  and  wanting  in  transparency  and 
luster.  The  emerald,  sufficiently  pure  for  jewelry,  does  not  often  exceed  an 
inch  in  length,  and  seldom  so  much  as  this.  Transparent  sapphires  above  an 
inch  in  length  are  very  rare.  Crystals  of  quartz  are  sometimes  found  of  very 
large  size.  One  at  Milan  measures  3J  feet  in  length,  5|  in  circumference, 
and  weighs  870  pounds. 

69.  Formation  of  Crystals  in  Solid  Bodies,— A  very  re- 
markable change,  a  variety  of  crystallization,  sometimes 
takes  place  in  the  form  and  arrangement  of  the  particles 
of  solid  bodies,  without  their  undergoing  any  alteration 

QUESTIONS. — What  is  decrepitation  ?  Where  are  the  most  splendid  examples  of  crystal- 
lized bodies  to  be  met  with  ?  Are  any  native  crystals  capable  of  being  reproduced  by 
art  ?  What  crystallized  body  can  not  be  imitated  ?  What  remarkable  change  sometimes 
takes  place  in  the  particles  of  solid  bodies  ? 


CRYSTALLIZATION.  51 

from  the  solid  to  the  liquid  state.  This  subject  is  one  of 
great  importance,  and  its  investigation  has  furnished  a 
partial  solution  of  some  phenomena  that  were  once  re- 
garded as  inexplicable. 

The  simplest  illustration  of  this  action  is  to  be  found  in  the  case  of  sugar. 
"When  this  substance  is  melted  and  allowed  to  cool,  it  forms  a  perfectly  trans- 
parent, hard  mass,  without  the  slightest  trace  of  crystalline  arrangement ;  but 
after  some  months  it  loses  its  transparency,  becomes  white,  crystalline,  and 
brittle.  Similar  changes  take  place  also  in  many  other  bodies,  but  in  cases 
of  this  character  the  cause  which  produced  the  result  described  Is  not  cer- 
tainly known,  and  has  been  ascribed  to  the  action  of  several  forces. 

The  following  illustrations  are  of  a  somewhat  different  character.  If  we 
submit  a  piece  of  metal,  even  the  toughest,  to  long-continued  hammering,  or 
jarring,  the  atoms,  or  particles  of  which  it  is  composed,  seem  to  take  on  a 
new  arrangement,  and  the  metal  gradually  loses  all  its  tenacity,  flexibility, 
malleability,  and  ductility,  and  becomes  brittle. 

The  surface  of  a  fresh  fracture,  under  such  circumstances,  exhibits  a  dis- 
tinctly crystalline  structure.  The  tenacity  of  a  metal  thus  rendered  brittle 
may  be  restored  again  in  great  measure  by  heating  and  slowly  cooling — a 
process  known  in  the  arts  as  ;<  annealing." 

A  great  number  of  other  instances  illustrative  of  the  effect  of  jarring  and 
concussion  on  the  structure  of  metals,  might  also  bo  adduced.  Coppersmiths, 
who  form  vessels  of  brass  and  copper  by  the  hammer  alone,  can  work  on  them 
only  for  a  short  time  before  they  require  annealing ;  otherwise  they  would 
crack  and  fly  into  pieces. 

For  similar  reasons,  a  cannon  can  only  be  fired  a  certain  number  of  times 
before  it  will  burst,  and  a  cannon  which  has  been  long  in  use,  although  ap- 
parently sound,  is  always  condemned  and  broken  up.  The  tone  of  a  bell, 
during  the  two  or  three  first  years  of  use,  uniformly  increases  in  strength, 
owing  probably  to  a  change  in  the  arrangement  of  the  particles  under  the 
hammering  action  in  ringing. 

A  more  important  illustration,  and  one  that  more  closely  affects  our  inter- 
ests, is  the  liability  of  railroad  car-axles  and  wheels  to  break  from  the  same 
cause.  A  car-axle,  after  a  long  lapse  of  time  and  use,  is  almost  certain  to 
break. 

The  explanation  of  these  changes,  especially  in  the  case  of  iron,  is  as  fol- 
lows : — The  particles  of  cast-iron,  as  may  be  seen  by  the  naked  eye,  are  crystals, 
more  or  less  perfect  in  form,  and  aggregated  together  by  the  force  of  cohesion. 
In  the  conversion  of  cast-iron  into  wrought-iron,  each  crystal  by  heating,  ham- 
mering, and  rolling,  is  gradually  elongated  into  a  thread,  so  that  wrought-iron 
is  an  aggregation  of  fibers  (fibrous  iron,  as  it  is  sometimes  called),  or  a  series 
of  threads  kept  together  by  the  force  of  cohesion.  When  now  a  bar  of  cold, 

QUESTIONS Give  an  illustration.     How  is  the  strength  of  iron  and  other  metals  affected 

by  hammering,  jarring,  etc.  ?  Under  what  circumstances  will  cannon  burst,  and  railway 
axles  break  ?  What  explanation  has  been  given  of  these  phenomena '? 


52  PRINCIPLES    OF    CHEMISTRY. 

wrought,  or  fibrous  iron  is  made  to  vibrate  by  shocks  communicated  either 
by  blows  of  a  hammer,  or  by  the  rapping  of  any  part  of  a  machine,  or  by  the 
continued  rolling  and  jarring  of  a  railway  car  upon  the  rails,  the  little  fine 
threads,  or  fibers  snap  one  by  one,  and  the  particles  return  to  their  original 
crystalline,  or  granular  state,  and  by  this  change  the  entire  mass  is  rendered 
brittle. 

70.  Primary  Forms  of  Crystals.— The  apparently  innu- 
merable variety  of  figures  which  various  substances  as- 
sume in  crystallizing,  may  all  be  referred  to  a  few  regular 
and  fundamental  forms. 

Each  substance  has  a  characteristic  form  of  crystal, 
which  is  termed  its  Primary  Form. 

Variations  of  this  original  form,  which  may  take  place 
to  any  extent  so  long  as  a  correspondence  of  angles  is 
preserved,  are  termed  Secondary  Forms. 

The  number  of  primary  or  fundamental  forms  to  which 
all  other  crystalline  solids  may  be  referred  is  six — the 
cube,  the  square  prism,  the  right  rectangular  prism,  the 
oblique  rhombic  prism,  the  oblique  rhomboidal  prism,  and 
the  hexagonal  prism,  or  rhombohedron. 

The  number  of  secondary  forms  is  almost  innumerable, 
all  of  which  are  modifications  of  the  six  primary  forms. 

Thus,  carbonate  of  li me  has  been  found  crystallized  in  more  than  six  hun- 
dred different  secondary  forms,  but  all  of  them  are  related  to  each  other,  and 
are  derivable  from  one  original  primary  figure,  the  rhombohedron. 

The  study  of  the  geometrical  relations  of  the  different  crystalline  forms  to 
each  other,  belongs  to  the  science  of  crystallography.  The  investigations  of 
chemistry,  however,  have  contributed  much  to  our  knowledge  of  the  laws 
and  forces  which  govern  the  production  of  crystals,  and  have  furnished  some 
explanation  of  the  reason  why  the  several  atoms,  each  invisible  on  account 
of  its  minuteness,  should  arrange  themselves  in  the  same  manner,  and  in 
the  fitting  place,  so  as  to  build  up  a  cubical  or  prismatic  crystal,  rather  than 
an  incoherent  mass,  shapeless  and  devoid  of  regularity. 

71.  Theory  of  Crystallization.— It  is  supposed  that  the 
atoms,  or  molecules  which  make  up  the  body  of  a  crystal, 
are  possessed  of  polarity  ;  or,  in  other  words,  that  the  two 
opposite  sides  of  the  atoms  are  like  the  two  opposite  poles 

QUKSTIONS. — What  is  understood  by  primary  and  secondary  forms  of  crystals?  Ilovf 
many  primary>  or  fundamental  forms  of  crystals  are  recognized  ?  How  many  secondary 
forms  exist  ?  Give  an  illustration  of  the  primary  and  secondary  forms  of  carbonate  of 
lime.  Explain  the  general  theory  of  crystallization. 


CRYSTALLIZATION. 


53 


of  a  magnet,  endowed  with  opposite  forces.  FIG.  17. 
The  action  of  these  forces  compels  the  atom, 
in  assuming  its  place  in  a  crystal,  to  maintain 
a  certain  direction  as  respects  the  contiguous 
particles  (see  Fig.  17),  in  the  same  way  that 
the  action  of  the  magnetic  forces  on  a  bar  of 
steel  compels  it  to  maintain  a  constant  direc- 
tion as  regards  the  poles  of  the  earth. 

That  the  strength  of  the  directive  force  which  influences 
the  atoms  of  matter  to  assume  a  symmetrical  arrangement 
is  not  feeble  or  insignificant,  is  clearly  shown  by  the  enor- 
mous power  which  crystallizing  action  exerts.  Thus,  the  expansive  force 
of  water  in  freezing,  illustrations  of  which  are  most  familiar,  is  due  entirely  to 
a  re-arrangement  of  the  particles  in  crystallizing,  and  a  consequent  occupa- 
tion of  more  space. 

The  direction  in  which  the  supposed  polar  forces  act,  or 
the  lines  in  which  the  particles  arrange  themselves  in  or- 
der to  build  up  symmetrical  solids,  are  termed  the  axes 
of  the  crystal. 

Variations  in  the  number  or  arrangement  of  these  lines  or  axes,  necessarily 
modify  the  geometrical  form  of  the  crystal,  and  a  consideration  of  the  relation 
•which  the  multitude  of  crystalline  forms  sustain  to  each  other 
through  their  axes,  or  symmetrical  lines  of  formation,  has  en- 
abled us  to  select  six  primary  forms  from  which  all  the  others 
may  be  derived. 

Thus,  in  the  first  primary  form,  Fig.  18,  which  is  the  cubical, 
or  regular  form,  there  are  three  axes,  a  a  a,  all  equal  and  cross- 
ing each  other  at  the  center  of  the  crystal  at  right  angles.  The  same  arrange- 
ment of  axes  holds  good  in  all  the  secondary  forms  which  are  derived  from  this 
primary  form ;  and  in  consequence  of  this  are  all  regular.  In  the  second 
primary  form,  the  square  prism,  Fig.  19,  there  are  three  axes,  all  of  them  at 
right  angles  to  each  other,  but  only  two,  a  a,  a  a,  are  of  equal  length ;  the 
third,  c  c,  being  either  longer  or  shorter  than  the  others.  pIG  ^9 

Similar  variations  exist,  also,  in  the  number  or  inclination  of 
the  axes  of  the  other  primary  forms. 

Many  facts  in  science  seem  to  prove  that  the  existence  of  axes 
in  crystals  is  not  imaginary,  but  real.  Thus,  when  the  arrange- 
ment of  a  crystalline  body  is  perfectly  symmetrical,  as  it  is  in  all 
crystals  belonging  to  the  cubical  system,  the  transmission  of  light, 
the  expansion  of  heat,  the  conducting  power  of  heat,  and  probably 


FIG.  18. 


QUESTIONS. — What  are  the  axes  of  a  crystal  ?  On  what  ground  do  we  recognize  six 
primary  forms  of  crystalline  solids  ?  What  facts  in  science  seem  to  prove  that  the  axes 
of  crystals  have  a  real  existence  ? 


54  PRINCIPLES    OF     CHEMISTRY. 

the  power  of  transmitting  sound,  electricity,  and  magnetism,  is  uniform  in 
every  direction ;  but  when  the  axes  of  a  crystal  are  unequal ;  or,  in  other 
words,  when  the  action  of  the  molecular  force  which  has  given  direction  to 
the  atoms  and  shaped  the  crystal,  is  more  powerful  in  one  direction  than  in 
another,  an  irregularity  in  the  action  of  the  body  on  light,  and  in  its  expan- 
sive and  conductive  powers  for  heat,  may  be  immediately  traced. 

I-so-morph'ism, — The  term  Isomorphism  (equal  forms) 
is  applied  to  those  bodies  which  can  be  substituted  for  one 
another  in  a  chemical  compound,  without  producing  any 
change  in  the  crystalline  form  of  that  compound.  This 
property,  is  restricted  to  a  comparatively  few  substances. 

Thus,  an  oxyd  of  zinc  may  replace  or  be  substituted  for  oxyd  of  magnesia, 
and  an  oxyd  of  iron  for  an  oxyd  of  copper,  in  a  chemical  compound,  without 
causing  any  alteration  of  crystalline  form.  As  a  general  rule,  however,  the 
change,  or  substitution  of  one  element  of  a  chemical  compound  for  another' 
of  different  character,  occasions  a  change  in  the  crystalline  form  of  the  com- 
pound. 

The  consideration  of  isomorphism  is  of  great  importance  in  chemistry,  and 
has  added  much  to  our  knowledge  respecting  the  nature  of  the  elementary 
atoms  of  matter.  A  study  of  its  principles,  among  other  results,  has  estab- 
lished the  existence  of  such  curious  relations  between  certain  of  the  so-called 
elementary  substances,  as  to  suggest  their  derivation  from  some  common  and 
unknown  form  of  matter.  This  subject,  under  another  department,  will, be 
again  referred  to. 

72.  Di-morph'ism, — The  rule  that  all  the  crystalline  fig- 
ures of  any  particular  substance  may  be  derived  from  the 
same  ultimate  form,  is  subject  to  several  exceptions.  Some 
substances  are  capable  of  assuming  two  forms  of  crystals, 
according  to  the  temperature  at  which  they  are  produced, 
which  are  geometrically  incompatible  with  each  other ; 
and  this  difference  of  crystalline  form  is  associated  with 
difference  of  specific  gravity,  hardness,  color,  and  other 
properties.  Such  bodies  are  termed  Dimorphous  (two- 
formed). 

The  crystals  of  sulphur  found  in  nature,  and  the  crystals  obtained  by  the 
slow  cooling  of  a  melted  mass  of  sulphur,  are  entirely  different.  A  beautiful 
instance  of  this  kind  is  afforded  by  a  compound  of  iodine  and  mercury,  known 
as  the  iodide  of  mercury.  The  minute  particles  of  this  substance  are  of  a 
brilliant  scarlet  color,  but  by  the  application  of  heat  their  crystalline  arrange- 
ment is  changed,  and  the  change  is  rendered  visible  to  the  eye  by  the  sub- 

QTTESTTONS.— What  is  isomorphism?  Give  an  illustration.  What  is  dimorphism? 
What  are  examples  ? 


CRYSTALLIZATION.  55 

stitution  of  a  bright  yellow  color  in  place  of  the  scarlet  When  the  substance 
has  become  cool,  the  application  of  a  slight  mechanical  force,  such  as  a  mere 
scratch  upon  a  single  point,  will  change  the  crystalline  arrangement  back  to 
its  original  condition,  and  instantly  restore  the  original  color. 

Some  few  substances  are  even  trimorphous ;  that  is,  they  crystallize  in 
three  different  forms, 

73.  C lea v' age, — Crystals  can  not  be  broken  with,  equal 
readiness  in  all  directions,  but  they  have  a  tendency  to 
split  or  divide  according  to  certain  determinate  lines. 
This  property  is  termed  the  Cleavage  of  the  crystal. 

Cleavage  will  often  enable  us  to  detect  crystalline  structure  in  a  body  which 
at  first  appears  as  a  shapeless  mass.  Thus,  in  the  case  of  the  very  common 
mineral  known  as  "  Iceland  spar,"  which  is  a  variety  of  carbonate  of  lime,  if 
we  strike  gently  upon  an  irregular  fragment  with  a  hammer,  we  shall  find 
that  the  lines  in  which  fracture  occurs  are  all  inclined  to  each  other  at  angles 
of  105  degrees,  and  in  consequence  of  this,  the  detached  particles  have  all 
the  form  of  rhombohedrons.  In  like  manner,  mica  splits  only  in  leaves,  and 
galena,  the  name  applied  to  the  common  ore  of  lead,  only  in  cubes. 

This  property  of  crystals  has  long  been  known  to  jew- 
elers, who  have  profited  by  it  to  alter  the  form  of  precious 
stones,  in  place  of  resorting  to  the  expensive  process  of 
cutting.  Thus,  the  diamond  will  split  with  a  smooth  sur- 
face in  four  directions,  and  by  taking  advantage  of  this, 
a  thin  layer  on  a  defective  side  may  be  smoothly  removed 
at  a  single  operation. 

A  property  analogous  to  the  cleavage  of  crystals  may 
be  observed  in  bodies  of  a  different  character.  Thus,  wood 
splits  with  greater  facility  in  a  direction  parallel  to  its 
fibers  than  at  right  angles  to  them,  or,  as  it  is  termed, 
"  across  the  grain/' 


QUESTIONS — What  is  cleavage  ?  How  will  cleavage  often  enable  us  to  detect  crystal- 
line structure  in  an  irregular  body  ?  What  practical  application  has  been  made  of  the 
cleavage  of  crystals  ? 


56  PRINCIPLES     OF     CHEMISTRY. 

CHAPTER   II, 

HEAT. 

74.  Heat  and  Chemical  Action, — Almost  every  form  of 
chemical  action  is  influenced  to  a  greater  or  less  extent  by 
the  agency  of  heat.     A  general  knowledge,  therefore,  of 
the  principles  and  applications  of  heat  is  essential  to  a 
correct  understanding  of  the  science  of  chemistry. 

Heat  and  Caloric, — Heat  is  a  physical  agent,  known  only 
"by  its  effects  upon  matter.  In  ordinary  language  we  use 
the  term  heat  to  express  the  sensation  of  warmth.  Ca- 
loric is  the  general  name  given  to  the  physical  agent  which 
produces  the  sensation  of  warmth,  and  the  various  effects 
of  heat  observed  in  matter. 

75.  Two  Conditions  of  Heat, — Heat  exists  in  two  very 
different  conditions,  as  FREE,  or  SENSIBLE  HEAT,,  and  as 
LATENT  HEAT/5 

When  the  heat  retained  or  lost  by  a  body  is  attended 
with  a  sense  of  increased  or  diminished  warmth,  it  is  called 
sensible  heat. 

When  the  heat  retained  or  lost  by  a  body  is  not  per- 
ceptible to  our  sense,  it  is  called  latent  heat.f 

76.  Measurement  of  Heat. — The  quantity  of  heat  ob- 
served in  different  substances  is  measured,  and  its  effects 
on  matter  estimated,  only  by  the  change  in  bulk,  or  ap- 
pearance, which  different  bodies  assume,  according  as  heat 
is  added  or  subtracted. 

77.  Distinguishing  Characteristic  of  Heat,— Heat  pos- 
sesses a  distinguishing  characteristic  of  passing  through 
and  existing  in  all  kinds  of  matter  at  all  times.     So  far  as 

*  Latent,  from  the  Latin  word  lateo,  to  be  hid, 

t  The  phenomena  of  latent  heat  are  further  considered  under  the  head  of  Liquefaction 
and  Vaporisation. 

QUESTIONS.— What  relation  exists  between  heat  and  chemistry?  What  is  heat?  De- 
fine the  meaning  of  the  term  caloric.  In  what  two  conditions  does  heat  exist  ?  What  is 
free,  or  sensible  heat  ?  What  is  latent  heat  2  How  is  heat  measured  ?  What  is  the  dis- 
tinguishing characteristic  of  heat? 


HEAT.  67 

we  know,  heat  is  everywhere  present,  and  every  body  that 
exists  contains  it  without  known  limits. 

Ice  contains  heat  in  large  quantities.  Sir  Humphrey  Davy,  by  friction,  ex- 
tracted heat  from  two  pieces  of  ice,  and  quickly  melted  them,  in  a  room  cooled 
below  the  freezing-point,  by  rubbing  them  against  each  other, 

78.  Temperature,— The  amount  of  sensible  heat  a  body 
contains  is  called  its  temperature, 

The  temperature  of  a  body  affords  no  indication  of  the  real  quantity  of  heat 
which  it  contains.  A  pint  of  boiling  water  will  raise  a  thermometer  to  the 
same  degree  as  a  gallon  of  the  game  water ;  yet  it  is  obvious  that  the  larger 
quantity  of  liquid  contains  the  greater  amount  of  heat 

Cold  is  a  relative  term  expressing  only  the  absence  of 
heat  in  a  degree  ;  not  its  total  absence,  for  heat  exists 
always  in  all  bodies. 

A  body  may  feel  hot  and  cold  to  the  same  person  at  the  same  time,  since 
the  sensation  of  heat  is  produced  by  a  body  colder  than  the  hand,  provided 
it  be  less  cold  than  the  body  touched  immediately  before ;  and  the  sensation 
of  cold  is  produced  under  the  opposite  circumstances,  of  touching  a  compara- 
tively warm  body,  but  which  is  less  warm  than  some  other  body  touched  pre- 
viously. Thus,  if  a  person  transfer  one  hand  to  common  spring  water  imme- 
diately after  touching  ice,  to  that  hand  the  water  would  feel  very  warm  ;  while 
the  other  hand,  transferred  from  warm  water  to  the  spring  water,  would  feel  a 
sensation  of  cold. 

It  is  a  very  curious  fact,  that  intense  cold  produces  the  same  sensation  as 
intense  heat.  Frozen  mercury  will  blister  the  part  to  which  it  is  applied  in 
the  same  manner  as  red  hot  iron ;  and  the  physiological  action  of  a  freezing 
mixture  resembles  that  of  boiling  water.  Sensations  of  heat  and  cold  are, 
therefore,  merely  degrees  of  temperature,  contrasted  by  name  in  reference  to 
the  peculiar  temperature  of  the  individual  speaking  of  them. 

79.  Diffusion  of  Heat,— The  tendency  of  heat  is  to  dif- 
fuse, or  spread  itself  among  all  neighboring  substances, 
until  all  have  acquired  the  same,  or  a  uniform  temperature. 

A  piece  of  iron  thrust  into  burning  coals  becomes  hot  among  them,  because 
the  heat  passes  from  the  coals  into  the  iron,  until  the  metal  has  acquired  an 
equal  temperature. 

80.  Heat  Imponderable, — Heat  is  imponderable,  or  does 
not  possess  any  perceptible  weight. 

If  we  balance  a  quantity  of  ice  in  a  delicate  scale,  and  then  leave  it  to 


. — What  is  temperature  ?  Does  the  temperature  of  a  body  indicate  the  actual 
quantity  of  heat  it  contains  ?  What  is  cold  ?  May  a  body  feel  hot  and  cold  at  the  same 
time  ?  What  are  sensations  of  heat  and  cold  ?  In  what  manner  does  heat  diffuse  itself  ? 
Does  heat  possess  weight  ? 

o* 


58  PRINCIPLES    OF    CHEMISTRY. 

melt,  the  equilibrium  will  not  be  in  the  slightest  degree  disturbed.  If  we 
substitute  for  the  ice  boiling  water,  or  red  hot  iron,  and  leave  this  to  cool, 
there  will  be  no  difference  in  the  result.  Count  Rumford,  having  suspended 
a  bottle  containing  water,  and  another  containing  alcohol,  to  the  arms  of  a 
balance,  and  adjusted  them  so  as  to  be  exactly  in  equilibrium,  found  that  the 
balance  remained  undisturbed  when  the  water  was  completely  frozen,  though 
the  heat  the  water  had  lost  must  have  been  more  than  sufficient  to  have  made 
an  equal  weight  of  gold  red  hot. 

81.  Theory  of  Heat, — The  nature,  or  cause  of  heat  is  not 
clearly  understood.  Two  explanations,  or  theories,  have 
been  proposed  to  account  for  the  various  phenomena  of 
heat,  which  are  known  as  the  mechanical  and  vibratory 
theories. 

Mechanical  Theory, — The  mechanical  theory  supposes 
heat  to  he  an  extremely  subtile  fluid,  or  ethereal  kind  of 
matter  pervading  all  space,  and  entering  into  combination 
in  various  proportions  and  quantities,  with  all  bodies,  and 
producing  by  this  combination  all  the  various  effects  no- 
ticed. 

Vibratory  Theory,— The  vibratory  theory,  on  the  con- 
trary, supposes  heat  to  be  merely  the  effect  of  a  species 
of  motion,  like  a  vibration  or  undulation,  produced  either 
in  the  constituent  particles  of  bodies,  or  in  a  subtile,  im- 
ponderable fluid  which  pervades  them. 

"When  one  end  of  a  bar  of  iron  is  thrust  into  the  fire  and  heated,  the  other 
end  soon  becomes  hot  also.  According  to  the  mechanical  theory,  a  subtile 
fluid  coming  out  of  the  fire  enters  into  the  iron,  and  passes  from  particle  to 
particle  until  it  has  spread  through  the  whole.  When  the  hand  is  applied  to 
the  bar  it  passes  into  it  also,  and  occasions  the  sensation  of  warmth.  Ac- 
cording to  the  vibratory  theory,  the  heat  of  the  fire  communicates  to  the  par- 
ticles of  the  iron  themselves,  or  to  a  subtile  fluid  pervading  them,  certain  vi- 
bratory motions,  which  motions  are  gradually  transmitted  in  every  direction, 
and  produce  the  sensation  of  heat,  in  the  same  way  that  the  undulations  or 
vibrations  of  air,  produce  the  sensation  of  sound. 

The  fact  that  vibrations  do  occur  in  masses  of  metal  and  other  substances 
during  the  passage  of  heat  through  them,  can  be  demonstrated  by  experi- 
ment. Thus,  if  an  irregularly  curved  bar  of  hot  brass  be  laid  upon  a  sup- 
port of  cold  lead,  the  bar  will  be  thrown  into  a  vibratory  state,  accompanied 


QUESTIONS.— What  two  theories  have  been  proposed  to  account  for  the  origin  of  heat  ? 
What  is  the  mechanical  theory?  What  is  the  vibratory  theory?  Illustrate  the  sup- 
posed production  of  heat  in  accordance  with  the  two  theories. 


HEAT,  59 

by  a  somewhat  musical  sound  and  a  rocking  motion;  and  this  action  con- 
tinues so  long  as  an  inequality  of  temperature  exists  between  the  two  metals. 

There  seems  to  be  but  little  doubt  at  the  present  time  among  scientific  men, 
that  the  theory  which  ascribes  the  phenomena  of  heat  to  a  series  of  vibra- 
tions, or  undulations,  either  in  matter,  or  a  fluid  pervading  it,  is  substantially 
correct.  At  the  same  time  it  is  not  wholly  satisfactory,  and  neither  theory 
will  perfectly  explain  all  the  facts  in  relation  to  heat  with  which  we  are  ac- 
quainted. For  the  purpose  of  describing  and  explaining  the  phenomena  and 
effects  of  heat,  it  is  convenient,  in  many  cases,  to  retain  the  idea  that  heat  is 
a  substance. 

The  fact  that  nature  nowhere  presents  us,  neither  has  art  ever  succeeded 
in  showing  us,  heat  alone  in  a  separate  state,  is  a  strong  ground  for  believing 
that  heat  has  no  separate  material  existence.  Heat,  moreover,  can  be  pro- 
duced without  limit  by  friction,  and  intense  heat  is  also  produced  by  the  ex- 
plosion of  gunpowder.  On  the  contrary,  as  arguments  in  favor  of  the  mate- 
rial existence  of  heat,  we  have  the  fact,  that  heat  becomes  instantly  sensible 
on  the  condensation  of  any  material  mass,  as  if  it  were  squeezed  out  of  it :  as 
when,  on  reducing  the  bulk  of  a  piece  of  iron  by  hammering,  we  render  it 
red  hot  (the  greatest  amount  of  heat  being  emitted  with  the  blows  that  most 
change  its  bulk). 

It  is  also  very  remarkable,  that  iron  once  heated  in  this  way  can  not  again  be 
made  red  hot  by  hammering  until  it  has  again  been  heated  in  a  fire.  Finally, 
the  laws  of  the  spreading  of  heat  do  not  resemble  those  of  the  spreading  of 
sound,  or  of  any  other  motion  known  to  us. 

82.  Relations  of  Light  and  Heat, — The  relation  between  heat 
and  light  is  a  very  intimate  one.  Heat  exists  without  light,  but  all  the  ordi- 
nary sources  of  light  are  also  sources  of  heat ;  and  by  whatever  artificial  means 
natural  light  is  condensed,  so  as  to  increase  its  splendor,  the  heat  which  it 
produces  is  also,  at  the  same  time,  rendered  more  intense. 

Incandescence, — When  a  body,  naturally  incapable  of 
emitting  light,  is  heated  to  a  sufficient  extent  to  become 
luminous,  it  is  said  to  be  incandescent,  or  ignited. 

Flame, — Flame  is  a  luminous  vapor  issuing  from  a  burn- 
ing body.  Fire  is  the  appearance  of  heat  and  light  in 
conjunction,  produced  by  the  combustion  of  inflammable 
substances. 

The  ancient  philosophers  used  the  term  fire  as  a  characteristic  of  the  nature 
of  heat,  and  regarded  it  as  one  of  the  four  elements  of  nature  ;  air,  earth,  and 
water  being  the  other  three. 


QUESTIONS.— Which  theory  is  generally  received  ?    What  relations  exist  between  light 
and  heat?    Define  incandescence.     What  is  flame?    What  is  fire? 


60  PRINCIPLES     OF     CHE  MIST  BY. 

SECTION    I. 

SOURCES    OF    HEAT. 

83.  Sources  of  Heat,—  The  principal  sources  of  heat  of 
which  practical  advantage  may  be  taken,  are  the  sun,  me- 
chanical action,  chemical  action,  and  electricity. 

84.  The  Sun  a  Source  of  Heat,—  The  greatest  natural 
source  of  heat  is  the  sun,  as  it  is  also  the  greatest  natural 
source  of  light. 

Although  the  quantity  of  heat  sent  forth  from  the  sun  is  Immense,  its 
rays,  falling  naturally,    are  never  hot  enough,  even  in  the  torrid  zoner  to 
FiG.  20.  kindle  combustible  substances.    By  means,  however, 

of  a  burning-glass,  the  heat  of  the  suurs  rays  can  be 
concentrated,  or  bent  toward  one  point,  called  a  focus, 
in  sufficient  quantity  to  set  fire  to  substances  submitted 
to  their  action. 

Fig.  20  represents  the  manner  in  which  a  burning- 
glass  concentrates  or  bends  down  the  rays  of  heat 
until  they  meet  in  a  focus* 

The  greatest  natural  temperature  ever  authentically  re- 
corded was  at  Bagdad,  in  1819,  when  the  thermometer 
(Fahrenheit's)  rose  to  120°  in  the  shade.  On  the  west 
coast  of  Africa  the  thermometer  has  been  observed  as 
high  as  108°  F.  in  the  shade.  Burckhardt  in  Egypt,  and 
Humboldt  in  South  America,  observed  it  at  117°  F.  in 
the  shade. 

About  70°  below  the  zero  of  Fahrenheit's  thermometer 
is  the  lowest  atmospheric  temperature  ever  experienced 
"by  the  Arctic  navigators. 

The  greatest  artificial  cold  ever  measured  was  220°  F. 
below  zero. 

This  temperature  was  obtained  some  years  siuee  by  M.  Natterer,  a  German 
chemist.  Professor  Faraday  has  also  produced  a  cold  of  166°  F.  below 
zero.  Neither  of  these  experimenters  succeeded  in  freezing  pure  alcohol  or 
ether. 

The  estimated  temperature  of  the  space  above  the  earth's  atmosphere  has 
been  estimated  at  58°  below  zeror  Fahrenheit's  thermometer, 


.  —  What  are  the  principal  sources  of  heat?  What  is  the  greatest  source  of 
heat  ?  What  is  the  greatest  natural  temperature  ever  observed  ?  What  is  the  lowest 
natural  temperature  observed?  What  is  the  greatest  artificial  cold  ever  measured? 


SOURCES     OF    HEAT.  61 

85.  Mechanical  Action,  considered  as  a  source  of  heat, 
includes  friction  and  compression,  or  percussion. 

Friction,— The  supply  of  heat  which  can  be  derived 
from  friction  is  apparently  unlimited. 

Savage  nations  kindle  a  fire  by  the  friction  of  two  pieces  of  dry  wood ; 
the  axles  of  wheels  revolving  rapidly  frequently  become  ignited ;  and  in  the 
boring  and  turning  of  metal  the  chisels  often  become  intensely  hot.  In  all 
these  cases  the  friction  of  the  surfaces  of  wood  or  of  metal  in  contact  dis- 
turbs the  latent  heat  of  these  substances,  and  renders  it  sensible. 

The  following  interesting  experiment  was  made  by  Count  Rumford,  to  il- 
lustrate the  effect  of  friction  in  producing  heat : — A  borer  was  made  to  re- 
volve in  a  cylinder  of  brass,  partially  bored,  thirty-two  times  in  a  minute. 
The  cylinder  was  inclosed  in  a  box  containing  18  pounds  of  water,  the  tem- 
perature of  which  was  at  first  60°,  but  rose  in  an  hour  to  107°;  and  in 
two  hours  and  a  half  the  water  boiled.  The  heat  thus  obtained  was  calcu- 
lated to  be  somewhat  greater  than  that  given  out  during  the  same  period  by 
the  burning  of  nine  wax  candles,  each  f  ths  of  an  inch  in  diameter. 

Recent  experiments  made  by  Mr.  Joule  of  England,  appear  to  show  that 
the  actual  quantity  of  heat  developed  by  friction  is  dependent  simply  upon 
the  amount  of  force  expended,  without  regard  to  the  nature  of  the  substances 
rubbed  together.  Ho  found,  as  the  result  of  a  great  number  of  experiments, 
that  when  water  was  agitated  by  means  of  a  horizontal  brass  wheel,  which 
was  made  to  revolve,  as  the  wheels  of  a  clock  are,  by  the  descent  of  a  weight, 
that  the  temperature  of  the  water  was  increased  by  friction  against  the 
metal ;  and  that  in  this  way,  one  pound  of  water  could  be  raised  in  tempera- 
ture one  degree  by  an  expenditure  of  an  amount  of  force  sufficient  to  raise 
772  pounds  weight  to  the  height  *of  one  foot.  When  cast-iron  was  rubbed 
against  iron,  the  force  required  to  produce  heat  by  friction  sufficient  to  ele- 
vate the  temperature  of  a  pound  of  water  one  degree,  was  found  to  be  equiva- 
lent to  775  pounds,  and  when  iron  was  rubbed  against  mercury,  to  774  pounds, 

It  thus  appears  from  these  experiments,  that  force  expended  in  producing 
friction  is  converted  into  heat,  and  that  when  a  pound  of  water  is  elevated  in 
temperature  one  degree,  some  force  equivalent  to  the  raising  of  a  weight  of 
about  772  pounds  to  the  height  of  one  foot  is  always  exerted.* 


*  This  discovery,  that  heat  and  mechanical  power  are  mutually  convertible,  and  that 
the  relation  between  them  is  definite,  722  foot-pounds  of  motive  power  being  equivalent  to 
a  unit  of  heat — that  is,  to  the  amount  of  heat  requisite  to  raise  a  pound  of  -water  through 
one  degree  of  Fahrenheit— is  one  of  the  most  interesting  of  modern  science,  and  has  led 
to  many  important  deductions.  Thus,  force  is  expended  by  friction  in  the  ebb  and  flow 
of  every  tide,  and  must,  therefore,  reappear  as  heat.  According  to  the  computations  of 
Bessel,  the  astronomer,  25,000  miles  of  water  flow  in  every  six  hours  from  one  quarter  of 

QUESTIONS.— What  does  mechanical  action,  considered  as  a  source  of  heat,  include? 
What  is  said  of  the  development  of  heat  by  friction  ?  What  experiments  were  made  by 
Count  Rumford  ?  What  has  recently  been  determined  respecting  the  production  of  heat 
by  friction  I 


62  PRINCIPLES     OF     CHEMISTRY. 

Compression. — The  reduction  of  matter  into  a  smaller 
compass  by  an  external  or  mechanical  force,  is  generally 
attended  with  an  evolution  of  heat.  To  such  an  act  of 
compression  we  apply  the  term  condensation. 

Heat  may  be  evolved  from  air  by  condensation.  This  may  be  shown  by 
placing  a  piece  of  tinder  in.  a  tube,  and  suddenly  compressing  the  air  con- 
tained in  it  by  means  of  a  piston.  The  air  being  thus  condensed,  parts  with 
its  latent  heat  in  sufficient  quantity  to  set  fire  to  the  tinder  at  the  bottom 
of  the  tube. 

Percussion,  which  is  a  combination  of  friction  and  compression,  is  a  familiar 
method  of  developing  heat.  An  example  of  this  is  seen  in  tho  use  of  the 
common  steel  and  flint,  in  which  the  compression  occasioned  by  the  violent 
collision  of  the  two  substances  elicits  heat  sufficient  to  set  fire  to  detached 
portions  of  steel  The  striking  of  iron  with  a  hammer,  or  the  subjection  of 
any  metal  to  great  and  sudden  pressure,  also  develops  large  quantities  of 
heat. 

86.  Chemical  Action  is  the  principal  source  resorted  to 
for  procuring  heat  artificially.      Whenever   this    occurs 
•with  a  high  degree  of  intensity,  heat  is  produced,  accom- 
panied generally  by  an  evolution  of  light.     A  common 
fire,  of  wood  or  coal,  is  a  familiar  illustration  of  the  devel- 
opment of  heat  and  light  by  chemical  action. 

87.  Electricity . — The  passage  of  accumulated  electricity 
through  various  substances,  or  from  one  medium  to  an- 
other, generally  produces  heat.     The  most  intense  arti- 
ficial heat  with  which  we  are  acquainted,  is  thus  produced 
by  the  agency  of  the  electric,  or  galvanic  current.     All 
known  substances  can  be  melted  or  volatilized  by  it. 

Heat  so  developed  has  not  been  employed  for  practical  or  economical  pur- 
poses to  any  great  extent ;  but  for  chemical  experiments  and  investigations 
it  has  been  made  quite  useful. 

88.  Other  Sources  of  Heat, — In  addition  to  the  above- 
mentioned  sources,  some  heat  is  derived  from  the  earth 


the  earth  to  another.  The  store  of  mechanical  force  is  thus  diminished,  and  the  tempe- 
rature of  our  globe  augmented  by  every  tide.  We  do  not,  however,  possess  the  data 
which  -win  enable  us  to  calculate  the  magnitude  of  these  effects. 

QTTESTIONS. — How  may  heat  be  produced  by  condensation  ?  How  by  percussion  ?  What 
is  said  of  chemical  action  as  a  source  of  heat  ?  What  of  electricity  ?  What  other  sources 
of  heat  are  recognized  ? 


COMMUNICATION     OF     HEAT.  63 

itself,  and  from  the  stars  and  planetary  bodies.  Heat, 
also,  is  generated  or  excited  through  the  organs  of  a  liv- 
ing structure,  the  result,  undoubtedly,  of  chemical  actions 
which  are  continually  going  on  in  the  systems  of  animals 
and  plants.  Heat  thus  produced  is  termed  vital,  or  ani- 
mal heat. 

Experimentation  has  also  proved  that  the  simple  act  of  moistening  any 
dry  substance  is  attended  with  slight,  yet  constant  disengagement  of  h<-;it. 
"With  bodies  of  mineral  origin,  when  reduced  to  a  fine  powder  with  a  view  of 
increasing  the  extent  of  surface,  the  rise  of  temperature  does  not  exceed  from 
half  a  degree  to  two  degrees,  Fahrenheit's  thermometer ;  but  with  some  ani- 
mal and  vegetable  substances,  such  as  cotton,  thread,  hair,  wool,  ivory,  and 
well-dried  paper,  a  rise  of  temperature  varying  from  2°  to  even  10°  or  14°  F. 
has  been  observed. 

SECTION    II. 

COMMUNICATION     OF     HEAT. 

89.  Heat   may  be  communicated  in  three  ways  :   by 
CONDUCTION,  by  CONVECTION,  and  by  RADIATION. 

By  one  or  all  of  these  methods,  bodies  which  have  been  heated,  or  cooled, 
gradually  return  to  the  temperature  of  surrounding  objects.  If  the  body  is 
hot.  heat  passes  from  it  to  contiguous  bodies ;  if  cold,  it  gains  heat  at  the 
expense  of  those  substances  which  possess  a  higher  temperature. 

The  three  methods  of  communicating  heat  will  be  considered  in  the  order 
above  named. 

90.  Conduction, — Heat  is  said  to  be  communicated  by 
conduction  when  it  is  transmitted  from  particle  to  particle 
of  a  substance,  as  from  the  end  of  an  iron  bar  placed  in 
the  fire  to  that  part  of  the  bar  most  remote  from  the 
fire. 

Different  bodies  exhibit  a  very  great  degree  of  differ- 
ence in  the  facility  or  power  with  which  they  conduct 
heat  ;  some  substances  oppose  very  little  resistance  to  its 
passage,  while  through  others  it  is  transmitted  slowly,  or 
with  great  difficulty. 


QUESTIONS — How  is  heat  communicated  ?  In  what  way  is  an  equilibrium  of  tempera- 
ture preserved?  What  is  conduction?  Is  the  power  of  conduction  the  same  in  all 
bodies  ? 


64 


PRINCIPLES  OF  CHEMISTRY. 


FIG.  21. 


If  we  place  the  end  of  a  short  rod  of 
glass,  and  of  a  rod  of  iron  of  equal  length, 
in  the  name  of  a  lamp,  Fig.  21,  we  shall 
soon  be  sensible  that  heat  reaches  the  fin- 
gers more  rapidly  through  the  metal  than 
through  the  glass ;  and  shall  have  a  clear 
proof  that    these    two   substances  differ 
greatly  in  their  power  of  conducting  heat. 
The  different  conducting  power  of  va- 
rious solids  may  be  also  strikingly  shown 
by  taking  a  series  of  rods  of  different  materials,  but  of  the  same  dimensions 
(see  Fig.  22),  placing  a  bit  of  wax,  or  phosphorus  upon  one  of  their  extremi- 
ties, and  applying  to  the  other  extremities  an  equal  degree  of  heat.     The  wax 
FIG.  22.  will  melt,   or  the  phosphorus  inflame  at  different 

times,  according  to  the  conducting  power  of  the  dif- 
ferent solids. 

91.  Conductors  and  Non-conductors, 
— All  bodies  are  divided  into  two  classes 
in  respect  to  their  conduction  of  heat, 
viz.,  into  conductors  and  non-conduc- 
tors. The  former  are  such  as  allow 
heat  to  pass. freely  through  them  ;  the 
latter  comprise  those  which  do  not  give 
an  easy  passage  to  it. 
92.  Conductionof  Solids  .*— Of  all  known  substances,  the 
metals  conduct  heat  with  the  greatest  facility  ;  but  they 
differ  considerably  when  compared  with  each  other.  As  a 
general  rule,  the  denser  a  body  is,  the  better  it  conducts 
heat.  Light,  porous  substances,  more  especially  those  of  a 
fibrous  nature,  are  the  worst  conductors  of  heat.  Of  all 
substances,  gold  is  the  best  conductor  of  heat,  and  may 


*  The  following  table  exhibits  the  relative  conducting  power  of  different  substances,  the 
ratio  expressing  the  conducting  power  of  gold  being  taken  at  100 : 


Platinum 

98-10 

Lead                   ,        . 

.  17-96 

Silver 

97-30 

Marble      . 

.     2-34 

Copper 

8^-82 

Porcelain  .        < 

.     1-22 

Iron 

37-41 

Brick  earth 

.    118 

Zinc 

36-3T 

QUESTIONS. — What  experiments  illustrate  this  fact  ?  What  are  conductors  and  non- 
conductors ?  What  are  good  conductors  ?  What  are  bad  conductors  ?  What  substance 
is  the  best  conductor  of  heat  ? 


COMMUNICATION     OF    HEAT. 


65 


be  represented  by  the  number  100  ;  then  iron  will  be 
37.4  ;  marble  2.3  ;  and  brick  clay  1.1. 

The  conducting  power  of  stones  is  next  to  that  of  the 
metals,  and  crystalline  stones  are  better  conductors  than 
those  which  are  not  crystallized. 

93.  Conduction  of  Liquids, — Liquids  conduct  heat  in  a 
very  limited  degree. 

This  may  be  satisfactorily  proved  by  a  number  of  simple  experiments.  If 
a  small  quantity  of  alcohol  be  poured  on  the  surface  of  water  and  inflamed,  it 
will  continue  to  burn  for  some  time.  (See  Fig.  23.)  A  thermometer,  im- 
mersed at  a  small  depth  below  the  common  surface 
of  the  spirit  and  the  water,  will  fail  to  show  any  in- 
crease in  temperature. 

Another  and  more  simple  experiment  proves  the 
same  fact ;  as  whea  a  blacksmith  immerses  his  red- 
hot  iron  in  a  tank  of  water,  the  water  which  sur- 
rounds the  iron  is  made  boiling  hot,  while  the  water 
not  immediately  in  contact  with  it  remains  quite  cold. 

If  a  tube  nearly  filled  with  water  is  held  over  a 
spirit  lamp,  as  in  Fig.  24,  in  such  a  manner  as  to  di- 
rect the  flame  against  the  upper  layers  of  the  water, 
the  water  at  the  top  of  the  tube  may  be  kept  boiling 
for  a  considerable  time,  without  occasioning  the 
slightest  inconvenience  to  the  person  who  holds  it. 

94.  Conduction  of  Gases, — Bodies  in 
the  gaseous,   or  aeriform  condition  are 
conductors  of  heat  than  liquids. 
Common  air,  especially,  is  one  of 

the  worst  conductors  of  heat  with 
which  we  are  acquainted. 

The  non-conducting  properties  of  fibrous 
and  porous  substances  are  due  almost  alto- 
gether to  the  air  contained  in  their  interstices, 
or  between  their  fibers.  These  are  so  dis- 
posed as  to  receive  and  retain  a  large  quantity  of  air  without  permitting  it  to 
circulate. 

Woolens,  furs,  eider-down,  etc.,  are  well  adapted  for  clothing  in  winter,  not 


more  imperfect 
FIG.  24. 


. — How  does  the  conducting  power  of  stones  vary?  What  is  sale!  of  the 
conducting  power  of  liquids?  What  experiments  prove  that  liquids  conduct  heat  imper- 
fectly ?  What  is  the  conducting  power  of  gases  ?  What  of  common  air  ?  Why  are  porous 
and  fihrous  substances  non-conductors?  Why  are  woolens,  furs,  etc.,  well  adapted  for 
clothing  ? 


66  PRINCIPLES     OF     CHEMISTRY. 

because  they  impart  any  heat  to  the  body,  but  on  account  of  the  large  quan- 
tities of  air  which  they  contain,  imprisoned  between  their  fibers ;  this  renders 
them  non-conductors,  and  prevents  the  escape  of  heat  from  the  body. 

Blankets  and  warm  woolen  goods  are  always  made  with  a  nap  or  projec- 
tion of  fibers  upon  the  outside,  in  order  to  take  advantage  of  this  principle. 
The  nap,  or  fibers  retain  air  among  them,  which,  from  its  non-conducting 
properties,  serves  to  increase  the  warmth  of  the  material 

The  heat  generated  in  the  animal  system  by  vital  action  has  constantly  a 
tendency  to  escape,  and  be  dissipated  at  the  surface  of  the  body,  and  the  rate 
at  which  it  is  dissipated  depends  on  the  diiference  between  the  temperature 
of  the  surface  of  the  body  and  the  temperature  of  the  surrounding  medium. 
By  interposing,  however,  a  non-conducting  substance  between  the  surface  of 
the  body  and  the  external  atmosphere,  we  prevent  the  loss  of  heat  which 
would  otherwise  take  place  to  a  greater  or  less  degree. 

An  apartment  is  rendered  much  warmer  for  being  furnished  with  double 
doors  and  windows,  because  the  air  confined  between  the  twro  surfaces  op- 
poses both  the  escape  of  warm  air  out  of  the  room,  and  of  cold  air  into 
the  room. 

Snow  protects  the  soil  in  winter  from  the  effects  of  cold  in  the  same  way 
that  fur  and  wool  protect  animals,  and  clothing  man.  Snow  is  made  up  of  an 
infinite  number  of  little  crystals,  which  retain  among  their  interstices  a  largo 
amount  of  air,  and  thus  contribute  to  render  it  a  non-conductor  of  heat.  A 
covering  of  snow  also  prevents  the  earth  from  throwing  off  its  heat  by  radia- 
tion. The  temperature  of  the  earth,  therefore,  when  covered  with  snow, 
rarely  descends  much  below  the  freezing-point,  even  when  the  air  is  fifteen 
or  twenty  degrees  colder.  Thus  roots  and  fibers  of  trees  and  plants  are 
protected  from  a  destructive  cold. 

As  a  non-conducting  substance  prevents  the  escape  of  heat  from  within  a 
body,  so  it  is  equally  efficacious  in  preventing  the  access  of  heat  from  without. 
In  an  atmosphere  hotter  than  our  bodies,  the  effect  of  clothing  would  be  to 
keep  the  body  cool.  Flannel  is  one  of  the  warmest  articles  of  dress,  yet  we 
can  not  preserve  ice  more  effectually  in  summer  than  by  enveloping  it  in  its 
folds.  Firemen  exposed  to  the  intense  heat  of  furnaces  and  steam-boilers,  in- 
variably protect  themselves  with  flannel  garments. 

Cargoes  of  ice  shipped  to  the  tropics,  are  generally  packed  for  preservation 
in  sawdust ;  a  casing  of  sawdust  is  also  one  of  the  most  effectual  means  of 
preventing  the  escape  of  heat  from  the  surfaces  of  steam-boilers  and  steam- 
pipes.  Straw,  from  its  fibrous  character,  is  an  excellent  non-conductor  of 
heat,  and  is  for  this  reason  extensively  used  by  gardeners  for  incasing  plants 
and  trees  which  are  exposed  to  the  extreme  cold  of  winter. 

Refrigerators,  used  for  the  preservation  of  animal  and  vegetable  substances 
in  warm  weather,  are  double- walled  boxes,  with  the  spaces  between  the  sides 
filled  with  powdered  charcoal,  or  some  other  porous,  non-conducting  substance. 

QUESTIONS.— Why  are  blankets  made  with  a  nap  ?  What  is  the  use  of  clothing?  Why 
do  double  doors  and  windows  render  a  room  warmer  ?  How  does  snow  protect  the  soil  ? 
Why  do  persons  exposed  to  intense  heat  wear  flannel  ?  How  are  refrigerators  constructed  ? 


COMMUNICATION    OF    HEAT. 


67 


The  so-called  "  fire-proof"  safes  are  also  constructed  of  double  or  treble  walls 
of  iron,  with  intervening  spaces  between  them  filled  with  gypsum,  or  "  Plas- 
ter of  Paris."  This  lining,  which  is  a  most  perfect  non-conductor,  prevents 
the  heat  from  passing  from  the  exterior  of  the  safe  to  the  books  and  papers 
within.  The  idea  of  applying  "  Plaster  of  Paris"  in  this  way  for  the  construc- 
tion of  safes,  originated,  in  the  first  instance,  from  a  workman  attempting  to 
heat  water  in  a  tin  basin,  the  bottom  and  sides  of  which  were  thinly  coated 
with  this  substance.  The  non-conducting  properties  of  the  plaster  were  so 
great  as  to  almost  entirely  intercept  the  passage  of  the  heat,  and  the  man, 
to  his  surprise,  found  that  the  water,  although  directly  over  the  fire,  did  not 
get  hot. 

95.  Much  of  the  economy  of  fuel  depends  upon  a  judicious  application  of 
the  principles  which  regulate  the  conduction  of  heat.     An  instructive  illus- 
tration of  their  importance  is  exhibited  in  the  man-  ^        _ 
ner  hi  which  heat  may  be  economized  by  an  appro- 
priate construction  of  steam-boilers.     Thus,  one  of 
the  most  economical  forms,  which  is  known  as  the 
Cornish,  or  cylinder  boiler,  consists  of  two  cylinders, 
placed  one  within  the  other.     (See  Fig.  25.)    Be- 
tween the  two  is  the  space  for  the  water ;  the  inner 
cylinder  contains  the  furnace,  fire-grates,  ash-pit,  and 
the  flue,  or  chamber  through  which  the  products  of 
combustion  pass  off.     By  this  arrangement,  the  heat 
which  would  otherwise  be  conducted  away  by  the 
fire-bars  and  the  masonry  of  the  ash-pit,  is  taken  up  by  the  surrounding 
water,  and  thus  economized.     The 
smoke  and  hot  air  from  the  fire  also'" 
pass  through  the  boiler  for  its  whole 
length,  which  is  sometimes  as  much 
as  forty,  or  even  sixty  feet,  and  then 
return  along  the  outside  of  the  boiler 
through  a  chamber  of  masonry,  be- 
fore they  finally  escape  up  the  chim- 
ney. 

In  the  boiler  of  a  locomotive,  Fig. 
26,  the  fire-box  is  surrounded  at  the 
top  and  two  sides  by  a  double  cas- 
ing containing  water,  and  the  hot  air 
from  the  furnace  passes  through  the 
water  in  the  boiler  in  numerous 
small  parallel  flues,  or  tubes,  which 
open  at  one  end  into  the  fire-box, 
and  at  the  other  into  the  smoke- 


FiG.  26. 


QUESTIONS. — Ho-w  are  safes  rendered  fire-proof  ?    Illustrate  the  application  of  the  prin- 
ciples of  conduction  in  the  construction  of  the  cylinder  boiler.     Also  in  locomotive  boilers. 


68  PKINCIPLES     OF     CHEMISTRY. 

pipe.  By  this  last  arrangement,  the  heat  is,  as  it  were,  filtered  through  the 
water,  and  is  nearly  all  communicated  to  it.  Loss  of  heat  from  the  external 
surfaces  of  locomotive-boilers  may  be  also  prevented  by  casing  them  with 
wood,  or  some  other  non-conducting  substance. 

96.  Convection, — Liquids  and  gases,  being  non-conduc- 
tors, can  not  well  be  beated  like  solids,  by  the  communi- 
cation of  beat  from  particle  to  particle.  Heat,  however, 
is  diffused  through  them  with  great  rapidity  by  a  motion 
of  their  particles,  which  brings  them  successively  in  con- 
tact with  the  heated  surfaces.  This  process  is  termed 
Convection. 

Thus,  when  heat  is  applied  to  the- bottom  of  a  vessel  containing  water,  the 
particles  which  constitute  the  lower  layers  of  liquid  expand  and  become  lighter, 
and  a  double  set  of  currents  is  immediately  established — one  of  hot  particles 
rising  toward  the  surface,  and  the  other  of  colder  particles  descending  to  the 
bottom.  The  portion  of  liquid  which  receives  heat  from  below  is  thus  con- 
tinually diffused  through  the  other  parts,  and  by  this  motion  of  the  particles 
the  heat  is  communicated. 

These  currents  take  place  so  rapidly,  that  if  a  thermom- 

r         j  i 

eter  be  placed  at  the  bottom  and  another  at  the  top  of  a  long 
jar  (the  fire  being  applied  below),  the  upper  one  will  begin 
to  rise  almost  as  soon  as  the  lower  one.  The  circulation  de- 
scribed may  be  rendered  visible,  by  adding  to  a  flask  of 
boiling  water  a  small  quantity  of  bran  or  saw-dust,  or  a  few 
particles  of  bituminous:  coal.  (See  Fig.  27.) 

The  process  of  cooling  in  a  liquid  is  di- 
rectly the  reverse  of  that  of  heating.  The 
particles  at  the  surface,  by  contact  with  the 
air,  readily  lose  their  heat,  become  heavier, 
and  sink,  while  the  warmer  particles  below  in 
turn  rise  to  the  surface. 

To  heat  a  liquid,  therefore,  the  heat  should  be  applied  at  the  bottom  of  the 
mass ;  to  cool  it,  the  cold  should  be  applied  at  the  top,  or  surface. 

The  facility  with  which  a  liquid  may  be  heated  or  cooled,  depends  in  a  great 
degree  on  the  mobility  of  its  particles.  "Water  may  be  made  to  retain  its  heat 
for  a  long  time  by  adding  to  it  a  small  quantity  of  starch,  the  particles  of 
which,  by  their  viscidity  or  tenacity,  prevent  the  free  circulation  of  the  heated 
particles  of  water.  For  the  same  reason  soup  retains  its  heat  longer  than 
water,  and  all  thick  liquids,  like  oil,  molasses,  tar,  etc.,  require  a  considerable 
time  for  cooling. 

QUESTIONS. —What  is  convection  ?  Illustrate  the  communication  of  heat  by  convection. 
Explain  the  process  of  cooling  in  liquid*  What  circumstance  greatly  influences  the  heat- 
ing and  cooling  of  liquids  ? 


COMMUNICATION     OF     HEAT.  69 

97.  Heating  of  Gases  and  Vapors,— Common  air,  and  all 
gases  and  vapors,  are  heated  in  the  same  manner  as  liquids. 
From  every  heated  substance,  an  upward  current  of  air  is 
continually  rising. 

It  is  in  accordance  with  this  principle  that  we  are  enabled  to  readily  warm 
the  air  of  an  apartment  by  means  of  a  stove,  or  furnace.  The  air  in  immediate 
contact  with  the  hot  surface  becomes  heated  and  rises,  while  cooler  and 
heavier  air  rushes  in  from  all  sides  to  supply  its  place.  This,  in  turn,  becomes 
heated  and  ascends,  and  thua  a  circulation  similar  to  that  which  occurs  in  a 
flask  of  boiling  water,  is  established. 

98.  Winds  and  Ocean  Currents, — The  processes  of  circu- 
lation produced  by  heat  in  liquids  and  in  gases,  which 
have  been  described,  occur  upon  a  vast  scale  in  the  atmos- 
phere and  in  the  ocean. 

Aerial  currents  are  most  powerful  at  the  equator,  the  warm  air  of  which  rises 
and  incessantly  flows  in  the  upper  regions  of  the  atmosphere  toward  the 
poles ;  while  just  as  constantly,  at  the  earth's  surface,  currents  of  cool  air, 
constituting  the  trade  winds,  flow  from  the  poles  to  the  equator. 

Similar  currents  are  produced  by  the  same  cause  in  the  waters  of  the 
ocean.  Their  power  may  be  inferred  from  the  influences  which  hi  some  cases 
they  exert  upon  climate.  By  them  the  warm  water  of  the  Gulf  of  Mexico 
is  carried  to  the  British  Isles,  thereby  producing  a  mild,  uniform  warmth, 
and  a  rich  moisture ;  while  through  similar  causes,  the  floating  ice  of  the 
North  Pole  is  carried  to  the  coast  of  Newfoundland,  and  produces  cold.* 

99.  Radiation,— When  the  hand  is  placed  near  a  hot 
body  suspended  in  the  air,  a  sensation  of  warmth  is  per- 
ceived, even  for  a  considerable  distance.     If  the  hand  be 
held  beneath  the  body,  the  sensation  will  be  as  great  as 
upon .  the  sides,   although   the  heat  has  to  shoot  down 
through  an  opposing  current  of  air  approaching  it.     This 
effect  does  not  arise  from  the  heat  being  conveyed  by 


*  Further,  by  the  heat  of  the  sun  a  portion  of  the  water  is  converted  into  vapor,  which 
rises  in  the  atmosphere,  is  condensed  into  clouds,  or  falls  as  rain  or  snow  upon  the  earth ; 
collects  in  the  form  of  springs,  brooks,  and  rivers ;  and  finally  reaches  the  sea  again,  after 
having  gnawed  the  rocks,  carried  away  the  light  earth,  and  thus  performed  its  part  in  the 
geologic  changes  of  the  earth  ;  perhaps,  beside  all  this,  it  has  driven  our  water-mill  on' 
Its  way.  If  the  heat  of  the  sun  were  withdrawn,  there  would  remain  only  a  single  mo- 
tion of  water  (provided  it  remained  a  liquid),  namely,  the  tides,  which  are  produced  by 
the  attraction  of  the  sun  and  moon. 

QUESTIONS. — How  are  gases  and  vapors  heated?  Upon  what  principle  are  rooms 
warmed  by  stoves  and  furnaces  ?  What  is  tho  occasion  of  winds  and  ocean  currents? 
Define  radiation. 


70  PKIKCIPLES     OF     CHEMISTRY. 

means  of  a  hot  current,  since  all  the  heated  particles  have 
a  uniform  tendency  to  rise  ;  neither  can  it  depend  upon 
the  conducting  power  of  the  air,  because  aeriform  sub- 
stances possess  that  power  in  a  very  low  degree,  while  the 
sensation  in  the  present  case  is  excited  almost  on  the  in- 
stant. This  method  of  distributing  heat,  to  distinguish  it 
from  heat  passing  by  conduction,  or  convection,  is  called 
radiation,  and  heat  thus  distributed  is  termed  radiant,  or 
radiated  heat. 

Heat  is  communicated  through  space  by  radiation  in 
straight  lines,  and  its  intensity  diminishes  as  the  square  of 
the  distance  from  the  center  of  action  increases. 

Thus  the  heating  effect  of  any  hot  body  is  nine  times  less  at  three  feet 
than  at  one ;  sixteen  times  less  at  four  feet ;  and  twenty-five  times  less  at 
five. 

All  bodies  radiate  heat  in  some  measure,  but  not  all 
equally  well ;  radiation  being  generally  in  proportion  to 
the  roughness  of  the  radiating  surface.  All  dull  and  dark 
substances  are,  for  the  most  part,  good  radiators  of  heat ; 
but  bright  and  polished  substances  are  generally  bad 
radiators.  Color,  however,  alone,  has  no  effect  on  the 
radiation  of  heat. 

A  liquid  contained  in  a  bright,  highly -polished  metal  pot,  will  retain  its 
heat  much  longer  than  in  a  dull  and  blackened  one.  This  is  not  due  to  the 
polish  or  brightness  of  the  surface,  but  to  the  fact  that,  by  polishing,  the  sur? 
face  is  rendered  dense  and  smooth,  and  such  surfaces  do  not  allow  the  heat  to 
escape  readily.  If  we  cover  the  polished  metal  surface  with  a  thin  cotton  or 
linen  cloth,  so  as  to  render  the  surface  less  dense,  the  radiation  of  heat,  and 
consequent  cooling,  will  proceed  rapidly. 

Black  lead  is  one  of  the  best  known  radiators  of  heat,  and  on  this  account 
is  generally  employed  for  the  blackening  of  stoves  and  hot-air  flues.  As  a 
high  polish  is  unfavorable  to  radiation,  stoves  should  not  be  too  highly  polished 
with  this  substance. 

The  great  supply  of  heat  to  the  earth  from  the  sun  is  transmitted  by  the 
process  of  radiation.  Some  idea  of  the  amount  of  heat  thus  received  by  the 
earth  may  be  formed  from  a  calculation  of  Professor  Faraday,  which  indicated 
that  the  average  amount  of  heat  radiated  in  a  summer's  day  upon  each  acre 


QUESTIONS. — Ho-wis  heat  communicated  by  radiation  1  What  circumstances  influence 
radiation  ?  What  are  good  and  bad  radiators  1  "What  amount  of  heat  does  the  earth  re- 
ceive by  radiation  from  the  sun  1 


COMMUNICATION     OF     HEAT.  71 

of  land  iu  the  latitude  of  London,  is  not  less  than  that  which  would  be  pro- 
duced by  the  combustion  of  18,000  pounds  of  coal. 

The  radiation  of  heat  goes  on  at  all  times,  and  from  all 
surfaces,  whether  their  temperature  be  the  same  as,  or  dif- 
ferent from  that  of  surrounding  objects ;  therefore  the 
temperature  of  a  body  falls  when  it  radiates  more  heat 
than  it  absorbs  ;  its  temperature  is  stationary  when  the 
quantities  emitted  and  received  are  equal ;  and  it  grows 
warm  when  the  absorption  exceeds  the  radiation. 

If  a  body,  at  any  temperature,  be  placed  among  other  bodies,  it  will  affect 
their  condition  of  temperature,  or  as  we  express  it,  it  will  affect  them  ther- 
mally ;  just  as  a  candle  brought  into  a  room  illuminates  all  bodies  in  its  pres- 
ence ;  with  this  difference,  however,  that  if  the  candle  be  extinguished,  no 
more  light  is  diffused  by  it ;  but  no  body  can  be  thermally  extinguished.  All 
bodies,  however  low  be  their  temperature,  contain  heat,  and  therefore  radiate 
it. 

If  a  piece  of  ice  be  held  before  a  thermometer,  it  will  cause  the  mercury  in 
its  tube  to  fall,  and  hence  it  has  been  supposed  that  the  ice  emitted  rays  of 
cold.  This  supposition  is  erroneous.  The  ice  and  the  thermometer  both 
radiate  heat,  and  each  absorbs  more  or  less  of  what  the  other  radiates  toward 
it.  But  the  ice,  being  at  a  lower  temperature  than  the  thermometer,  radiates 
less  than  the  thermometer,  and  therefore  the  thermometer  "absorbs  less  than 
the  ice,  and  consequently  falls.  If  the  thermometer  placed  in  the  presence 
of  the  ice  had  been  at  a  lower  temperature  than  the  ice,  it  would,  for  liko 
reasons,  have  risen.  The  ice  in  that  case  would  have  wanned  the  ther- 
mometer. 

100.  Disposition  of  Radiant  Heat. — When  rays  of  heat 
radiated  from  one  body  fall  upon  the  surface  of  another 
body,  they  may  be  disposed  of  in  three  ways  :  1.  They 
may  rebound  from  its  surface,  or  be  reflected  ;  2.  They 
may  be  received  into  its  surface,  or  be  absorbed  ;  3.  They 
may  pass  directly  through  the  substance  of  the  body,  or 
be  transmitted. 

101.  Reflection  of  Heat, — Polished  metallic  surfaces  con- 
stitute the  best  reflectors  of  heat ;  but  all  bright  and  light 
colored  surfaces  are  adapted  for  this  purpose  to  a  greater, 
or  less  degree. 

"Water  requires  a  longer  time  to  become  hot  in  a  bright  tin  vessel  than  in  a 

QUESTIONS.— Does  radiation  proceed  constantly  from  all  bodies  ?  Why  does  the  mer- 
cury of  a  thermometer  sink  when  brought  near  ice  ?  When  radiant  heat  falls  upon  the 
surface  of  a  body,  how  may  it  be  disposed  of?  What  surfaces  are  good  reflectors  of  heat? 


72  PRINCIPLES     OF     CHEMISTRY. 

dark  colored  one,  because  the  heat  is  reflected  from  the  bright  surface,  and 
does  not  enter  the  vessel. 

The  power  of  reflection  of  heat  seems  to  reside  almost  exclusively  in  the 
surface.  A  film  of  gold  leaf,  not  exceeding  l-200,000th  of  an  inch  in  thick- 
ness, answers  the  purpose  of  a  reflector  nearly  as  well  as  a  mass  of  solid  gold. 

102.  Absorption  of  Heat.— The  power  of  absorbing  heat 
varies  with  almost  every  form  of  matter.     Surfaces  are 
good  absorbers  of  heat  in  proportion  as  they  are  poor  re- 
flectors.    The  best  radiators  of  heat  also  are  the  most  pow- 
erful absorbers,  and  the  most  imperfect  reflectors. 

Dark  colors  absorb  heat  from  the  sun  more  abundantly  than  light  ones. 
This  may  be  proved  by  placing  a  piece  of  black  and  a  piece  of  white  cloth 
upon  the  snow  exposed  to  the  sun ;  in  a  few  hours  the  black  cloth  will  have 
melted  the  snow  beneath  it,  while  the  white  cloth  will  have  produced  little 
or  no  effect  upon  it. 

A  piece  of  brown  paper  submitted  to  tho  action  of  a  burning-glass,  ignites 
much  more  quickly  than  a  piece  of  white  paper.  The  reason  of  this  is,  that 
the  white  paper  reflects  the  rays  of  the  sun,  and  though  but  slightly  heated 
appears  highly  luminous;  while  the  brown  paper  which  absorbs  the  rays, 
readily  becomes  heated  to  ignition.  For  the  same  reason  a  kettle  whose  bot- 
tom and  sides  are  covered  with  soot,  heats  water  more  readily  than  a  kettle 
whose  sides  are  bright  and  clean. 

Ah*  absorbs  heat  very  slowly,  and  does  not  readily  part  with  it.  Air  is  not 
heated  to  any  extent  by  the  direct  rays  of  the  sun.  The  sun,  however,  heats 
the  surface  of  the  earth,  and  the  air  resting  upon  it  is  heated  by  contact  with 
it,  and  ascends,  its  place  being  supplied  by  colder  portions,  which  in  turn  are 
heated  also. 

This  reluctance  of  air  to  part  with  its  heat  occasions  some  very  curious  dif- 
ferences between  its  burning  temperature  and  that  of  other  bodies.  Metals, 
which  are  generally  the  best  conductors,  and  therefore  communicate  heat 
most  readily,  can  not  be  handled  with  impunity  when  raised  to  a  temperature 
of  more  than  120°  F. ;  water  becomes  scalding  hot  at  150°  F. ;  but  air  ap- 
plied to  the  skin  occasions  no  very  painful  sensation  when  its  heat  is  far  be- 
yond that  of  boiling  water. 

103.  Formation  of  Dew, — Dew  is  the  moisture  of  the 
air  condensed  by  coming  in  contact  with  bodies  colder 
than  itself. 

As  soon  as  the  sun  has  set  in  summer,  and  the  earth  is  no  longer  receiving 
new  supplies  of  heat,  its  surface  begins  to  throw  off  the  heat  (which  it  has 

QUESTIONS.— Where  does  the  power  of  reflecting  heat  reside  in  solid  bodies  ?  How- 
does  the  power  of  absorbing  heat  vary  in  different  substances  ?  What  are  good  absorbers 
of  heat?  What  are  the  peculiarities  of  air  as  respects  absorption  of  heat?  How  is  the 
atmosphere  heated?  What  curious  experiments  illustrate  the  retention  of  heat  by  the 
air  ?  What  is  dew  ?  To  what  is  the  formation  of  dew  owing  ? 


COMMUNICATION    OF    HEAT.  73 

accumulated  during  the  day)  by  radiation ;  the  air,  however,  does  not  radiate 
its  heat,  and,  in  consequence,  the  different  objects  upon  the  earth's  surface 
are  soon  cooled  down  from  7  to  25  degrees  below  the  temperature  of  the  sur- 
rounding atmosphere.  The  warm  vapor  of  the  air,  coming  in  contact  with 
these  cool  bodies,  is  condensed  and  precipitated  as  dew. 

All  bodies  have  not  an  equal  capacity  for  radiating  heat,  but  some  cool 
much  more  rapidly  and  perfectly  than  others.  Hence  it  follows,  that  with 
the  same  exposure,  some  bodies  will  be  densely  covered  with  dew,  while 
others  will  remain  perfectly  dry.  Grass,  the  leaves  of  trees,  wood,  eta,  radiate 
heat  very  freely ;  but  polished  metals,  smooth  stones,  and  woolen  cloth,  part 
with  their  heat  slowly:  the  former  of  these  substances  will  therefore  be  com- 
pletely drenched  with  dew,  while-  the  latter,  in  the  same  situations,  will  be 
almost  dry. 

The  surfaces  of  rocks  and  barren  lands  are  so  compact  and  hard,  that  they 
can  neither  absorb  nor  radiate  much  heat  •  and  (as  their  temperature  varies 
but  slightly)  little  dew  is  deposited  upon  them.  Cultivated  soils,  on  the 
contrary  (being  loose  and  porous)  very  freely  radiate  by  night  the  heat  which 
they  absorb  by  day ;  in  consequence  of  which  they  are  much  cooled  down, 
and  plentifully  condense  the  vapor  of  the  air  into  dew.  Such  a  condition 
of  things  is  a  remarkable  evidence  of  design  on  the  part  of  the  Creator,  since 
every  plant  and  inch  of  land  which  needs  the  moisture  of  dew  is  adapted  to 
collect  it;  but  not  a  single  drop  is  wasted  where  its  refreshing  moisture  is  not 
required. 

Dew  is  always  formed  upon  the  surface  of  the  material 
upon  which  it  is  found,  and  does  not  fall  from  the  atmos- 
phere. 

104.  Frost  is  frozen  dew.     When  the  temperature  of 
the  body  upon  which  the  dew  is  deposited  sinks  below  32° 
F.j  the  moisture  freezes  and  assumes  a  solid  form,  consti- 
tuting what  is  called  "frost." 

105.  Dew-Point, — The  temperature  at  which  the  con- 
densation of  moisture  in  the  atmosphere  commences,  or 
the  degree  indicated  by  the  thermometer  at  which  dew 
begins  to  be  deposited,  is  called  the  "  I)ew-rPoint." 

This  point  is  by  no  means  constant  or  invariable,  since  dew  is  only  de- 
posited when  the  air  is  saturated  with  vapor,  and  the  amount  of  moisture  re- 
quired to  saturate  air  of  high  temperature  is  much  greater  than  for  air  of 
low  temperature. 

If  the  saturation  be  complete,  the  least  diminution  of  temperature  is  at- 
tended with  the  formation  of  dew  j  but  if  the  air  is  dry,  a  body  must  be 

QUESTIONS.— Is  dew  deposited  equally  upon  all  substances  ?  Does  dew  fall  ?  What  is 
frost  ?  What  is  the  dew-point  ? 

4 


74  PRINCIPLES     OF     CHEMISTRY. 

several  degrees  colder  before  moisture  is  deposited  on  its  surface ;  and  indeed 
the  drier  the  atmosphere,  the  greater  will  be  the  difference  between  the  tem- 
perature and  its  dew-point. 

Dew  may  be  produced  at  any  time  by  bringing  a  vessel  of  cold  water  into 
a  warm  room.  The  sides  of  the  vessel  cool  the  surrounding  air  to  such  an 
extent  that  it  can  no  longer  retain  all  its  vapor,  or,  in  other,  words,  the  tem- 
perature of  the  air  contiguous  to  the  cold  surface  is  reduced  below  the  dew- 
point  ;  dew  therefore  forms  upon  the  vessel.  A  pitcher  of  water  under  such 
circumstances  is  vulgarly  said  to  £;  sweat." 

106.  Transmission  of  Heat,— Heat  derived  from  the 
sun,  like  light  emanating  from  the  same  source,  passes 
through  all  transparent  bodies,  without  material  loss- ; 
but  heat  derived  from  terrestrial  and  less  intense  sources, 
is  in  great  part  arrested  by  many  substances,  which  allow 
light  to  pass  freely. 

Thus,  a  plate  of  glass  held  between  one's  face  and  the  sun  will  not  protect 
it,  but  held  between  the  face  and  a  fire,  it  will  intercept  a  large  proportion  of 
the  heat. 

The  power  of  heat  to  penetrate  a  dense  transparent 
substance  increases  in  proportion  as  the  temperature  of 
the  body  from  which  it  is  radiated  increases. 

Rock-salt  appears  to  be  the  only  substance  which  transmits  an  equal 
amount  of  heat  from  all  sources.  It  has,  hence,  been  called  the  "glass  of 
heat,"  since  it  permits  heat  to  pass  with  the  same  ease  that  glass  does  light. 
Alum,  on  the  contrary,  which  is  nearly  transparent,  almost  entirely  intercepts 
the  passage  of  terrestrial  heat.  Heat,  indeed,  will  pass  more  readily  through 
a  black  glass,  so  dark  that  the  sun  at  noonday  is  scarcely  discernible  through 
it,  than  through  a  thin  plate  of  clear  alum. 

Transparent  substances  of  considerable  density,  such  as  glass,  alum,  water, 
rock-crystal,  etc.,  interfere  most  with  the  passage  of  heat ;  while  transparent 
substances  of  little  density,  as  air,  the  various  gases,  etc.,  allow  heat  to  pass 
with  comparatively  little  interruption. 

Those  substances  which  transmit  heat  most  freely,  are 
termed  diathermanous  ;  and  those  which  intercept  the 
rays  of  heat  more  or  less  completely,  atliermanous. 

QUESTIONS. — State  the  peculiarities  which  distinguish  the  transmission  of  heat  derived 
from  different  sources  ?  Upon  what  does  the  power  of  heat  to  penetrate  a  substance  de- 
pend? What  substance  transmits  heat  most  readily?  What  least  so?  What  terms 
have  been  used  to  indicate  the  difference  in  bodies  as  respects  the  transmission  of  heat  ? 


THE     EFFECTS     OF    HEAT.  75 

SECTION    III. 

THE    EFFECTS    OF    HEAT. 

107.  Universal  Influence  of  Heat —The    form    of   all 
bodies  appears  to  be  materially  affected  bj  heat ;  by  its 
increase  solids  are  converted  into  liquids,  and  liquids  into 
vapor  ;  by  its  diminution  vapors  are  condensed  into  liquids, 
and  these  in  turn  become  solids. 

If  matter  ceased  to  be  influenced  by  heat,  all  liquids,  vapors,  and  doubtless 
even  gases,  would  become  permanently  solid,  and  all  motion  on  the  surface 
of  the  earth  would  be  arrested. 

108.  Specific  Heat, — All  bodies    contain    incorporated 
with  them  more  or  less  of  heat ;  but  equal  weights  of  dis- 
similar substances  require  unequal  quantities  of  heat  to 
elevate  them  to  the  same  temperature. 

Thus,  if  we  place  a  pound  of  water  and  a  pound  of  mercury  over  a  fire,  it 
will  be  found  that  the  mercury  will  attain  to  any  given  temperature  much 
quicker  than  the  water.  Or  if  we  perform  the  converse  of  this  experiment, 
and  take  two  equal  quantities  of  mercury  and  water,  and  having  heated  them 
to  the  same  degree  of  temperature,  allow  them  to  cool  freely  in  the  air,  it  will 
be  found  that  the  water  will  require  much  more  time  to  cool  down  to  a  com- 
mon temperature  than  the  mercury.  The  water  obviously  contains  more  heat 
at  the  elevated  temperature  than  the  mercury,  and  therefore  requires  a  longer 
time  to  cool. 

Dissimilar  substances  require,  respectively,  different 
quantities  of  heat  to  raise  their  temperature  one  degree  ; 
and  the  quantity  of  heat  required  to  raise  any  substance 
one  degree  in  temperature,  as  compared  with  the  quantity 
required  to  raise  an  equal  weight  of  some  other  substance, 
selected  as  a  standard  of  comparison,  one  degree,  is  called 
its  specific  heat.  In  like  manner,  the  weight  which  a 
body  includes  under  a  given  volume,  is  termed  its  specific 
weight.  Water  is  adopted  as  the  standard  for  comparing 
the  different  quantities  of  heat  which  equal  weights  of 
dissimilar  substances  contain. 

QUESTIONS.— What  is  said  respecting  the  universal  influence  of  heat?  Is  the  same 
amount  of  heat  contained  in  all  substances  ?  What  experiment  proves  that  water  contains 
mo  re  heat  than  mercury?  What  is  specific  heat?  What  standard  is  adopted  for  com- 
paring the  heat  of  different  substances? 


76  PKINCIPLES    OF    CHEMISTRY. 

109.  Capacity  for  Heat, — A  substance  is  said  to  have  a 
greater,  or  less  capacity  for  heat,  according  as  a  greater, 
or  less  quantity  of  heat  is  required  to  produce  a  definite 
change  of  temperature,  or  an  elevation  of  temperature  of 
one  degree. 

In  general,  the  capacity  of  bodies  for  heat  decreases  with  their  density. 
Thus  mercury  has  a  less  capacity  for  heat  than  water,  because  its  density  is 
greater.  Air  that  is  rarefied,  or  thin,  has  a  greater  capacity  for  heat  than 
dense  air.  This  circumstance  will  explain,  in  part,  the  reason  of  the  very  low 
temperatures  which  exist  at  great  elevations  in  the  atmosphere.  Persons 
ascending  high  mountains,  or  in  balloons,  find  that  the  cold  increases  with 
the  elevation.  The  reason  of  this  is,  that  the  air  in  the  upper  regions  of  tho 
atmosphere,  relieved  from  superincumbent  pressure,  is  expanded  and  rarefied  ; 
its  capacity  for  heat  is,  therefore,  greatly  increased,  and  it  absorbs  Its  own 
sensible  heat.' 

In  all  quarters  of  the  globe,  the  temperature  of  the  air  at  a  certain  height 
is  reduced  so  low  by  its  rarefaction,  that  water  can  not  exist  in  a  liquid  state. 
This  limit,  the  height  of  which  varies,  being  the  most  elevated  at  the  equator, 
and  the  most  depressed  at  the  poles,  is  called  the  line  of  PERPETUAL  SNOW.* 

If  compressed  air  be  allowed  suddenly  to  expand,  by  escaping  into  the  at- 
mosphere, the  rarefaction  produced  increases  its  capacity  for  heat ;  it,  there- 
fore, absorbs  heat  most  readily,  and  occasions  a  sensation  of  cold.  It  is  on 
this  account  that  air  forcibly  expelled  from  the  mouth  feels  cool. 

On  the  contra^,  if  we  compress  a  quantity  of  air,  and  render  it  more  dense, 
we  diminish  its  capacity  for  heat,  and  it  becomes  incapable  of  retaining  what 
Was  before  incorporated  into  its  substance.  The  proof  of  this  may  be  found 
in  the  fact,  that  by  the  sudden  compression  of  a  small  quantity  of  air  in  a 
suitable  vessel  we  may  obtain  a  sufficient  amount  of  heat  to  ignite  tinder  and 
other  inflammable  substances. 

The  capacity  for  heat  increases  with  the  'temperature. 
Thus  it  requires  a  greater  amount  of  heat  to  elevate  the 
temperature  of  platinum  from  212°  to  213°,  than  from 
32°  to  33°. 

A  body  in  a  liquid  state  has  a  higher  specific  heat 
than  the  same  substance  when  it  is  in  the  solid  form. 


*  The  line  of  perpetual  snow  at  the  equator  occurs  at  a  height  of  about  15,000  feet ;  at 
the  Straits  of  Magellan,  it  occurs  at  an  elevation  of  only  4,000  feet. 


QUESTIONS. — What  is  understood  by  capacitj'  for  heat?  How  does  the  capacity  of 
bodies  for  heat  increase  ?  Why  is  the  temperature  of  air  at  high  elevations  very  much 
reduced  ?  Why  does  the  compression  of  air  produce  heat  ?  How  does  the  capacity  for 
heat  vary  with  the  temperature  ? 


THE     EFFECTS     OF     HEAT.  77 

This  is  remarkably  shown  in  the  case  of  water,  the  specific 
heat  of  which  is  double  that  of  ice. 

Of  all  known  substances,  water  has  the  greatest  capacity  for  heat.  This 
circumstance  renders  the  ocean  a  great  reservoir  of  heat,  and  a  regulator  of 
temperatures  upon  the  surface  of  the  earth.  Thus  in  hot  weather,  the  water 
of  the  ocean,  on  account  of  its  great  capacity  for  heat,  absorbs  and  retains 
large  quantities  from  the  air ;  the  air,  therefore,  accumulates  heat  but  slowly. 
In  cold  weather,  the  heat  previously  absorbed  by  the  ocean  is  gradually  re- 
stored to  the  air,  and  a  sudden  reduction  of  atmospheric  temperature  is  pre- 
vented. It  is,  therefore,  mainly  on  this  account  that  sea-coasts  and  islands 
enjoy  a  more  uniform  temperature  than  the  interior  of  continents.  In  the 
summer,  the  proximity  of  tho  sea  serves  to  mitigate  the  heat;  in  the  winter, 
to  diminish  the  cold.  Inland  lakes,  in  like  manner,  raise  the  mean  tempera- 
ture. The  climate  of  the  shores  of  Lake  Erie  is  much  milder  than  that  of  the 
adjacent  inland  country,  and  fruit  may  bo  successfully  cultivated  at  Cleveland, 
upon  the  southern  shore,  which  fails  to  ripen  in  districts  further  south. 

An  ocean  of  mercury  would  produce  very  different  results,  since  it  is  ca- 
pable of  absorbing  but  a  small  amount  of  heat,  which  it  readily  parts  with  at 
a  slight  reduction  of  temperature. 

.110.  Cal-o  rim'e-try,— The  art  of  determining  the  spe- 
cific heat  of  various  substances  is  called  Calorimetry. 

Several  different  methods  may  be  employed  for  this  purpose.  One  method 
consists  in  inclosing  equal  weights  of  different  substances,  heated  to  the  same 
temperature,  in  closed  cavities  in  a  block  of  ice,  and  measuring  the  respective 
quantities  of  water  which  they  produce  by  melting  the  ice. 

The  same  result  may  also  be  obtained  by  what  is  called  the  method  of  mix- 
tures. Thus,  if  we  mix  1  pound  of  mercury  at  66°  with  1  pound  of  water 
at  32°,  the  common  temperature  will  be  33°.  Here  the  mercury  loses  33° 
and  the  water  gains  1° ;  that  is  to  say,  the  33°  of  the  mercury  only  elevates 
the  water  1°,  therefore  the  capacity  of  water  for  heat  is  33  times  that  of 
mercury ;  or,  if  we  call  the  capacity  or  specific  heat  of  water  1,  then  the  capacity, 
or  specific  heat  of  mercury,  as  compared  with  water,  will  be  l-33d,  or  .333. 

In  this  way  the  specific  heat  of  a  great  number  of  bodies  has  been  deter- 
mined, and  tables  constructed  in  which  they  are  recorded. 

111.  Apparent  Effects  of  Heat,— The  three  most  appa- 
rent effects  of  heat,  so  far  as  they  relate  to  the  form  and 
dimensions  of  bodies,  are  Expansion,  Liquefaction,  and 
Vaporization. 

112.  Theory  of  Expansion, — Heat  operates  to  produce 

QUESTIONS.— What  substance  has  the  greatest  capacity  for  heat  ?  How  do  great  bodies 
of  -water  serve  to  regulate  temperature  ?  What  is  caloriraetry  ?  How  is  the  specific  heat 
of  bodies  determined?  What  are  the  three  most  apparent  effects  of  heat?  How  does 
heat  produce  expansion  ? 


T8  PRINCIPLES     OF     CHEMISTRY. 

expansion  by  introducing  a  repulsive  force  among  the 
particles  of  the  body  it  pervades.  This  repulsive  force 
gives  to  the  particles  a  tendency  to  separate,  or  increase 
their  distance  from  one  another.  Hence  the  general  mass 
of  the  body  is  made  to  occupy  a  larger  space,  or  expand. 

The  expansion  occasioned  by  heat  is  greatest  in  those 
bodies  which  are  the  least  influenced  by  cohesion.  Solids 
expand  less  for  equal  elevations  of  temperature  than 
either  liquids  or  gases. 

The  expansion  of  the  same  body  will  continue  to  in- 
crease with  the  quantity  of  heat  that  enters  it,  so  long 
as  the  form  and  chemical  constitution  of  the  body  is  pre- 
served. 

113.  Expansion  of  Solids,— Solids  appear  to  expand  uni- 
formly from  the  freezing  point  of  water  up  to  212°,  the 
boiling  point  of  water ; — that  is  to  say,  the  increase  of 
volume  which  attends  each  degree  of  temperature  which 
the  body  receives  is  equal.  When  solids  are  elevated, 
however,  to  temperatures  above  212°,  they  do  not  dilate 
uniformly,  but  expand  in  an  increasing  ratio. 

Different  solids,  however,  expand  very  unequally  for 
equal  additions  of  temperature. 

Among  solids  the  metals  expand  the  most ;  but  an  iron  wire  increases  only 
p         .  1-802  in  bulk  when  heated  from  zero  of  the 

thermometer  up  to  212°.  Zinc  is  the  most 
expansible  of  the  metals,  and  platinum  the 
most  uniform  in  its  rate  of  expansion  at  all 
temperatures.  Wood  and  marble  expand 
but  slightly. 

The  expansion  of  solids  by  heat  is  clearly 
shown  by  the  following  experiment,  Fig. 
28.  m  represents  a  ring  of  metal,  through 
which,  at  the  ordinary  temperature,  a  small 
iron  or  copper  ball,  a,  will  pass  freely,  this 
ball  being  a  little  less  than  the  diameter  of 
the  ring.  If  this  ball  be  now  heated  by  the 

flame  of  an  alcohol  lamp,  it  will  expand  by  heat  to  such  an  extent  as  no 

longer  to  pass  through  the  ring. 

QUESTIONS. — What  bodies  expand  most  under  the  influence  of  heat  ?  Is  the  expansion 
of  bodies  by  heat  limited  ?  What  is  the  law  of  expansion  for  solids  ? 


THE     EFFECTS     OF     HEAT.  79 

Bodies,  in  general,  expanded  under  the  influence  of 
heat,  return  to  their  original  dimensions  in  cooling. 

Lead,  however,  is  an  exception  to  this  rule.  From  its  extreme  softness, 
its  particles  slide  over  each  other  in  the  act  of  expansion,  and  do  not  return 
to  their  original  position,  "  A  leaden  pipe,  used  for  conveying  steam,  perma- 
nently lengthens  some  inches  in  a  short  time,  and  the  leaden  flooring  of  a 
sink,  which  often  receives  hot  water,  becomes,  in  the  course  of  use,  thrown 
up  into  ridges  and  puckers." 

114.  Force  t)f  Expansion,— The  force  with  which  bodies 
expand  and  contract  under  the  influence  of  the  increase 
or  diminution  of  heat,  is  apparently  irresistible,  and  is  re- 
cognized as  one  of  the  greatest  forces  in  nature. 

The  amount  of  force  with  which  a  solid  body  will  ex- 
pand or  contract  through  the  influence  of  heat,  is  equal 
to  that  which  would  be  required  to  compress  it  by  me- 
chanical means  through  a  space  equal  to  its  expansion,  or 
elongate  it  through  a  space  equal  to  its  contraction. 

A  bar  of  malleable  iron,  having  a  section  of  a  square  inch,  is  stretched 
1-10, 000th  of  its  length  by  a  ton  weight ;  a  similar  elongation  is  produced  by 
the  influence  of  about  sixteen  degrees  of  heat,  Fahrenheit  In  this  climate,  a 
variation  of  80°  F.  between  the  cold  of  winter  and  the  heat  of  summer  not 
^infrequently  takes  place.  Within  these  limits,  a  brought  iron  bar  ten  inches 
long  will  vary  in  length  5-1, 000th  of  an  inch;  and  is  capable  of  exerting  a 
strain  of  fifty  tons  upon  a  square  inch. 

Experiments  made  a  few  years  since  demonstrated,  that 
Bunker  Hill  monument  is  caused  to  vary  each  day  from 
a  vertical  position,  by  the  heat  of  the  sun  expanding  un- 
equally the  granite  of  which  it  is  constructed. 

The  expansion  of  solids  by  heat  is  made  applicable  for  many  useful  pur- 
poses in  the  arts.  The  tires  of  wheels,  and  hoops  surrounding  water-vats, 
barrels,  etc.,  are  made  in  the  first  instance  somewhat  smaller  than  the  frame- 
Nvork  they  are  intended  to  surround.  They  are  then  heated  red  hot  and  put 
on  in  an  expanded  condition.;  on  cooling,  they  contract  and  bind  together  the 
several  parts  with  a  greater  force  than  could  be  conveniently  applied  by  any 
mechanical  means.  In  like  manner,  in  constructing  steam-boilers,  the  rivets 
are  fastened  while  hot,  in  order  that  they  may,  by  subsequent  contraction, 
bind  the  plates  together  more  firmly. 

In  many  operations,  however,  the  force  of  expansion  requires  to  be  care- 

QITEBTIONS. — Is  expansion  by  heat  counteracted  by  cooling?  With  what  force  do  bodies 
expand  and  contract  by  the  increase,  or  diminution  of  heat  ?  Mention  some  instances  of 
expansion  in  the  arts  ?  In  what  cases  is  it  necessary  to  guard  against  the  expansion  of 
solids? 


80  PRINCIPLES     OF     CHEMISTRY. 

fully  guarded  against.  This  is  especially  the  case  when  iron  is  combined  in 
any  structure  with  less,  expansible  materials- 
Iron  clamps  and  bars,  built  into  walls  of  masonry,,  frequently  weaken,  or 
destroy,  by  their  expansion  and  contraction,  the  structure  they  were  intended 
to  support.  Iron  pipes  used  for  the  conveyance  of  steam  or  hot  water,  should 
not  be  allowed  to  abut  against  a  wall,,  or  sttbstance  which  might  be  movedr 
er  injured  by  their  expansion. 

115.  Expansion  of  Liqnfds, — Liquids  expand   through 
the  agency  of  heat  more  traequally,,  and  to-  a  much  greater 
extent  than  solids. 

A  column  of  water  contained  m  a  cylindrical  glass  vessel  wfll  expand 
I-23d  in  length  on  being  heated  from  the  freezing  to  the  boiling-  point,  while 
a  column  of  ironr  with  the  same  increase  of  temperaturer  will  expand  onlj- 
I-812th. 

A  familiar  illustration  of  the  expansion-  of  water  by  heat  is.  seen  in  the  over- 
flow  of  foil  vessels-  before  boiling  commences. 

Different  liquids  expand  very  unequally  with  an  equal  increase  in  tem- 
perature. 

This  may  be  illustrated  by  partially  filling-  several  glass  tubes-  furnished 
with  bulbs,  with  different  liquidSy  as  etherr  alcoholy  waterr  and  sulphuric  acid, 
-.  and  placing  them  ha  a  vessel  of  hot  water.     Their 

different  rates  of  expansion  will  cause  them  to  rise 
to  different  heights  in  the  tubes.  (See  Fig.  29.) 
•  Spirits  of  winer  on  being  heated  from  32°  to 
212°,  increase  in  bulk  one  ninth  ~  the  ©ils  expand 
one  twelfth,  and  water  gains  one  twenty- third.  A 
person  buying  oil,  molasses,  and  spirits  in  winter 
will  obtain  a  greater  weight  of  the  same  material,, 
in  the  same  measure,  than  in  summer.  Spirits,  in. 
the  height  of  summer,,  will  measure  five  per  cent, 
more  than  in  the  depth  of  winter,,  or  twenty  gal- 
lons bought  in  January  willr  under-  ordinary  circumstances,  become-  twenty- 
one  in  July. 

116.  Unequal  Expansion  of  Water,— Water,   as  It   de- 
creases in  temperature  toward  the  freezing  point.,  exhibits 
phenomena  which  are  wholly  at  variance  with  the  general 
law  that  bodies  expand  hy  heat  and  contract  hy  cold,  or 
by  a  withdrawal  of  heat. 

As  the  temperature  of  water  is  lowered,,  it  continues  to  contract  until  it 
arrives  at  a  temperature  of  39°^  P.r  when  all  further  contraction  ceases.  The 
volume  or  bulk  is  observed  to  remain  stationary  for  a  time,,  but  on  lowering; 

QUESTIONS.— What  is  said  of  the  expansion  of  liquids  2  What  peculiarities  of  expansion 
does  water  exhibit? 


THE    EFFECTS    OF    HEAT.  81 

the  temperature  still  more,  instead  of  contraction,  expansion  is  produced,  and 
this  expansion  continues  at  an  increasing  rate  until  the  water  ia  congealed. 

Water  attains  its  greatest  density,  or  the  greatest 
quantity  is  contained  in  a  given  bulk,  at  a  temperature  of 
39°  F. 

As  the  temperature  of  water  continues  to  decrease  below  396,  the  point  of 
its  greatest  density,  its  particles,  from  their  expansion,  necessarily  occupy  a 
larger  space  than  those  which  possess  a  temperature  somewhat  more  elevated* 
The  coldest  Water,  therefore,  being1  lighter,  rises  and  floats  upon  the  surface 
of  the  Warmer  Water.  On  the  approach  of  winter  this  phenomenon  actually" 
takes  place  in  our  lakes,  ponds,  and  rivers.  When  the  surface  water  become^ 
Sufficiently  chilled  to  assume  the  form  of  ice,  it  becomes  still  lighter,  and  con- 
tinues to  float.  By  this  arrangement,  watef  and  iee  being  almost  perfect 
non-conductors  of  heat,  the  great  mass  of  the  water  is  protected  from  the 
influence  of  cold,  and  prevented  from  becoming  chilled  throughout. 

A  few  other  liquids  beside  water"  expand  with  a  reduction  of  temperaturei 
Fused  iron,  antimony,  zinc,  and  bismuth,  are  examples  of  such  expansion. 
Mercury  is  a  remarkable  instance  of  the  reverse,  for  when  it  freezes,  it  suffers 
a  very  great  contraction. 

The  ordinary  temperature  at  Which  water  freezes  is  32s,  Fahrenheit's  ther- 
mometer. This  rule  applies  only  to  fresh  water  |  salt  water  never  freeze^ 
Until  the  surface  is  cooled  down  to  27°,  or  five  degrees  lower  than  the  freezing 
point  of  fresh  water. 

117.  Expansion  of  Gases,—  G-ases  are  more  expansible 
by  heat  than  either  solids,  or  liquids.  All  gases  and  all 
vapors^  except  at  the  point  of  condensation,  are  expanded 
equally  by  the  application  of  equal  additions  of  heat.  The 
rate  of  expansion  is  equal  to  the  l-490th  of  the  bulk  -which 
a  gas  possesses  at  32°  F.  for  every  degree  of  heat  which  it 
receives  above  that  point.,  and  for  every  degree  of  heat 
withdrawn  from  them  a  contraction  to  an  equal  amount 
takes  place. 

Thus  490  cubic  inches  of  air  at  32°  F.  becomes  491  cubic  inches  at  33°  F.  ; 
at  34°  F,,  492  cubic  inches  j  at  356,  493,  and  BO  on—  the  addition  of  every 
degree  of  heat  increasing  its  bulk  one  cubic  inch.  In  a  like  manner',  by  the 
withdrawal  of  heat,  490  cubic  inches  of  air  would  occupy"  an  inch  less  space 
at  31°  than  at  32a  ;  two  inches  less  at  30a,  and  so  on. 

By  means  of  this  law  We  can  easily  calculate  the  amount  of  space  which  a 


.—  At  What  temperature  does  water"  possess  the  greatest  density?  What 
beneficial  results  attend  the  expansion  of  water  in  freezing?  Do  any  other  liquids  ex- 
pand in  coOling  beside  water?  At  what  temperature  does  water  freeze?  In  what  man- 
ner do  gases  expand  ?  What  law  governs  the  expansion  of  gases  ?  How  can  wa  calculate 
the  amount  of  space  a  gas  occupies  at  a  giren  temperature  ? 

4* 


82  PRINCIPLES    OF     CHEMISTRY, 

given  volume  of  gas  will  occupy,  when  heated  tip  to  any  particular  tempera- 
ture ;  or  the  contraction  which  will  take  place  in  its  volume  through  a  reduc> 
tion  of  temperature,  A  given  volume  of  air  possessing  the  temperature  of 
freezing  water,  will  occupy  double  the  space  when  heated  490  degrees ;  and 
three  times  the  space  when  heated  980  degrees. 

118.  Theory  of  Heat  Measurement, — As  the  magnitude 
of  every  body  changes  with  the  heat  to  which  it  is  exposed, 
and  as  the  same  body,  when  subjected  to  calorific  influ- 
ences under  the  same  circumstances  has  always  the  same 
magnitude,  the  expansions  and  contractions  which  are  the 
constant  effects  of  heat,  may  be  taken  as  the  measure  of 
the  cause  which  produced  them. 

The  instruments  for  measuring  heat  are  Thermometers 
and  Pyrometers.  The  former  are  used  for  measuring 
moderate  temperatures  :  the  latter  for  determining  the 
more  elevated  degrees  of  heat. 

Liquids  are  better  adapted  than  either  solids  or  gases  for  measuring  the 
effects  of  heat  by  expansion  and  contraction ;  since  in  solids  the  direct  ex- 
pansion by  heat  is  so  small  as  to  be  seen  and  recognized  with  difficulty,  and 
in  air  or  gases  it  is  too  extensive,  and  too  liable  to  be  affected  by  variations 
in  the  atmospheric  pressure.  From  both  of  these  disadvantages  liquids  are 
free. 

The  liquid  generally  used  in  the  construction  of  thermometers  is  mercury, 
or  quicksilver. 

Mercury  possesses  greater  advantages  for  this  purpose  than  any  other 
liquid.  It  is,  in  the  first  place,  eminently  distinguished  for  its  fluidity  at  all 
ordinary  temperatures ;  it  is,  in  addition,  the  only  body  in  a  liquid  state  whose 
variations  in  volume,  or  magnitude,  through  a  considerable  range  of  tempe- 
rature are  exactly  uniform  and  proportional  with  every  increase  and  diminu- 
tion of  heat.  Mercury,  moreover,  boils  at  -a  higher  temperature  than  any 
other  liquid,  except  certain  oils ;  and,  on  the  other  hand,  it  freezes  at  a  lower 
temperature  than  all  other  liquids,  except  some  of  the  most  volatile,  such  as 
ether  and  alcohol.  Thus  a  mercurial  thermometer  will  have  a  wider  range 
than  any  other  liquid  thermometer.  It  is  also  attended  with  this  convenience, 
that  the  extent  of  temperature  included  between  melting  ice  and  boiling 
water  stands  at  a  considerable  distance  from  the  limits  of  its  range,  or  its 
freezing  and  boiling  points. 

119.  The  Mercurial  Thermometer  (see  Fig,  30)  consists 


QUESTIONS.— -What  is  the  theory  of  heat  measurement  ?  What  are  the  instruments  for 
measuring  heat  called  ?  Why  are  liquids  hest  adapted  for  indicating  by  expansion  and 
contraction  the  effects  of  heat  and  cold  ?  What  liquid  is  generally  employed  ?  What  are 
the  advantages  of  mercury  for  this  purpose  ?  Describe  the  mercurial  thermometer  ? 


THE     EFFECTS     OF     HEAT. 


essentially  of  a  glass  tube  with  a  bulb  at  one  FIO.  so. 
end,  partially  filled  with  mercury.  The  mer- 
cury, introduced  through  an  opening  in  the 
end  of  the  tube,  is  afterward  boiled,  so  as  to 
expel  all  air  and  moisture,  and  fill  the  tube  with. 
its  own  vapor.  The  open  end  of  the  tube  is 
then  closed,  by  fusing  the  glass,  and  as  the 
mercury  cools  it  contracts,  and  collects  in  the 
bulb  and  lower  part  of  the  tube,  leaving  a 
vacuum  above,  through  which  it  may  again  ex- 
pand and  rise  on  the  application  of  heat.  In 
this  condition  the  thermometer  is  complete, 
with  the  exception  of  graduation, 

120.  Graduation  of  Thermometers, — As  ther- 
mometers are  constructed  of  different  dimensions  and  capaci- 
ties, it  is  necessary  to  have  some  fixed  rules  for  graduating 
them,  in  order  that  they  may  always  indicate  the  same  tem- 
perature under  the  same  circumstances,  as  the  freezing  point, 
for  example.  To  accomplish  this  -end  the  following  plan  has 
been  adopted: — The  thermometers  are  first  immersed  in 
melting  snow  or  ice.  The  mercury  will  be  observed  to  stop 
In  each  thermometer-tube  at  a  certain  height ;  these  heights 
are  then  marked  upon  the  tubes.  Now  it  has  been  ascertained 
that  at  whatever  time  and  place  the  Instruments  may  be  -af- 
terward immersed  in  melting  snow  or  ice,  the  mercury  con- 
tained in  them  will  always  fix  itself  at  the  point  thus  marked. 
This  point  is  called  the  freezing  point  of  water. 

Another  fixed  point  is  determined  by  immersing  the  instru- 
ments in  boiling  water.  It  has  been  found  that  at  whatever 
time  or  place  the  instruments  are  immersed  in  pure  water, 
when  boiling,  provided  the  barometer  stands  at  the  height  of 
thirty  inches,  the  mercury  will  always  rise  in  each  to  a  certain  height'  This, 
therefore,  forms  another  fixed  point  on  the  scale,  and  is  called  the  boiling 
point 

So  far  as  the  determination  of  the  boiling  and  freezing 
points  of  water  are  concerned,  all  the  varieties  of  the  mer- 
curial thermometer  are  constructed  alike.  •  The  interval, 
however,  between  these  two  fixed  points  is  differently  di- 
vided in  different  instruments.  ^ 

QUESTIONS.— How  are  thermometers  graduated  ?    In  what  respect  are  all  thermometers 
alike? 


84  PRINCIPLES    OF     CHEMISTRY. 

121,  Fahrenheit's  Thermametei  —  In  the  thermometer 
most  generally  used  in  the  United  States  and  England, 
and  which  is  known  as  Fahrenheit's,  the  interval  on  the 
scale  between  the  freezing  and  boiling  points,  is  divided 
into  180  equal  parts.  This  division  is  similarly  continued 
below  the  freezing  point  to  the  place  0,  called  zero^  and 
each  division  upward  from  that  is  marked  with  the  suc- 
cessive numbers  1,  2?  3,  etc.  The  freezing  point  will  now 
be  the  32d  division,  and  the  boiling  point  will  be  the 
212th  division-.  These  divisions  are  called  degrees,,  and 
the  boiling  point  will  therefore  be  212°,  and  the  freezing 
temperature,  32°. 

Thermometers  of  this  character  are  calted  Fahrenheit's,  from  a  Durtch  phi- 
losophical instrument-maker  who  first  introduced  this  method  ©f  graduation 
in  the  year  1724. 

"  The  zero  of  a  thermometrie  scale  feas  no  relation  to  the  real  zero  of  heatr 
©r  the  point  at  which  bodies  are  entirely  deprived  of  heat.  Of  this  point  we 
kmow  nothing,  and  there  is  no-  reason  to.  suppose  we  have  erer  approached  it. 
The  scale  of  temperature  may  be  compared  to  a  chains,  extended  both  upward 
and  downward  beyond  our  sight,  "We  fix  upon  a  particular  ffnl,  and  count 
upward  and  downward  from  that  link,  and  not  from  the  beginning  ©f  the 
chain," — GRAHAM. 

In  indicating  thermometrical  degrees,  the  sign  —  is  used  to  designate  those 
below  the  zero  point,  in  order  to  distinguish  them  from  degrees  of  tbe  same 
FIG.  31.  same  above  the  zero  point.  Thus,  32°  means: 

the  32d  degree  above  zero;  and  — 32°  the 
32d  below  zero, 

122.  RcairmBr  and  Centigrade 
Thermometers,— In  addition  to  Fah- 
renheit's thermometer,  two  others 
are  extensively  used,  which  are 
known  as  Keaumnr's,  and  the  Cen- 
tigrade thermometer,  or  thermome- 
ter of  Celsius. 

The  only  difference  between  these  three  kinds 
of  thermometers  is-  the  difference  in  graduating 
the- interval  between  the  freezing  and"  boiling 
points  of  water,     Eeaumurrs  is  divided!  into  eighty  degree?,,  the  Centigrade 

QUESTIONS.— Describe  the  graduation  of  Fahrenheit's  thermometer.  What  doe?  the 
zero-  point  indicate-?  How  are  degrees  below  zero  distinguished  ?  What  other  scales  ares 
used  2  Describe  the  graduation  of  Reaumur ;  of  Centigrade. 


THE     EFFECTS     OF     HEAT.  85 

into  one  hundred,  and  Fahrenheit's  into  one  hundred  and  eighty.  According 
to  Reaumur,  water  freezes  at  0°,  and  boils  at  80°  •  according  to  Centigrade, 
it  freezes  at  0°,  and  boils  at  100°";  and  according  to  Fahrenheit,  it  freezes  at 
32°,  and  boils  at  212°  j  the  last,  very  singularly,  commences  counting,  not 
at  the  freezing  point,  but  32°  below  it.* 

The  difference  between  these  instruments  can  be  easily  seen  by  referencor 
to  Fig.  31. 

In  England,  Holland,  and  the  United  States,  the  'thermometer  most  gener- 
ally used  is  Fahrenheit's.  Reaumur's  scale  is  used  in  Germany,  and  the  Cen- 
tigrade in  France,  Sweden,  and  some  other  parts  of  Europe.  The  scale  of 
the  Centigrade  is  by  far  the  simplest  and  most  rational  method  of  graduation, 
and  at  present  it  is  almost  universally  adopted  for  scientific  purposes. 

The  scale  employed  in  the  present  work  is  that  of  Fahrenheit's, 

The  thermometer  was  invented  about  the  year  1600 ;  but,  like  many  other 
Inventions,  the  merit  of  its  discovery  is  not  to  be  ascribed  to  one  person,  but 
to  be  distributed  among  many. 

The  variety  of  circumstances  under  which  thermometers  are  used,  have 
occasioned  a  considerable  variety  in  their  form.  The  following'  are  some  of 
the  most  important  of  these  modifications. 

12&  The  Self-Registering  Thermometer  Is  a  form  of 
thermometer  contrived  for  the  purpose  of  ascertaining  the 
extremes  of  variation  which  may  occur  during  a  particular 
interval  of  time,  as  in  the  night. 


40       so       za        fa        a         fo       2<r       3 

,,l    ,  Mil, -it  I  I,  i, 71,,  i,     ,  ,,,r,,,,l,..,lr,r,  t,v,-rl,rTrL,,l.ll1.Ml  .  ...T..ni 


B 


It  consists  of  two  horizontal  thermometers'  attached  to-  one  frame;,  as"  is*  rep- 
resented in  Fig.  32,  the  one,  A,  containing  mercury,  and  the  other,.  Br  spirits- 
of  wine.  On  the  surface  of  the-  mercurial  column  in  the  tube  is  placed  a 


*  The  temperatures  expressed  by  one  thermometer  scale-  may  be-  easily  reduced  to  thai 
of  another,  by  remembering  that  9°  of  Fahrenheit  are  equivalent  to  5"  of  Centigrade,  or 
4°  of  Reanmur,  In  converting-  Fahrenheit  to  Reaumur,  or  Centigrade,,  if  the  degree  be 
above  the  freezing  point,  32°  must  be  first  subtracted,  fn  order  to  reduce  the  degrees  of 
the  other  scales  to  those  of  Fahrenheit ;  but  in  the  conversion  of  Reaumur  or  Centigrade 
to  Fahrenheit;  82a  must  be  added, 

QTTESTIONB.— When  was  the  thermometer  invented"?  What  is  a  self-registering  ther- 
mometer ?  Describe  its  construction  2 


86  PRINCIPLES     OF     CHEMISTRY. 

piece  of  steel- wire,  and  on  the  surface  of  the  spirits  of  wine,  a  piece  of  black 
enamel,  or  ivory.  As  the  spirits  contract  by  exposure  to  cold,  the  enamel 
•follows  it  toward  the  bulb  •  but  when  it  expands,  the  enamel  remains  sta- 
tionary, and  suffers  the  liquid  to  pass  by  it.  "When  the  mercury  contracts, 
the  enamel  does  not  follow  it ;  but  when  the  mercury  expands,  it  is  forced 
along.  Consequently,  it  remains  at  the  highest  temperature.  The  position, 
therefore,  of  the  two  indices  will  indicate  the  lowest  and  highest  tempera- 
tures during  any  given  time.  A  simpler  form  of  thermometer  ibr  indicating 
maximum  temperature,  has  been  constructed  by  Messrs.  Negretti  and  Zam- 
bra,  of  London,  and  is  known  by  their  names.  It  is  merely  an  ordinary  ther- 
mometer, placed  horizontally,  with  a  contraction  in  the  tube  just  above  the 
bulb.  "When  the  mercury  expands  through  heat  the  expansive  force  pushes 
the  column  past  the  contraction  without  difficulty ;  but  when  the  temperature 
falls,  and  the  expansive  force  ceases  to  act,  the  contraction  in  the  tube  pre- 
vents the  column  from  receding.  The  position  of  the  mercury  above  the 
contraction  indicates,  therefore,  the  highest  temperature  attained  since  the 
last  observation.  The  mercurial  column  is  restored  to  its  true  place,  by  a 
slight  percussion  of  the  instrument 

124.  The  Differential  Thermometer  is  a  form  of  ther- 
mometer so  named  because  it  denotes  only  differences  of 
temperature  between  two  substances,  or  two  contiguous 
portions  of  the  same  atmosphere. 

.p.  It  consists  of  two  glass  bulbs  on  one  tube,  bent  twice  at 

right  angles,  and  supported  as  represented  in  Fig.  33.  Tho 
bulbs  contain  air,  but  the  tube  is  nearly  filled  with  sulphuric 
acid  colored  red.  To  one  leg  of  the  tube  is  applied  a  scale. 
When  the  bulbs  of  this  instrument  are  heated  or  cooled  alike, 
no  change  will  take  place  in  the  columns  of  liquid,  because 
the  air  in  both  bulbs  will  undergo  an  equal  expansion  or  con- 
traction ;  but  the  instant  any  inequality  of  temperature  exists 
between  them,  as  from  bringing  a  heated  substance  near  to 
one  of  them,  the  liquid  in  the  two  legs  will  rise  and  fall  rapidly. 

125.  Metallic  Thermometer, — A  very  delicate 
thermometer,  known  as  the  metallic,  or  Bre- 
guet's  thermometer,  is  constructed  on  the  principle  of  the 
unequal  expansion  of  two  metals. 

It  consists  (see  Fig.  34)  of  two  equal  strips  of  platinum  and  silver,  firmly 
soldered  together  and  coiled  in  the  form  of  a  spiral.  One  end  of  the  spiral 
is  suspended  from  a  fixed  point,  while  the  lower  end  is  free  and  carries  an 
index.  Variations  of  temperature  cause  the  two  metals  to  expand  and  con- 


QTTEBTIONB.— What  is  the  thermometer  of  NegrettS  and  Zambra  ?  What  is  a  differential 
thermometer  ?  Describe  its  construction.  Describe  the  metallic,  or  Breguet's  thermom- 
eter. 


THE     EFFECTS     OF     HEAT. 


87 


tract  unequally,  and  the  spiral  to  twist  FIG.  34 

in  opposite  directions.  These  mo- 
tions imparted  to  the  index,  cause  it 
to'  move  over  a  graduated  circle,  on 
which  degrees  are  indicated.  So  sen- 
sitive is  this  instrument,  that  when 
inclosed  in  a  large  receiver,  which  was 
rapidly  exhausted  by  an  air  pump,  it 
indicated  a  reduction  of  temperature 
From  G'3°  to  25°-=-"41°,  while  a  mer- 
curial thermometer  fell  only  to  36°. 

For  chemical  purposes,  thermom- 
eters are  sometimes  constructed  in 
such  a  way,  that  the  lower  part  of  the 
scale  turns  up  by  a  hinge,  in  order  to 
allow  the  bulb  to  be  immersed  in  cor- 
rosive liquids.  (See  Fig.  35.) 

126.  Air    Thermometers, — 
The  first  thermometer  used  consisted  of  a  column  of  air  confined  in  a  glass 
FIG.  35.  tube  over  colored  water.     Heat  ex-  pIG  ^ 

pands  the  air  and  increases  the  length 
of  the  column  downward,  pushing  the 
water  before  it :  cold  produces  a  con- 
trary effect.  The  temperature  is  thus 
indicated  by  the  height  at  which  the 
water  is  elevated  in  the  tube.  Fig.  36 
represents  the  principle  of  the  con- 
struction of  the  air  thermometer. 

Fig.  37  represents  an  air  thermom- 
eter filled  up  with  a  scale,  and  termed 
the  thermometer  of  Sanctorius,  from  its  inventor.  FIG.  37. 

127.  Spirit  Thermometers . — As  the  temperature  ^^ 
is  lowered,  the  mercury  in  Fahrenheit's  thermometer  gradually  finks, 
until  it  reaches  a  point  39°  below  zero,  where  it  freezes.  Mercury, 
therefore,  can  not  be  made  available  for  measuring  cold  of  a  greater 
intensity.  This  difficulty  is,  however,  obviated  by  using  a  thermom- 
eter filled  with  alcohol  colored  red,  as  this  fluid,  when  pure,  never 
Freezes,  but  will  continue  to  sink  lower  and  lower  in  the  tube  as  the 
cold  increases.  Such  a  thermometer  is  called  a  spirit  thermometer. 

128.  P  y  r  o  m  e  t  e  r  s  .—If  a  Fahrenheit's  thermometer  be  heated, 
the  mercury  contained  in  it  will  rise  in  the  tube  until  it-  reaches  660°, 
at  which  temperature  it  begins  to  boil.  A  slight  additional  heat 
forms  vapor  sufficient  to  burst  the  tube.  Mercury,  therefore,  can  not  be  used 

QUKSTIONS. — What  was  the  first  thermometer  used  ?  How  is  cold  of  great  intensity  in- 
dicated ?  How  is  heat  of  great  intensity  measured  ?  Describe  the  principle  upon  which 
the  pyrometer  is  constructed. 


88 


PRINCIPLES     Of1     CHEMISTRY, 


to  measure  degrees  of  heat  of  greater  intensity  than  660°  F,  Temperatures 
greater  than  this  are  determined  by  means  of  the  expansion  of  solids  ;  and 
instruments  founded  upon  this  principle  are  commonly  called  pyrometers. 

FIG.  38. 


The  principle  of  the  construction  of  the  pyrometer  is  shown  in  Fig,  38, 
A  represents  a  metallic  bar,  fixed  at  one  end,  B,  but  left  free  at  the  other, 
and  in  contact  with  the  end  of  a  pointer,  K,  moving'  freely  over  a  graduated 
scale.  If  the  bar  be  heated  by  the  flame  of  alcohol,  the  metal  expands,  and 
pressing  upon  the  end  of  the  pointer,  moves  it,  in  a  greater  or  less  degree, 
In  this  manner,  the  effect  of  heat,  applied  for  a  given  length  of  time,  to  bars 
of  different  metals,  having  the  same  length  and  diameter,  may  be  determined, 

The  pyrometer  of  practical  use  is  known  as  Daniel's,  and  consists  of  a1 
platinum  bar  inclosed  in  a  tube  of  black-lead,  closed  at  the  bottom,  The 
whole  is  then  placed  in  the  fire,  or  in  a  mass  of  melted  metal,  whose  tem- 
perature it  is  desirable  to  ascertain.  The  platinum  expands  much  more  than 
the  case  which  incloses1  it,  and  projecting  upward,  moves  a  lever,  which  drives 
forward  an  index  over  a  graduated  arc. 

A  thermometer  does  not  inform  us  how  much  heat  any  substance  contains, 
but  it  merely  points  out  the  difference  in  the  temperature  of  two  or  more 
Bubstances.  All  we  learn  by  the  thermometer  is  whether  the  temperature 
of  one  body  is  greater  or  less  than  that  of  another ;  and  if  there  is  a  differ- 
ence, it  is  expressed  numerically — namely,  by  the  degrees  of  the  thermonv 
eter.  It  must  be  remembered  that  these  degrees  are  part  of  an  arbitrary 
scale,  selected  for  convenience,  without  any  reference-  whatever  to  the  actual 
quantity  of  heat  present  in  bodies. 

129.  Fluidity  as  an  Effect  of  Heat.— The  first  ef&ct 
produced  by  teat  upon  solid s  is  expansion.  If  the  heat 
l)e  augmented,  they  change  their  aggregate  state,  and 
melt,  or  become  liquid.  Many  solids  become  soft  before 
melting,  so  that  they  may  be  kneaded  ;  for  instance,  wax, 

QTTESTIONS.— Describe  Daniel's  pyrometer.  Does  the  thermometer  inform  us  how  much 
heat  a  body  contains  ?  After  the  expansion  of  bodies  by  heat,  what  other  effect*  a™  next 
observed  ? 


THE     EFFECTS     OF     II  EAT.  89 

glass,  and  iron.     In  this  position,  glass  can  be  bent  and 
molded  with  facility,  and  iron  can  be  forged  or  welded. 

130.  Liquefaction, — By  liquefaction  we  understand  the 
conversion  of  a  solid  into  a  liquid  by  the  agency  of  heat, 
as  solid  ice  is  converted  into  water  by  the  heat  of  the  sun. 

The  temperature  at  which  liquefaction  takes  place  is  called 
the  melting  point,  or  point  of  fusion  ;  and  that  at  which 
liquids  solidify,  the  freezing  point,  or  point  of  congelation. 

The  melting  point  of  a  given  solid  is  always  fixed  and 
constant,  but  the  degree  of  heat  at  which  different  solids 
melt  varies  exceedingly. 

Thus,  platinum  is  not  melted  at  3280°  •  iron  melts  at  about  2800° ;  lead 
at  612°;  wax,  142°;  tallow,  92° ;  olive  oil,  36°;  ice,  32°;  milk,  30°;  oil 
of  turpentine,  14°  j  mercury,  —  39° ;  liquid  ammonia,  —  46°  ;  while  pure 
alcohol,  having  never  been  solidified,  possesses  no  known  melting  point. 

131.  Vaporization, — By  vaporization  is  meant  the  con- 
version of  liquid  and  solid  substances  into  vapor,  through 
the  agency  of  heat.     Thus  water,  if  heated  sufficiently, 
will  be  converted  into  steam.     It  is  generally  supposed 
that  all  solid  and  liquid  substances,  under  the  influence  of 
a  sufficient  degree  of  heat,  are  susceptible  of  this  change. 

A  gas  differs  from  a  vapor  in  the  circumstance  that  it 
is  not  so  easily  condensed  into  a  liquid,  but  permanently 
retains  its  state  under  all  ordinary  conditions  of  tempera- 
ture and  pressure. 

132.  Condensation, — If  a  body  in  a  state  of  vapor  lose 
heat  in  sufficient  quantity,  it  will  pass  into  a  liquid  or 
solid  state.     Thus,  if  a  certain  quantity  of  heat  be  ab- 
stracted from  steam,  it  will  become  water.     I^iis  change 
is  called  CONDENSATION. 

The  change  from  a  state  of  vapor  to  a  liquid  is  termed  condensation,,  be- 
cause, in  so  doing,  the  body  always  undergoes  a  very  considerable  diminution 
of  volume,  and  therefore  becomes  condensed. 

133.  Volatile   and   Fixed   Bodies , — Substances  according  to  the 
facility  with  which  they  yield  vapor,  are  said  to  be  volatile,  or  fixed  and  nou- 

QTTESTIONB.— What  is  liquefaction?  What  is  said  respecting  the  melting  point  of 
todies?  What  is  vaporization  ?  How  does  a  gas  differ  from  a  vapor  ?  What  is  meant 
by  the  term  condensation  as  applied  to  vapors  ?  What  is  sublimation  ?  What  is  the  dis- 
tinction between  fixed  and  volatile  substances  ? 


90  PRINCIPLES     OF     CHEMISTRY. 

volatila  A  volatile  substance  is  one  which  yields  vapor  readily  by  the  ap- 
plication of  heat,  and  wastes  away  on  simple  exposure  to  the  atmosphere. 
Those  substances,  on  the  contrary,  are  said  to  be  fixed  and  non-volatile, 
which  have  little  or  no  tendency  to  assume  the  condition  of  vapor.  Thus, 
iron  is  a  fixed  substance,  because  it  does  not  suffer  a  sensible  degree  of 
waste  when  exposed  to  intense  heat  Oils  which  do  not  evaporate  on  simple 
exposure  to  the  atmosphere  are  also  termed  fixed,  to  distinguish  them  from 
those  which  yield  vapor  under  the  same  circumstances. 

The  melting  of  a  solid,  or  its  conversion  into  a  liquid,  only  occurs  when  the 
solid  is  heated  up  to  a  certain  fixed  point ;  but  the  conversion  of  a  liquid 
into  a  vapor  takes  place  at  all  temperatures.  . 

Thus,  the  vapor  of  water  is  continually  passing  off  from  the  surface  of  the 
soil,  from  the  ocean,  and  from  all  animal  and  vegetable  productions.  The 
production  of  vapor  also  takes  place  to  a  very  considerable  extent  from  the 
surface  of  snow  and  ice,  even  when  the  temperature  of  the  air  is  far  below 
the  freezing  point 

This  circumstance  explains  the  waste  of  snow  and  ice  which  may  be  ob- 
served during  the  continuance  of  severe  cold- 

134.  Vapors  Invisible, — The  vapor  of  water,   and  all 
other  vapors,  are  invisible  and  transparent.     The  water 
which  has  hecome  diffused  through  the  air  by  evaporation 
only  becomes  visible  when,  on  returning  to  its  fluid  con- 
dition, it  forms  mist,  cloud,  dew,  rain,  etc. 

Steam,  which  is  the  vapor  of  boiling  water,  is  invisible,  but  when  it  comes 
in  contact  with  air,  which  is  cooler,  it  becomes  condensed  into  small  drops, 
and  is  thus  rendered  visible. 

The  proof  of  this  may  be  found  in  examining  the  steam  as  it  issues  from 
an  orifice,  or  the  spout  of  a  boiling  kettle :  for  a  short  space  next  to  the  open- 
ing no  steam  can  be  seen,  since  the  air  is  not  able  to  condense  it ;  but  as  it 
spreads  and  comes  in  contact  with  a  larger  volume  of  air,  the  invisible  vapor 
becomes  condensed  into  drops,  and  is  thus  rendered  visible. 

The  visible  matter  popularly  called  steam,  should  be,  therefore,  distin- 
guished from  steam  proper,  or  the  aeriform  state  of  water.  The  cloud,  or 
smoke-like  matter  observed,  is  really  not  an  air  or  vapor  at  all,  but  a  collec- 
tion of  minute^bubbles  of  water,  wafted  by  a  current  either  of  true  steam,  or, 
more  frequently,  of  mere  moist  air. 

The  surface  of  any  watery  liquid,  whose  temperature  is  about  20°  warmer 
than  any  superincumbent  air,  rapidly  gives  off  true  steam.  It  is  not  neces- 
sary, therefore,  for  the  production  of  steam,  that  water  should  be  raised  to 
the  boiling  temperature. 

135.  Comparative  Volume  of  Vapors, — Liquids  in  pass- 

QITESTIONS. — Do  vapors  form  at  all  temperatures  ?  Are  vapors  really  visible  ?  Is  steam 
invisible  ?  What  is  the  proof  of  it  ?  At  what  temperature  is  steam  produced  ?  What  is 
the  comparative  volume  of  vapors  ? 


THE     EFFECTS    OF    HEAT.  91 

ing  into  vapors  occupy  a  much  greater  spac3  than  the  sub- 
stances from  which  they  are  produced.  Water,  in  passing 
from  .its  point  of  greatest  density  into  steam,  expands  to 
nearly  1700  times  its  volume. 

136.  Density  of  Vapors,— Vapors  are  of  all  degrees  of 
density.     The  vapor  of  water  may  be  as  thin  as  air,  or  al- 
most as  dense  as  water. 

The  subject  of  vaporization  may  be  considered  under  two  heads,  viz., 
evaporation  and  ebullition. 

137.  Evaporation,— When  vaporization  takes  place  only 
from  the  surface  of  a  body,  either  because  the  heat  has 
access  to  that  part,   or  because  the  evolution  of  vapor 
takes  place  through  the  medium  of  a  gas  or  air  present, 
the  action  can  only  be  recognized  by  the  diminution  of  the 
bulk  of  the  body  ;  this  phenomenon  is  termed  Evapora- 
tion. 

138.  Ebullition, — When  a  liquid  is  heated  sufficiently 
to  form  steam,  the  production  of  vapor  takes  place  prin- 
cipally at  that  part  where  the  heat  enters  ;  and  when  the 
heating  takes  place  not  from  above,  but  from  the  bottom 
and  sides,  the  steam  as  it  is  produced  rises  in  bubbles 
through  the  liquid,  and  produces  the  phenomenon  of  boil- 
ing, or  ebullition. 

Boiling,  therefore,  may  be  denned  to  be  the  mechanical  agitation  of  a  fluid 
by  its  own  vapor. 

139.  Boiling  Point. —The  temperature  at  which  vapor 
rises  with  sufficient  freedom  to  cause  the  phenomenon  of 
ebullition,  is  called  the  boiling  point. 

140.  Conditions  of  Evaporation,  —  Evaporation    takes 
place  from,  the  surfaces  of  bodies  only,  and  is  influenced 
in  a  great  degree  by  the  temperature,  dryness,  stillness, 
and  density  of  the  atmosphere/* 

*  It  is  a  common  error  that  the  Bun's  rays  are  the  first  source  of  evaporation,  and  many 
persons  ignorantly  imagine,  that  because  a  locality  is  sunny  it  is  sure  to  be  dry.  It  can, 
however,  be  shown,  by  a  great  variety  of  facts,  that  the  wind  has  more  to  do  with  drying 

QUESTIONS.— What  is  said  of  the  .density  of  vapors  ?  In  what  two  ways  may  liquids  be 
vaporized  ?  What  is  evaporation  ?  What  is  ebullition  ?  Define  boiling  and  the  boiling 
point.  What  are  the  conditions  of  evaporation  ? 


92  PRINCIPLES     OF     CHEMISTRY. 

"When  water  is  covered  by  a  stratum  of  dry  air,  the  evaporation  is  rapid, 
even  when  its  temperature  is  low ;  whereas  it  goes  on  very  slowly  if  the  at- 
mosphere contains  much  vapor,  even  though  the  air  be  very  warm. 

Evaporation  is  far  slower  in  still  air  than  in  a  current.  The  air  imme- 
diately in  contact  with  the  water  soon  becomes  moist,  and  thus  a  check  is 
put  to  evaporation.  But  if  the  air  be  removed  by  wind  from  the  surface  of 
the  water  as  soon  as  it  has  become  charged  with  vapor,  and  its  place  sup- 
plied with  fresh  air,  therj  the  evaporation  continues  on  without  interruption. 

Air  without  vapor  (theoretically  known  as  dry  air)  does  not  exist  hi  na- 
ture, and  can  not  probably  be  produced  by  art. 

141.  Capacity  for  Absorption,— Air  absorbs  moisture  at 
all  temperatures,  and  retains  it  in  an  invisible  state.  This 
power  of  the  air  is  termed  its  capacity  for  absorption. 

The  capacity  of  air  for  moisture  increases  with  the  tem- 
perature. 

and  evaporation  than  the  sun.  In  the  formation  of  ice  on  ponds,  for  instance,  on  a  windy 
night  in  extreme  winter,  nothing  is  actually  gained,  since  the  ice  wastes  by  evaporation 
from  the  surface  as  fast  as  it  forms  beneath.  Every  housewife  knows  that  wet  linen 
dries  more  rapidly  when  flying  in  the  cold  wind,  than  when  hanging  quietly  in  the  warm 
sun.  The  driving  blast  which  accompanies  those  sudden  showers  that  vex  and  drench 
travelers  in  mountain  regions,  brings  an  almost  instant  remedy  when  the  shower  has 
passed.  Air  at  rest  will  take  up  only  a  limited  quantity  of  moisture,  and  is  speedily  satu- 
rated. But  air  in  motion  is  never  satisfied,  and  is  constantly  abstracting  moisture  from 
the  soil.  It  is  not  the  character  of  the  soil,  but  the  constant  aud  unobstructed  motion  of 
the  air,  which  reduces  open  land  to  barrenness. 

"  A  proper  understanding  of  the  influence  which  trees  and  forests  have  upon  the  fer- 
tility of  a  country,  by  controling  the  evaporation  of  moisture  from  its  surface,  is  of  great 
practical  importance.  It  is  matter  of  surprise  to  every  one  who  journeys  in  Syria  or 
Greece,  that  the  sacred  and  classic  streams  should  be  of  such  mean  dimensions.  The 
circumstance,  however,  finds  an  explanation  in  the  fact,  that  the  hills  of  these  countries 
have  been  almost  entirely  deprived  of  their  forests.  And  the  like  cause  will  everywhere 
produce  the  like  effect.  In  an  open  country,  the  absolute  quantity  of  water  which  the 
rivers  discharge  is  not  only  less  than  in  a  wooded  country,  but  the  flow  is  incomparably 
more  irregular  and  unequal.  It  has  been  especially  noticed  in  the  Western  States,  that 
since  the  country  has  been  extensively  cleared,  the  alternations  of  the  '  stage5  of  water 
in  the  rivers  have  been  more  marked  and  violent.  In  New  England  the  effect  of  an  indis- 
criminate clearing  away  of  forests  has  been  practically  illustrated  by  the  constant  hin- 
derance  of  mill-streams  from  drought  and  freshets.  Many  water-privileges  which,  half  a 
century  ago,  were  valuable  and  steady,  have  now  become  nearly  worthless.  The  dam 
which  was~conveniently  put  up  to  saw  an  adjoining  forest  into  profitable  plank,  now 
that  its  excellent  work  is  done,  will  drive  the  saw  in  the  summer  no  longer.  Many  of  the 
larger  New  England  factories  have  been  compelled  to  introduce  steam-power  to  supply  a 
deficiency  in  the  volume  of  water,  which  st  few  years  ago  was  not  troublesome.  The  cut- 
ting away  of  forests  does  not  probably  diminish  the  quantity  of  rain  or  snow,  although 
some  authorities  maintain  that  this  is  the  fact ;  but  it  deprives  the  moisture  of  its  bene- 
ficent effect  upon  the  earth,  by  causing  it  to  be  too  rapidly  abstracted — thus  producing 
pernicious  alternations  of  freshet  and  drought,  which  are  as  fatal  to  the  health  of  the  soil, 
as  to  the  health  of  the'men  who  own  the  soil." 

<JxiE8TioN8. — Does  air  exist  without  vapor  ?  What  is  understood  by  the  capacity  of  ab- 
sorption in  air  ? 


THE    EFFECTS    OF    HEAT.  93 

A  volume  of  air  at  32°  can  absorb  an  amount  of  moisture  equal  to  the  hun- 
dred and  sixtieth  part  of  its  own  weight,  and  for  every  27  additional  degrees 
of  heat,  the  quantity  of  water  it  can  absorb  at  32°  is  doubled.  Thus  a  body 
of  air  at  32°  F.  absorbs  the  160th  part  of  its  own  weight ;  at  59°  F.,  the  80th; 
at  86°  F.,  the  40th  ;  at  113°  F.,  the  20th  part  of  its  own  weight  in  moisture. 
It  follows  from  this  that  while  the  temperature  of  the  air  advances  in  an 
arithmetical  series,  its  capacity  for  moisture  is  accelerated  in  a  geometrical 
series. 

Air  is  said  to  be  saturated  with  moisture  when  it  con- 
tains as  much  of  the  vapor  of  water  as  it  is  capable  of 
holding  with  a  given  temperature. 

142.  Hy-grom'e-ters, — Instruments  designed  for  meas- 
uring the  quantity  of  moisture  contained  in  the  atmos- 
phere, are  called  HYGROMETERS.* 

Many  organic  bodies  have  the  property  of  absorbing  vapor,  and  thus  in- 
creasing their  dimensions.  Among  such  may  be  mentioned  hair,  wood,  whale- 
bone, ivory,  etc.  Any  of  these  connected  with  a  mechanical  arrangement  by 
Which  the  change  in  volume  might  be  registered,  would  furnish  a  hygrome- 
ter. The  thin,  transparent  shavings  of  whalebone,  which  by  bending  and 
rolling  up  when  placed  upon  the  warm  hand,  constitute  the 
so-called  sensitive  figures,  are  illustrations  of  this  prin- 
ciple. 

If  we  fix  against  a  wall  a  long  piece  of  catgut,  and  hang 
a  weight  to  the  end  of  it,  it  will  be  observed,  as  the  air 
becomes  moist  or  dry,  to  alter  in  length ;  and  by  marking 
a  scale  the  two  extremities  of  which  are  determined  by  ob- 
servation when  the  air  is  very  dry,  and  when  it  is  saturated  || 
with  moisture,  it  will  be  found  easy  to  measure  the  varia-  '' 
tions. 

143.  Hair   Hygrometer , — An  instrument  called 
the  "  Hair  Hygrometer,"  is  constructed  upon  this  principle. 
It  consists  of  a  human  hair,  fastened  at  one  extremity  to  a 
screw  (see  Fig.  39),  and  at  the  other  passing  over  a  pulley, 
being  strained  tight  by  a  silk  thread  and  weight,  also  at- 
tached to  the  pulley.     To  the  axis  of  the  pulley  an  index 
is  attached,  which  passes  over  a  graduated  scale,  so  that  as 
the  pulley  turns,  through  the  shortening  or  lengthening  of 
the  hair,  the  index  moves.     When  the  instrument  is  in  a 
damp  atmosphere,  the  air  absorbs  a  considerable  amount 
of  vapor,  and  is  thus  made  longer,  while  in  dry  ah"  it  be- 

*  Hygrometer,  from  the  Greek  words  v-ypog  (moist)  and  pcrpov  (measure). 

QUESTIONS. — When  Is  air  said  to  be  saturated  with  moisture  ?  What  are  hygrometers  ? 
Explain  the  hair  hygrometer  and  its  principle  of  construction  ? 


94 


PRINCIPLES    OF    CHEMISTRY. 


comes  shorter ;  so  that  the  index  is  of  course  turned  alternately  from  one  Bide 
to  the  other. 

The  instrument  is  graduated  by  first  placing  it  in  air  artificially  made  as 
dry  as  possible,  and  the  point  on  the  scale  at  which  the  index  stops  under 
these  circumstances,  is  the  point  of  greatest  dryness,  and  is  marked  0.  The 
hygrometer  is  then  placed  in  a  confined  space  of  air,  which  is  completely 
saturated  with  vapor,  and  under  these  circumstances  the  index  moves  to  the 
other  end  of  the  scale :  this  point,  which  is  that  of  greatest  moisture,  ia 
marked  100.  The  intervening  space  is  then  divided  into  100  equal  parts, 
which  indicate  different  degrees  of  moisture. 


FIG.  40. 


144  Daniel's  Hygrometer,  —  Another 
form  of  hygrometer,  known  as  "Daniel's  Hygrom- 
eter," determines  the  moisture  in  the  air  by  indicat- 
ing the  dew  point,  or  the  temperature  at  which 
moisture  is  deposited  from  the  ah*.  It  consists  of  a 
bent  tube  of  glass,  Fig.  40,  at  the  extremities  of 
which  two  bulbs,  a  and  b,  are  blown.  The  bulb  6 
is  made  of  black  glass,  and  contains  a  little  ether, 
into  which  dips  the  ball  of  a  small  and  delicate 
thermometer,  contained  in  the  cavity  of  the  tube. 
The  whole  instrument  -contains  only  the  vapor  of 
ether,  the  air  having  been  removed.  The  bulb  a  is 
covered  over  with  a  piece  of  muslin.  The  support 
of  the  tube  sustains  another  thermometer,  by  which 
we  can  observe  the  temperature  of  the  air.  When 
an  observation  is  to  be  made  with  this  instrument, 
a  little  ether  is  poured  on  the  muslin  of  the  bulb  a;  this  evaporates  rapidly, 
and  by  so  doing  reduces  the  temperature  of  the  other  bulb,  6.  As  soon  as 
this  has  cooled  sufficiently  to  condense  the  moisture  of  the  atmosphere,  dew 
will  be  observed  to  collect  upon  it,  and  the  temperature  at  which  the  deposi- 
tion takes  place  is  determined  by  observing  the  thermometer  included  in  the 
tube.  If  the  air  is  very  moist,  it  is  necessary  to  cool  the  bulb  6  but  very  little 
before  dew  is  deposited  upon  it ;  if,  however,  the  air  is  very  dry,  the  cooling 
must  be  carried  to  a  corresponding  lower  degree.  If  the  air  is  perfectly 
saturated,  the  slightest  depression  of  temperature  will  cause  its  moisture  to 
precipitate.  Knowing,  therefore,  the  temperature  of  the  dew  point,  we  are 
enabled  by  tables  calculated  for  the  purpose,  to  determine  the  proportional 
amount  of  moisture  contained  in  the  atmosphere. 

145.  Conditions  of  Ebullition,— Different  liquids  boil 
at  different  temperatures,  but  the  boiling  point  of  the 
same  liquid  is  always  the  same  under  the  same  circum- 
stances. The  boiling  temperature,  therefore,  constitutes 
a  distinctive  characteristic  of  a  liquid,  and  in  practical 


QUESTIONS.— Describe  Daniel's  hygrometer.     How  does  the  boiling  point  of  liquids  vary  ? 


THE     EFFECTS      OF    HEAT.  95 

chemistry  often  affords  a  ready  method  of  detecting  a  dif- 
ference in  the  chemical  composition  of  similar  liquids. 

Thus  water,  under  ordinary  circumstances,  begins  to 
boil  when  it  is  heated  up  to  212°  F. ;  alcohol  at  173°  ; 
ether  at  96° ;  syrup  at  221°  ;  linseed  oil  at  640°. 

146.  Salinometer  , — Water  containing  any  dissolved  matter  boils  at  a 
higher  temperature  than  when  pure — the  boiling  point  on  the  thermometric 
scale  rising  in  proportion  as  the  amount  of  matter  dissolved  in  tho  water  in- 
creases.    Advantage  is  taken  of  this  principle  in  the  construction  of  an  instru- 
ment known  as  the  "Salinometer,"  which  is  especially  used  by  salt-boilers 
for  indicating  the  quantity  of  salt  held  in  solution  in  the  water  of  the  boilers. 
It  simply  consists  of  a  delicate  thermometer  arranged  in  connection  with  the 
interior  of  the   boiler,   and  by  means  of  a  properly  graduated  scale,  the 
percentage  of  salt  held  in  the  water  is  indicated  by  the  boiling  point  of  the 
water. 

147.  Influence  of  Atmospheric  Pressure  onBoilin g, — 
Liquids,  in  general,  being  boiled  in  open  vessels,  are  subjected  to  the  pressure 
of  the  atmosphere.     The  tendency  of  this  pressure  is  to  prevent  and  retard 
the  particles  of  water  from  expanding  to  a  sufficient  extent  to  form  steam. 
Hence,  if  the  pressure  of  the  atmosphere  varies,  as  it  does  at  different  times 
and  places,  or  if  it  be  increased  or  diminished  by  artificial  means,  the  boiling 
point  of  a  liquid  will  undergo  a  corresponding  change. 

The  pressure  of  the  atmosphere  at  the  level  of  the  sea  is  about  fifteen 
pounds  upon  each  square  inch  of  surface.  It  varies  occasionally  at  the  same 
place  sufficiently  to  affect  the  boiling  point  to  the  extent  of  4£  degrees. 

148.  Measurement    of    Altitudes  — As  we  ascend  into  the  at- 
mosphere tho  pressure  is  diminished,  because  there  is  less  of  it  above  us ; 
it  therefore  follows,  that  water  at  different  heights  in  the  atmosphere  will  boil 
at  different  temperatures,  and  it  has  been  found  by  observation,  that  an  ele- 
vation of  550  feet  above  the  level  of  the  sea  causes  a  difference  of  one  de- 
gree in  its  boiling  point.     Hence  the  boiling  point  of  water  becomes  an  in- 
dication o'f  the  height  of  any  station  above  the  sea-level,  or  in  other  words, 
an  indication  of  the  atmospheric  pressure  ;  and  thus  by  means  of  a  kettle  of 
boiling  water  and  a  thermometer,  the  height  of  the  summit  of  any  mountain 
may  be  ascertained  with  a  great  degree  of  accuracy.     If  the  water  boils  at 
211°  by  the  thermometer,  the  height  of  the  place  is  550  feet ;  if  at  210°,  the 
height  is  1100  feet,  and  so  on,  it  being  only  necessary  to  multiply  550  by  the 
number  of  degrees  on  the  thermometer  between  the  actual  boiling  point  and 
212°,  to  ascertain  the  elevation.     In  the  city  of   Quito,  in  South  America, 
water  boila  at  194°  2"  F. ;  its  height  above  the  sea-level,  is,  therefore,  9,541 
feet. 

As  we  descend  into  mines,  the  pressure  of  the  atmosphere  is  increased,  there 

QUESTIONS.— What  influence  has  the  pressure  of  the  atmosphere  upon  the  boiling 
point?  How  may  the  height  of  mountains  be  determined  by  the  boiling  point  of  water  ? 


96  PRINCIPLES    OF     CHEMISTRY. 

being  more  of  it  above  us  than  at  the  surface  of  the  earth.  Water,  therefore, 
must  bo  heated  to  a  higher  temperature  before  it  will  boil,  and  it  has  been 
found  that  a  descent  of  550  feet,  as  before,  makes  a  difference  of  one  degree. 

Boiling  water  is,  consequently,  not  equally  hot  at  all  places  upon  the  earth, 
and,  therefore,  .not  every  where  alike  applicable  for  domestic  purposes.  Thus 
at  Quito  and  at  the  hospital  of  St.  Bernard,  in  Switzerland,  great  difficulty 
is  experienced  in  cooking  eggs  by  boiling. 

In  a  like  manner,  if  by  artificial  means  we  increase  or  diminish  the  pressure 
of  the  atmosphere  on  the  surface  of  a  liquid,  we  change  its  boiling  point. 
If  water  be  heated  in  a  vacuum,  ebullition  will  commence  at  a  point  140° 
lower  than  hi  the  open  air  If  a  vessel  of  ether  be  placed  under  the  receiver 
of  an  air-pump,  and  the  atmospheric  pressure  removed  from  its  surface,  the 
vapor  rises  so  abundantly  that  ebullition  is  produced  without  any  increase  of 
temperature. 

149.  Pulse-Glass . — This  principle  is  illustrated  by  a  simple  instrument 

called  the   pulse-glass,   Fig.  41,   which 
consists  of  a  glass  tube,  c,  with  bulbs,  a 
an(i  fy  blown  upon  each  extremity;  the 
c  "»  ^013  is  tneri  fii]eci  with  spirits  of  wine 

and  its  vapor,  and  hermetically  sealed. 
The  pressure  of  the  air  being  thus  removed  from  the  surface  of  the  liquid, 
the  heat  of  the  hand  upon  either  bulb  is  sufficient  to  cause  a  violent  ebul- 
lition. 

150.  Culinary    Paradox . — The  fact  that  water  boils  at  a  reduced 
temperature  under  diminished  pressure,  is  illustrated  by  an  experiment  known 
as  the  culinary  paradox.     A  glass  flask,  containing  boiling  water  is  closed 

FIG.  42  tightly  with  a  cork,  and  then  inverted,  as  in  Fig.  42.  The 
boiling  will  instantly  cease, .owing  to  the  pressure  of  the 
steam  which  is  formed,  upon  the  surface  of  the  liquid.  If 
we  now  pour  cold  water  upon  the  outside  of  the  flask,  the 
steam  within  is  condensed,  and  a  partial  vacuum  produced, 
which  causes  the  boiling  to  recommence  with  great  energy. 
On  the  other  hand,  by  pouring  hot  water  upon  the  outside 
of  the  flask,  the  steam  and  consequent  pressure  within  is  re- 
newed, and  the  boiling  ceases. 

A  proof  also  that  steam  in  escaping  from  boiling  water  is 
obliged  to  overcome  the  pressure  of  the. atmosphere,  is  ob- 
tained by  repeating  the  last  experiment  with  a  tin  canister 
instead  of  a  globular  glass  flask.  On  cqrking  up  the  canister  and  pouring 
cold  water  over  it,  the  steam  within  is  suddenly  condensed,  a  vacuum  is  pro- 
duced, and  the  canister  is  instantly  crushed  in  by  the  pressure  of  the  exter- 
nal air. 


QUESTIONS. — How  may  the  boiling  point  of  a  liquid  be  elevated  or  depressed  by  artificial 
means?  What  is  the  pulse-jrlass ?  What  is  the  culinary  paradox?  What  experiment 
proves  that  steam  in  escaping  is  obliged  to  overcome  the  pressure  of  the  atmosphere  ? 


THE    EFFECTS    OF    HEAT.  97 

151.  Sugar  Boiling , — Several  beautiful  applications  in  the  arts  havo 
been  made  of  the  principle  that  liquids  boil  at  a  lower  temperature  when 
freed  from  the  pressure  of  the  atmosphere  than  in  the  open  air. 

In  the  refining  of  sugar,  if  the  syrup  is  boiled  in  the  open  air,  the  tempera- 
ture of  the  boiling  point  is  so  high  that  portions  of  the  sugar  become  decom- 
posed by  the  excess  of  heat,  and  lost  or  injured ;  the  syrup  is  therefore  boiled 
in  close  vessels  from  which  the  air  has  been  previously  exhausted,  and  in  this 
way  the  water  of  the  syrup  may  be  evaporated  at  a  temperature  so  low  as  to 
prevent  all  injury  from  heat 

152.  Influence   of  Adhesion   on   the   Boiling   Point, — 
Adhesion  of  the  fluid  to  the  surface  of  the  vessel  that  contains  it,  has  a  marked 
effect  in  raising  the  boiling  point     Water  boils  somewhat  more  readily  in  a 
metallic  vessel  than  in  one  of  glass.     If  the  interior  of  a  vessel  be  varnished 
with  shell-lac,  the  boiling  will  not  often  occur  until  a  temperature  of  221°  F. 
is  reached,  and  then  it  will  take  place  in  bursts,  the  temperature  at  each  evo- 
lution of  vapor  falling  to  212°  F.     Boiling  can  be  made  to  take  place  steadily 
at  212°  in  any  variety  of  vessel,  by  the  Introduction  of  a  few  irregular  sub- 
stances, as  little  fragments  of  wire,  a  few  pieces  of  charcoal,  etc.     The  reason 
of  this  is  that  in  a  mass  of  boiling  liquid,  the  formation  of  vapor  takes  placo 
principally  at  the  edges  of  the  solid  substances  with  which  it  maybe  in  con- 
tact ;  and  the,  introduction  and  presence  of  irregular  surfaces  thus  facili tate 
its  formation. 

153.  Influence    of  Air    on    the    Boiling    P  o  i  n  t ,— Recent 
experiments  liave  shown  that  the  presence  of  air  In  solution  singularly  as- 
sists the  evolution  of  vapor.     Air  dissolved  in  water  acquires,  through  the 
agency  of  heat,  a  great  degree  of  elasticity,  and  minute  bubbles  of  it  are  in 
consequence  thrown  off  In  the  interior  of  a  boiling  liquid,  especially  where  it 
is  in  contact  with  a  rough  surface  ;  into  these  bubbles  the  steam  escapes  and 
rises.     "Water  when  boiled  for  a  long  time  Is  nearly  deprived  of  air ;  and  in 
such  cases  the  temperature  has  been  observed  to  rise  even  as  high  as  2  GO0, 
or  48°  above  the  boiling  point,  in  an  open  glass  vessel,  which  was  then  shat- 
tered with  a  loud  report  by  a  sudden  explosive  burst  of  vapor.     In  this  case, 
the  force  of  cohesion  retains  the  particles  of  liquid  throughout  the  mass  in 
contact  with  each  other,  in  a  species  of  unstable  equilibrium ;  and  when  this 
equilibrium  is  overturned  at  any  one  point,  the  repulsive  power  of  the  excess 
of  heat  stored  up  in  the  mass,  suddenly  exerts  itself,  and  the  explosion  is  the 
result  of  the  instantaneous  conversion  of  the  liquid  into  vapor. 

The  same  result  takes  place  when  ice,  free  from  air,  is  melted  out  of  con- 
tact with  the  atmosphere,  as  under  oil.  The  temperature  of  the  liquid  formed 
gradually  rises  to  about  260°  F.,  when,  instead  of  boiling,  it  explodes. 

If  a  single  drop  of  water  containing  air,  be  allowed  to  fall  into  a  mass  of 

QUESTIONS. — What  practical  application  of  these  principles  has  been  made  in  the  arts  ? 
What  influence  does  adhesion  have  upon  the  boiling  point  ?  How  may  liquids  be  made 
to  boil  steadily  ?  What  effect  has  air  dissolved  in  water  upon  the  evolution  of  vapor? 
What  curious  experiments  illustrate  this  ?  What  takes  place  when  ice  free  from  air  is 
heated  out  of  contact  with  air  ? 

5 


95  PRINCIPLES     OF     CHEMISTRY. 

water  freo  from  air,  which  has  been  heated  to  a  temperature  of  250°  or  260°  F., 
the  whole  volume  instantly  becomes  agitated  in  a  singular  manner,  and  an  ex- 
plosion generally  occurs. 

154.  Spheroidal  State . — When  a  drop  of  water  falls  upon  a  sur- 
face highly  heated,  as  of  metal,  it  will  be  observed  to  roll  along  the  surface 
without  adhering,  or  immediately  passing  into  vapor.  The  explanation  of 
this  is,  that  the  drop  of  water  does  not  in  reality  touch  the  heated  surface,  but 
is  buoyed  up  and  supported  on  a  layer  of  Tapor  which  intervenes  between 
the  bottom  of  the  drop  and  the  hot  surface.  This  vapor  is  produced  by  the 
heat  which  is  radiated  from  the  hot  substance,  before  the  liquid  can  come  in 
contact  with  it,  and  being  constantly  renewed,  continues  to  support  the  drop. 
The  drop  generally  rolls  because  the  current  of  air  which  is  always  passing 
over  a  heated  surface  drives  it  forward.  The  drop  evaporates  slowly,  because 
the  layer  of  vapor  between  the  hot  surface  and  the  liquid  prevents  the  rapid 
transmission  of  heat.  The  liquid  resting  upon  a  cushion  of  steam  continually 
evolved  from  its  lower  surface  by  heat,  assumes  a  rounded,  or  globular  shape, 
as  the  result  of  the  gravity  of  its  particles  toward  its  own  center. 

The  designation  which  has  been  given  to  the  condition  which  water  and 
other  liquids  assume  when  brought  in  contact  with  very  hot  surfaces,  is  that 
of  the  "  spheroidal  state." 

If  the  surface  upon  which  the  liquid  rests  is  cooled  down  to  such  an  ex- 
tent that  vapor  is  not  generated  rapidly,  and  in  sufficient  quantity  to  support 
the  drop,  it  will  come  in  contact  with  the  surface,  and  heat  being  comnmnni- 
cated  by  conduction,  will  transform  it  instantly  into  steam. 

This  is  the  explanation  of  the  practice  adopted  by  laundresses  of  touching 
a  flat-iron  with  moisture  to  ascertain  whether  the  surface  is  sufficiently  hot. 
If  the  temperature  of  the  iron  is  not  elevated  sufficiently,  the  moisture  wets 
the  surface,  and  is  evaporated  •  but  at  a  higher  degree  of  temperature,  tho 
moisture  is  repelled. 

The  phenomenon  of  the  spheroidal  condition  of  water  furnishes  an  explana- 
tion of  the  feats  often  performed  by  jugglers,  of  plunging  the  hands  with  im 
punity  into  molten  lead,  or  iron.  The  hand  is  moistened,  and  when  passed 
into  the  liquid  metal  the  moisture  is  vaporized,  and  interposes  between  tho 
metal  and  the  skin  a  sheath  of  vapor.  In  its  conversion  into  vapor,  tho 
moisture  absorbs  heat,  and  thus  still  further  protects  the  skin. 

The  bulb  of  a  thermometer  plunged  into  liquids  while  in  the  spheroidal 
state,  indicates  temperatures  considerably  below  the  ordinary  boiling  point. 
Thus  water  in  a  spheroidal  state  has  a  temperature  of  205° ;  alcohol,  167°  ; 
ether,  93° ;  sulphurous  acid,  13°.  When  distilled  water  is  allowed  to  fall 
drop  by  drop  into  sulphurous  acid  in  the  spheroidal  state,  the  water  is  in- 
stantly congealed  into  a  spongy  mass  of  ice,  even  when  the  containing  vessel 
is  red  hot. 


QTJESTIOXS. — What  takes  place  when  a  drop  of  water  falls  upon  a  highly  heated  surface  ? 
What  is  meant  by  the  spheroidal  state  ?  Why  can  the  hand  be  safely  plunged  into  molten 
iron?  What  is  the  temperature  of  liquids  in  the  spheroidal  state  ? 


THE     EFFECTS    OF   HEAT. 


99 


155.  Distillation,  or  Sublimation,  is  a  process  by  which 
one  body  is  separated  from  another  in  close  vessels,  by 
means  of  heat,  in  cases  where  one  of  the  bodies  assumes 
the  form  of  vapor  at  a  lower  temperature  than  the  other  ; 
this  first  rises  in  the  form  of  vapor,  and  is  received  and 
condensed  in  a  separate  vessel.  The  operation  is  termed 
Distillation,  when  the  vapor  formed  condenses  into  a 
liquid,  and  Sublimation  when  it  condenses  into  a  solid. 
The  product  in  the  first  instance  is  called  a  distillate,  and 
in  the  second  a  sublimate. 

When  the  product  of  one  distillation  is  subjected  to  further  distillations, 
in  order  to  free  it  to  a  still  greater  extent  from  less  volatile  substances,  the 
operation  is  called  rectification. 

By  this  means  very  volatile  bodies  can  be  easily  separated  from  less  vola- 
tile ones;  as  brandy  and 
alcohol  from  the  less  vola- 
tile water  which  may  be 
mixed  with  them.  Water 
of  extreme  purity  can  also 
be  obtained  by  distillation, 
because  the  non-volatile 
and  earthy  substances  con- 
tained in  all  spring  waters 
do  not  ascend  with  the  va- 
por, but  remain  behind  in 
the  vessel. 

Distillation  upon  a  small  scale  is  effected  by  means  of  a  peculiar-shaped  ves- 
sel, called  a  retort,  Fig.  43,  which  is  half  filled  with  a  volatile  liquid  and 


FlG.  43. 


heated;  the  steam,  as  it  forms,  passes 
through  the  neck  of  the  retort  into  a  glass 
receiver  set  into  a  vessel  filled  with  cold 
water,  and  is  then  condensed. 

When  the  operation  of  distillation  is 
conducted  on  an  extensive  scale,  a  largo 
vessel  called  a  "  stilV  is  used,  and,  for 
condensing  the  vapor,  vats  are  con- 
structed, holding  serpentine  pipes,  called 
"  worms,"  which  present  a  greater  con- 
densing surface  than  if  they  had  passed 
directly  through  the  vat.  To  keep  the 
coil  of  pipe  cool,  the  vats  are  kept  filled 


FIG.  44. 


QUESTIONS.— What  is  distillation,  or  sublimation  ?    What  is  the  difference  between  a 
distillate  and  a  sublimate  ?    What  is  rectification  ?    How  is  distillation  effected  ? 


100  PRINCIPLES     OF     CHEMISTRY. 

With  cold  water.  In  Fig.  44,  a  is  a  furnace,  in  which  is  fixed  a  copper  ves- 
sel, or  still,  to  contain  the  liquid.  Heat  being  applied,  the  steam  rises  in  the 
head,  b,  and  passes  through  the  worm,  d,  which  is  placed  in  a  vessel  of  water, 
the  refrigerator.  The  vapor  thus  generated  is  condensed  in  its  passage,  and 
passes  out  as  a  liquid  by  the  external  pipe  into  a  receiver. 

156.  Drying   and    Distillation , — The  difference  between  drying 
by  heat  and  distillation  is,  that  in  one  case,  the  substance  vaporized,  being  of 
no  use,  is  allowed  to  escape  or  become  dissipated  in  the  atmosphene  ;  while 
in  the  other,  being  the  valuable  part,  it  is  caught  and  condensed  into  the 
liquid  form.     The  vapor  arising  from  damp  linen,  if  caught  and  condensed 
would  be  distilled  water ;  the  vapor  given  out  by  bread  while  baking,  would, 
if  collected,  be  a  spirit  like  that  obtained  in  the  distillation  of  grain. 

157.  Latent  Heat, — When  a  solid  is  converted  into  a 
liquid,  or  a  liquid  into  a  vapor  or  gas,  heat  in  large  quan- 
tity disappears,  and  ceases  for  the  time  to  a  fleet  the  ther- 
mometer.    It  is  not,  however,  absolutely  lost,  hut  remains 
incorporated  with  the  substance  of  the  liquid,  or  the  gas, 
in  an  insensible  condition.     Heat  thus  disappearing,  is 
termed  Latent,  or  Insensible  Heat. 

For  example,  if  a  thermometer  be  applied  to  a  mass  of  snow,  or  ice  just 
upon  the  point  of  melting,  it  will  be  found  to  stand  at  32°  F.  If  the  ice  be 
placed  in  a  vessel  over  a  fire,  and  the  temperature  tested  at  the  moment  it 
has  entirely  melted,  the  water  produced  will  have  only  the  temperature  of 
32°,  the  same  as  that  of  the  original  ice.  Heat,  however,  during  the  whole 
process  of  melting,  has  been  passing  rapidly  into  the  vessel  from  the  fire,  and 
if  a  quantity  of  mercury,  or  a  solid  of  the  same  size,  had  been  exposed  to 
the  same  amount  of  heat,  it  would  have  constantly  increased  in  temperature. 
It  is  clear,  therefore,  that  the  conversion  of  ice,  a  solid,  into  water,  a  liquid, 
has  been  attended  with  a  disappearance  of  heat. 

Again,  if  a  pound  of  water  at  212°  F.  be  mixed  with  a  pound  of  water 
at  33°  F.,  we  shall  obtain  two  pounds  of  water  at  122°,  a  temperature  ex- 
actly intermediate  between  the  temperature  of  the  two.  If,  however,  a 
pound  of  ice  at  32°,  is  mixed  with  a  pound  of  water  at  212°,  we  shall  ob- 
tain two  pounds  of  water,  of  which  the  temperature  is  only  51°.  In  this 
case  the  water  has  lost  161°,  while  the  ice  has  apparently  gained  but  19° ; 
so  that  142°  have  disappeared,  or  become  latent.  Thus,  in  order  to  convert 
a  pound  of  ice  at  32°  F.  into  water  at  33°,  as  much  heat  is  required  as  would 
bo  sufficient  to  raise  142  pounds  of  water  from  32°  to  33°  F.  Water,  there- 
fore, may  be  regarded  as  ice  in  combination  with  a  certain  quantity  of  heat. 


QXTESTIOXS. — What  is  the  difference  between  drying  by  heat  and  distillation  ?  What 
remarkable  circumstance  characterizes  the  phenomena  of  liquefaction  and  vaporization  ? 
Explain  what  is  meant  by  latent  heat  ?  What  experiments  prove  that  liquefaction  occa- 
sions a  disappearance  of  heat  ? 


THE     EFFECTS     O'F .    K  E'A;T;  *.  ;  ;'•     ;  ."lOl 

158.  Heat    required   to    Melt   Ice, — Some  idea  of  the  quantity 
of  heat  that  is  required  to  convert  ice  into  water,  without  any  apparent  rise 
in  temperature,  may  be  formed  from  the  iact  that  the  simple  conversion  of  a 
cube  of  ice,  three  feet  on  the  side,  into  water  at  32°,    would  absorb  the 
-whole  amount  of  heat  emitted  during  the  combustion  of  a  bushel  of  coal. 

159.  Disappearance   of   Heat    in    Vaporization In  the 

conversion  of  a  liquid  into  gas  or  vapor,  heat  disappears  to  a  much  greater 
extent  than  in  the  conversion  of  a  solid  into  a  liquid. 

The  absorption  of  heat  by  vaporization,  may  be  easily  rendered  perceptible 
to  the  feelings  by  pouring  a  few  drops  of  some  liquid  which  readily  evapo- 
rates, such  as  ether,  alcohol,  etc.,  upon  the  hand.  A  sensation  of  cold  is 
immediately  experienced,  because  the  hand  is  deprived  of  heat,  which  is 
drawn  away  to  effect  the  evaporation  of  the  liquid.  On  the  same  principle, 
inflammation  and'  ftverish  heat  in  the  head  may  be  allayed  by  bathing  the 
temples  with  any  liquid  which  evaporates  easily,  as  Cologne  water,  alcohol, 
vinegar,  etc. 

A  vessel  containing  water  placed  over  a  source  of  heat  which  is  tolerably 
uniform  in  temperature,  receives  equal  accessions  of  heat  in  equal  times. 
The  wat:T  at  first  rises  steadily  in  temperature,  and  at  212°  it  boils.  After 
this,  no  matter  how  much  the  heat  is  increased,  provided  the  steam  be  al- 
lowed to  escape  freely,  it  becomes  no  hotter ;  all  the  heat  which  is  added 
serving  only  to  convert  the  water  at  212°  into  steam  or  vapor. 

This  fact  is  of  considerable  importance  in  domestic  economy,  and  attention 
to  it  will  save  much  fuel  in  culinary  operations.  Soups,  etc.,  made  to  boil  in 
a  gentle  way  by  the  application  of  a  moderate  heat,  are  just  as  hot  as  when 
they  are  made  to  boil  over  a  strong  fire  with  the  greatest  violence.  "When  a 
liquid  is  once  brought  to  the  boiling  point,  the  fire  may  be  reduced,  as  a 
comparatively  small  quantity  of  heat  will  be  then  sufficient  to  maintain  it 
there. 

160.  Latent   Heat    of   Steam , — If  we  immerse  a  thermometer  in 
boiling  water,  it  stands  at  212° ;  if  we  place  it  in  steam  immediately  above  it, 
it  indicates  the  same  temperature.     The  question  then  arises,  what  becomes 
of  all  the  heat  which  is  communicated  to  the  water,  since  it  is  neither  indi- 
cated by  the  water  nor  by  the  steam  formed  from  it?     The  -answer  is,  that 
it  enters  into  the  water  and  converts  it  into  steam,  without  raising  its  tem- 
perature.    The  proof  that  steam  contains  more  heat  than  boiling  water,  is  to 
be  found  in  the  fact  that  if  we  mix  an  ounce  of  water  at  212°  with  five  and 
a  half  ounces  of  water  at  32°,  we  obtain  six  and  a  half  ounces  of  water  at 
a  temperature  of  about  60°  ;  but  if  we  mix  an  ounce  of  steam  at  212°  with, 

QTTKSTIONS. — What  is  the  comparative  quantity  of  heat  necessary  to  convert  ice  into 
water  ?  To  what  extent  is  heat  rendered  latent  by  vaporization  ?  What  experiments 
prove  that  heat  disappears  in  vaporization  ?  Do  liquids  acquire  additional  heat  after  at- 
taining a  boiling  temperature  ?  What  practical  application  can  be  made  of  this  principle 
in  domestic  economy  ?  What  is  the  sensible  heat  of  steam?  What  is  its  latent  heat? 
How  may  steam  at  212°  F.  be  proved  to  contain  more  heat  than  water  at  the  same  tem- 
perature ? 


102  PRINCIPLES    OF     CHEMISTRY. 

live  and  a  half  ounces  of  water  at  32°,  we  obtain  six  and  a  half  ounces  of 
water  at  212°.  The  steam,  from  which  the  increased  heat  is  all  derived, 
contains  as  much  more  heat  than  the  ounce  of  water  at  the  same  tempera- 
ture, as  would  be  necessary  to  raise  six  and  a  half  ounces  of  water  from  the 
temperature  of  60°  to  212°,  or  six  and  a  hah0  tunes  as  much  heat  as  would 
be  requisite  to  raise  one  ounce  of  water  through  about  152°  of  temperature. 
This  quantity  of  heat  will,  therefore,  be  found  by  multiplying  152°  by  six 
and  a  half,  which  will  give  a  product  of  983° — the  excess  of  heat  contained 
in  an  ounce  of  steam  at  212°  over  that  contained  in  an  ounce  of  boiling 
water  at  the  same  temperature. 

In  round  numbers,  therefore,  one  thousand  degrees  of  heat  are  absorbed 
in  the  conversion  of  water  into  steam,  and  this  constitutes  the  latent  heat 
of  steam. 

The  absorption  of  heat  in  the  process  by  which  liquids  are  converted  into 
vapor,  will  explain  why  a  vessel  containing  a  liquid  that  is  constantly  exposed 
to"  the  action  of  fire,  can  never  receive  such  a  degree  of  heat  as  would  de- 
stroy it.  A  tin  kettle  containing  water  may  be  exposed  to  the  action  of  the 
most  fierce  furnace,  and  remain  uninjured  ;  but  if  it  be  exposed,  without  con- 
taining water,  to  the  most  moderate  fire,  it  will  soon  be  destroyed.  The 
heat  which  the  fire  imparts  to  the  kettle  containing  water  is  immediately  ab- 
sorbed by  the  steam  into  which  the  water  is  converted.  So  long  as  water 
is  contained  in  the  vessel,  this  absorption  of  heat  will  continue ;  but  if  any 
part  of  the  vessel  not  containing  water  be  exposed  to  the  fire,  the  metal 
will  be  fused,  and  the  vessel  destroyed. 

161.  Effects  Produced  by  the  Absorption  of  Heat, — 
In  the  conversion  of  solids  into  liquids,  and  of  liquids  into  gases  or  vapors, 
the  heat  which  disappears  is  the  agent  by  which  liquefaction  in  the  one  case, 
and  vaporization  in  the  other,  are  produced ;  in  other  words,  the  absorption 
of  a  certain  amount  of  heat  is  necessary  for  the  production  of  the  change.  A 
liquid,  therefore,  may  be  regarded  as  a  compound  of  a  solid  and  heat,  and 
a  vapor  as  a  compound  of  heat  and  the  liquid  from  which  it  was  formed. 

162.  Freezing  Mixtures, — The  absorption  of  heat  con- 
sequent on  the  conversion  of  solids  into  liquids,  has  been 
taken  advantage  of  in  the  arts  for  the  production  of  ar- 
tificial cold  ;  and  the  compounds  of  different  substances 
which  are  made  for  this  purpose,  are  called  freezing  mix- 
tures. 

The  most  simple  freezing  mixture  is  snow  and  salt.  Salt  dissolved  in 
water  would  occasion  a  reduction  of  temperature,  but  when  the  chemical  re- 
lations of  two  solids  are  such,  that  both  by  mixing  are  rendered  liquid,  a  still 

QUESTIONS.— Why  does  a  kettle  containing  water  remain  uninjured,  when  exposed  to 
the  heat  of  a  fire  ?  What  may  be  considered  as  the  true  constitution  of  liquids  and  va- 
pors ?  What  are  freezing  mixtures  ?  Why  does  a  mixture  of  snow  and  salt  produce  a 
high  degree  of  cold  ? 


THE     EFFECTS     OF     HEAT.  103 

greater  degree  of  cold  is  produced.  Such  a  relation  exists  between  salt  and 
snow,  or  ice,  and  therefore  the  latter  substances  are  used  in  preference  to 
water.  When  the  two  are  mixed,  the  salt  causes  the  snow  to  melt  by  rea- 
son of  its  attraction  for  water,  and  the  water  formed  dissolves  the  salt:  so 
that  both  pass  from  the  solid  to  the  liquid  condition.  If  the  operation  is  so 
coniucted  that  no  heat  is  supplied  from  any  external  source,  it  follows  that 
the  heat  absorbed  in  liquefaction  must  be  obtained  from  the  salt  and  snow 
which  comprise  the  mixture,  and  they  must  therefore  suffer  a  depression  of 
temperature  proportional  to  the  heat  which  is  rendered  latent 

In  this  way  a  degree  of  cold  equal  to  40°  below  the  freezing  point  of  water 
may  be  obtained.  The  application  of  this  experiment  to  the  freezing  of 
ice-creams  is  familiar  to  all 

By  mixing  snow  and  sulphuric  acid  together  in  proper  proportions,  a  tem- 
perature of  from  70°  to  90°  below  zero  can  be  obtained  without  difficulty. 

A  very  convenient  process  for  freezing  water  without  the  use  of  ice  is  to 
drench  finely-powdered  sulphate  of  soda  with  the  undiluted  hydrochloric 
(muriatic)  acid  of  the  shops.  In  this  way  a  very  low  temperature  may  be 
readily  obtained.  The  vessel  in  which  the  mixture  is  made  becomes  cov- 
ered with  hoar  frost,  and  water  in  tubes  or  bottles  immersed  in  the  mixture, 
is  speedily  frozen, 

163.  Greatest    Artificial    Cold  — The  most  intense  artificial  cold 
is,  however,  produced  by  the  rapid  evaporation  of  highly  volatile  liquids,  such 
as  result  from  the  condensation  and  liquefaction  of  certain  gases.     By  means 
of  a  mixture  of  liquid  nitrous  oxyd  and  sulphuret  of  carbon,  placed  under  the 
exhausted  receiver  of  an  air-pump,  M.  Natterer  obtained  the  enormously  low 
temperature -of  two  hundred  and  twenty  degrees  below  zero. 

The  cold  produced  by  evaporation  is  due  to  the  absorption  of  heat  by  the 
newly-formed  vapor,  and  the  more  rapidly  evaporation  takes  place,  the  more 
rapidly  is  heat  abstracted  from  the  evaporating  liquid  and  from  surrounding 
substances. 

164.  Freezing   by    Evaporation  — Ether  may  be  made  to  evapo- 
rate so  rapidly  as  to  freeze  water,  even  in  summer.     This  may  be  illustrated 
by  filling  a  small  glass  tube  with  water,  and  surrounding  it  with  cotton,  or 
some  other  porous  substance,  soaked  in  ether.     If  a  current  of  air  be  then 
directed  upon  the  cotton  from  a  common  bellows,  the  ether  will  evaporate 
and  absorb  heat  so  rap- 
idly, as  to  convert  the  FIG.  45. 

water  into  ice  in  a  few  f 

minutes.  / 

165.  The      Cry- 
o  p  h '  o  -  r  u  s  — An    in- 
strument  known  as  the 

QUESTIONS. — By  what  process  may  water  be  frozen  in  summer  without  the  aid  of  ice? 
What  is  the  most  intense  artificial  cold  produced  ?  What  is  the  lowest  degree  of  tem- 
perature ever  observed  ?  To  what  is  the  cold  produced  by  evaporation  due  ?  How  may 
water  be  frozen  by  the  evaporation  of  ether  ?  Explain  the  action  of  the  cryophorua. 


104  PRINCIPLES    OF    CHEMISTRY. 

cryophorus,  or  frost-bearer,  strikingly  illustrates  the  production  of  cold  by 
evaporation.  It  consists  of  two  glass  bulbs  connected  by  a  tube,  and  contain- 
ing a  portion  of  water,  as  represented  in  Fig.  45.  The  air  is  first  expelled 
from  the  instrument  by  boiling  the  water  inclosed,  and  allowing  the  steam 
to-  escape  by  a  small  opening  at  the  extremity  of  the  little  projecting  tube,  & 
"While  the  instrument  is  entirely  filled  with  steam,  the  point  e  is  fused  by 
the  blow-pipe  flame,  and  the  opening  hermetically  closed.  In  experimenting 
with  this  instrument,  the  water  is  ah1  poured  into  one  bulbr  and  the  other,  or 
empty  bulb,  is  placed  in  a  basin  containing  a  mixture  of  ice  and  salt.  Tho 
vapor  in  the  eooted  bulb  ist  condensed,  but  its  place  is  immediately  supplied 
by  vapor  which  rises  into  the  dry  air  from  the  water  in  the  other  bulb.  JL 
rapid  evaporation,  therefore,  takes  place  in  the  water-bulb,  and  condensation 
in  the  empty  bulb,  until  by  reason,  of  the  condensation  and  rapid  evaporation, 
the  water  in  the  former  bulb  is  cooled  so  low  as  to  freeze, 

Prac-tieal  Illustrations  — A  shower  of  rain  cools  the  air  irt 
summer,  because  the  earth  and  the  air  both  part  with  their  heat  to  promote 
evaporation.  In  a  like  manner,,  the  .sprinkling  of  a  hot  room  with  water  cools 
it. 

The  danger  arising  from  wet  feet  and  clothes  is  owing  to  the  absorption  of 
heat  from  the  body  by  the  evaporation  from  the  surfaces  of  the  wet  materials  - 
the  temperature  of  the  body  is  in  this  way  reduced  below  its  natural  standard, 
and  the  proper  circulation!  of  the  blood  interrupted. 

The  evaporation,  which  takes,  place  continually  from  the  surface  of  the 
skin  and  the  cells  of  the  lungs  of  animals,  is  a  powerfully  cooling  agency,  and 
a  protection  against  external  heat.  When  the  heat  of  the  body  is  increased 
by  exercise,  or  by  exposure  to  high  temperatures,  perspiration  and  evapora- 
tion take  place  rapidly.  Heat  is  thereby  absorbed  and  rendered  latent  in. 
large  quantity,  and  a  healthy  temperature  of  the  system  maintained.  It  is 
on  this  principle  that  persons  are  enabled  to  expose  themselves  for  a  time 
to  an  atmosphere  of  very  high  temperature  without  serious  inconvenience, 
as  in  foundries,  boiler-rooms  of  steamers,  ovens  of  manufactories,  etc.  If, 
however,  the  air  be  moist,  or  the  surface  of  the  skin  be  varnished,  so  as  to* 
check  or  prevent  perspiration  and  evaporation,,  the  heat  can  only  be  sus- 
tained for  a  few  moments. 

The  air  hi  the  spring  of  the  year,  when  the  ice  and  snow  are  thawing, 
is  always  peculiarly  cold  and  chilly.  This  is  due  to  the  constant  absorption 
of  heat  from  the  air  by  the  ice  and  snow  in  their  transition  from  a  solid  to  a, 
liquid  state. 

166.  Conversion  of  Latent  into  Sensible  Heat, — When 
vapors  are  condensed  into  liquids,  and  liquids  are  changed 

QUESTIONS. — How  does  a  shower  of  rain  cool  the  air  and  the  earth  in  summer  ?  How- 
does  the  drainage  of  a  country  promote  its.  warmth  ?  From  what  does  the  danger  of  wet 
clothes  and  feet  arise  ?  How  does  perspiration  and  evaporation  from  the  surface  of  the 
skin  equalize  the  temperature  of  the  body  ?  Why  is  the  air  in  the  spring  of  the  year 
peculiarly  cold  and  chilly  ?  Under  what  circumstances  is  latent  converted  into  sensible 
heat? 


THE    EFFECTS    OF    HEAT.  105 

into  solids,  the  latent  heat  contained  in  them  is  set  free, 
or  made  sensible. 

If  water  be  taken  into  an  apartment  whose  temperature  is  several  degrees 
below  the  freezing  point,  and  allowed  to  congeal,  it  will  render  the  room  sen- 
sibly warmer.  It  is,  therefore,  in  accordance  with  this  principle  that  tubs  of 
water  are  allowed  to  freeze  in  cellars  in  order  to  prevent  excessive  cold. 

The  large  amount  of  heat  latent  in  water,  which  it  gives  forth  as  it  freezes, 
furnishes  a  source  of  heat  of  the  greatest  value  in  mitigating  the  severity  of 
winter,  and  in  rendering  the  transitions  of  atmospheric  temperature,  from  heat 
to  cold  and  from  cold  to  heat,  uniform  and  gradual. 

In  the  colder  regions,  every  ton  of  water  converted  into  ice  gives  out  and 
diffuses  in  the  surrounding  region  as  much  heat  as  would  raise  a  ton  of  water 
from  32°  to  174°  ;  and,  on  the  other  hand,  when  a  rise  of  temperature  takes 
place,  the  thawing  of  the  ice  absorbs  a  like  quantity  of  heat :  thus,  in  the  one 
ease,  supplying  heat  to  the  atmosphere  when  the  temperature  falls ;  and,  in 
the  other  absorbing  heat  from  it  when  the  temperature  rises. 

In  the  winter,  the  weather  generally  moderates  on  the  fall  of  snow ;  snow- 
is  frozen  water,  and  in  its  formation  heat  is  imparted  to  the  atmosphere,  and 
its  temperature  increased, 

Steam,  on  account  of  the  latent  heat  it  contains,  is  well  adapted  for  the 
Warming  of  buildings,  or  for  cooking.  In  passing  through  a  line  of  pipes,  of 
through  meat  and  vegetables,  it  is  condensed,  and  imparts  to  the  adjoining 
surfaces  nearly  1000*  of  the  latent  heat  which  it  contained  before  condensation. 

Steam  burns  much  more  severely  than  boiling  Water,  for  the  reason  that 
the  heat  it  imparts  to  any  surface  upon  which  it  is  condensed,  is  much  greater 
than  that  of  boiling  water, 

167.  Elastic  Force  of  Vapors,— All  vapors  are  elastic, 
like  air. 

The  tendency  of  vapors  to  expand  is  generally  consid- 
ered to  be  unlimited  ;  that  is  to  say,  the  smallest  quantity 
of  vapor  lias  a  tendency  to  diffuse  itself  through  every 
part  of  a  vacuum,  be  its  size  what  it  may,  exercising  a 
greater  or  less  degree  of  force  against  any  obstacle  which 
may  restrain  it. 

Eecent  researches  of  M.  Babinet,  a  French  physicist,  seem  to  show,  that  all 
gases  and  vapors  entirely  lose  their  elasticity  when  reduced  to  a  certain  de- 
gree of  tenuity,  and  that  no  gas  or  vapor,  formed  Under  the  ordinary  pressure 
of  the  atmosphere,  can  expand  sufficiently  to  fill  an  empty  space  20,000  times 
greater  than  the  original  volume  of  the  gag  or  vapor, 

QUESTIONS.— How  does  the  freezing  of  water  tend  to  elevate  the  temperature  of  the  sur- 
rounding atmosphere  ?  "Why  is  steam  well  adapted  for  the  warming  of  buildings  and 
for  cooking  ?  Why  does  steam  burn  more  severely  than  water  of  the  same  temperature  ? 
What  is  said  of  thS  elasticity  of  Vapors  ?  In  what  manner  do  Vapors  tend  to  expand  ? 

5* 


106  PRINCIPLES    OF    CHEMISTRY, 

The  force  with  which  a  vapor  expands  is  called  its  elastic 
force,  or  tension. 

The  elasticity  or  pressure  of  vapors  is  best  illustrated  in  the  case  of  steam, 
which  may  be  considered  as  the  type  of  all  vapors. 

168.  Expansive    Force    of   Steam  ,  —  When  a  quantity  of  pure 
Bteam  is  confined  in  a  close  vessel,  its  elastic  force  will  exert  on  every  part 
of  the  interior  of  the  vessel  a  certain  pressure  directed  outward,  having  a 
tendency  to  burst  the  vessel, 

"When  Bteam  is  generated  in  an  open  vessel  its  elastic  force  must  be  equal 
to  the  elastic  force  or  pressure  of  the  atmosphere  ;  otherwise  the  pressure  of 
the  air  would  prevent  it  from  forming  and  rising.  Steam,  therefore,  produced 
from  boiling  water  at  212°  F.,  is  capable  of  exerting  a  pressure  of  15  pounds 
upon  every  square  inch  of  surface,  of  one  ton  on  every  square  foot,  a  force 
equivalent  to  the  strength  of  600  horses, 

If  water  be  boiled  under  a  diminished  pressure,  and  therefore  at  a  lower 
temperature,  the  steam  which  is  produced  from  it  will  have  a  pressure  which 
is  diminished  in  an  equal  degree.  If,  on  the  contrary,  the  pressure  under 
Which  water  boils  be  increased,  the  boiling  temperature  of  the  Water  and  the 
pressure  of  the  steam  formed  will  be  increased  in  a  like  proportion,  We  have, 
therefore,  the  following  rule  •— 

Steam  raised  from  water,  boiling  under  any  given  pres- 
sure, has  an  elasticity  always  equal  to  the  pressure  under 
which  the  water  boils. 

Steam  of  a  high  elastic  force  can  only  be  made  in  close  vessels,  or  boilers. 
The  water  in  a  steam-boiler,  in  the  first  instance,  boils  at  212°,  but  the  steam 
thus  generated  being  prevented  from  escaping,  presses  on  the  surface  of  the 
water  equally  as  on  the  surface  of  the  boiler,  and  therefore  the  boiling  point 
Of  the  water  becomes  higher  and  higher  ;  or  in  other  words,  the  Water  has 
to  grow  constantly  hotter,  in  order  that  the  steam  may  form.  The  steam 
thus  formed  has  the  same  sensible  temperature  as  the  water  which  produces 
it, 

169.  Marcet's   Digester  .—The  above  principles  are  experimentally 
proved  by  means  of  an  apparatus  known  as  Marcet's  Digester.     This  con- 
sists of  a  stout  globular  vessel  of  iron,  Fig,  46,  into  which  a  portion  of  mer- 
cury is  poured,  and  then  water  sufficient  to  half  fill  it.     Into  the  top  of  the 
Vessel  a  long  glass  tube,  Z>,  is  tightly  fitted,  open  at  both  ends,  and  dipping 
into  the  mercury,     This  tube  is  provided  with  a  scale  divided  into  inches. 
The  globular  vessel  haa  also  two  other  openings,  into  one  of  which  a  stop- 


ioNB.-^What  is  the  force  with  Which  a  vapor  expands  turned  ?  In  what  manner 
will  steam  confined  in  a  close  vessel  exert  a  pressure  ?  What  is  the  pressure  of  steam 
generated  in  the  open  air  ?  What  rule  governs  the  elasticity  of  steam  ?  What  arrange- 
ments are  essential  to  the  production  of  steam  of  great  elastic  force  ?  What  relations  ex- 
ist between  the  temperature  6f  steam  formed  under  pressure  and  the  water  which  pro- 
duces it?  What  is  Marcet's  digester?  What  principles  may  be  experimentally  proved 
by  this  apparatus  ? 


THE    EFFECTS     OF     HEAT. 


107 


cock,  d,  is  screwed,  and  into  the  other  a  thermom- 
eter, c,  having  its  bulb  within  the  globe.  Heat  is 
applied  to  the  vessel,  and  the  water  made  to  boil.  So 
long  as  free  communication  with  the  atmosphere  is 
permitted  through  the  open  stop-cock  d,  the  tempera- 
ture of  ebullition,  as  indicated  by  the  thermometer,  c, 
continues  steady  at  212°,  and  the  steam  formed  exerts 
a  pressure  of  course  equal  to  one  atmosphere,  or  1 5  Ibs. 
to  the  square  inch.  On  shutting  the  stop-cock,  and 
continuing  the  heat,  the  temperature  of  the  interior 
rises  above  212°.  The  steam  in  the  upper  part  of  the 
vessel  becomes  denser,  and  as  fresh  portions  continue 
to  rise  from  the  water,  the  pressure  on  the  surface  of  c 
the  water  increases,  and  this  in  turn  pressing  upon  the 
mercury,  forces  it  to  ascend  in  the  tuba  Now  the 
height  of  the  mercurial  column  expresses  the  elastic 
force  or  pressure  of  the  steam  produced  in  the  boiler 
at  any  particular  temperature  above  212°.  Thus  the 


FIG.  46. 


weight  of  that  section  of  the  atmosphere  which  presses      jTTV     a 
upon  the  mercury  in  the  open  end  of  the  tube  is     ill 
equivalent  to  the  weight  of  a  column  of  mercury  of  jf 

30  inches ;  and  this  pressure  must  be  overcome  by  the  II 

steam  at  212°  before  it  can  commence  to  act  upon  the 

mercurial  guage  at  all.  For  every  thirty  inches  after  -this  that  the  mercury 
is  forced  up  into  the  tube  by  the  steam,  it  is  said  to  have  the  pressure,  or 
elastic  force  of  another  atmosphere.  Thus,  when  the  mercury  in  the  tube 
stands  at  30  inches,  the  steam  is  said  to  be  of  two  atmospheres;  at  45  inches, 
of  two  and  a  half;  at  €0  inches,  of  three  atmospheres,  and  so  on.  The  boil- 
ing point  of  the  water,  also,  as  shown  by  the  thermometer,  increases  with  the 
pressure  of  the  steam  upon  its  surface,  "When  the  mercury  stands  at  30 
inches,  or  when  the  pressure  on  the  water  is  equal  to  that  of  an  additional 
atmosphere,  the  thermometer  marks  a  temperature  of  249° ;  at  60  inches, 
•273° ;  at  90  inches,  or  with  a  pressure  of  four  atmospheres,  291°,  and  so  on. 
170.  Tables  of  the  Temperature  and  Pressure  of 
Steam . — As  the  relation  between  the  temperature  and  the  pressure  of 
steam,  and  the  varying  temperature  at  which  water  boils  or  gives  off  steam 
tinder  pressure,  are  matters  of  great  importance  in  connection  with  the  steam- 
engine,  the  French  government  many  years  ago  appointed  a  commission  of 
eminent  scientific  men  to  investigate  the  whole  subject.  The  result  of  their 
labors  has  been  embodied  in  a  series  of  tables,  which  show  at  once  the  pres- 
sure of  steam  formed  in  contact  with  water  at  any  given  temperature,  or  con- 
versely, the  temperature  at  any  given  pressura  It  was  thus  found  that  the 
temperature  of  steam  capable  of  exerting  a  pressure  of  twenty-  five  atmos- 


. — Under  what  circumstances 
pressure  of  steam  investigated? 


rere  the  relations  between  the  temperature  and 


108 


PRINCIPLES  OF  CHEMISTRY. 


FIG.  47. 


pheres,  or  375  pounds  upon  each  square  inch  of  boiler  surface,  was  43  9«. 
The  temperature  of  the  water  producing  steam  of  this  pressurej  must  have 
been  consequently  the  same. 

171.  Determination  of  Steam-press nre  in  Boilers. — 
The  application  of  these  principles  affords  a  ready  method  of  determining  the 
pressure  at  any  moment  which  steam  exerts  upon  the  interior  of  a  boiler,  or 
upon  the  piston  of  a  steam-engine.     Thus,  if  a  thermometer  inserted  into  a 
steam-boiler  indicates  a  temperature  of  212°  R,  we  know  that  the  steam  ex- 
erts a  pressure  of  one  atmosphere,  or  15  pounds  upon  a  square  inch;  if  the 
thermometer  stands  at  249°,  the  pressure  is  30  pounds  •  at  273°,  45  pounds  j 
and  so  on. 

172.  Barometer    Guag-e  , — The  degree  of  pressure  which  steam  ex- 
erts upon  the  interior  of  the  boiler  is,  however,  more  generally  determined  by 
the  height  to  which  a  column  of  mercury  is  elevated  and  sustained  by  such 
pressure.    The  instrument  employed  for  this  purpose  is  termed  a  "  steam"  or . 

"barometer  guage."  It  consists  simply 
of  a  bent  tube,  A,  C,  D,  E,  Fig.  47,  fitted 
into  the  boiler  at  one  end,  and  open  to 
the  air  at  the  other.  The  lower  part  of 
the  bend  of  the  tube  contains  mercury, 
which,  when  the  pressure  of  steam  in 
the  boiler  is  equal  to  that  of  the  external 
atmosphere,  will  stand  at  the  same  levelT 
H,  R,  in  both  legs  of  the  tube.  When 
the  pressure  of  the  steam  is  greater  than 
that  of  the  atmosphere,  the  mercury  is 
depressed  in  the  leg  C  D,  and  elevated  in 
the  leg  D  El  A  scale,  G,  is  attached  to 
the  long-  arm  of  the  tube,  and  by  observ- 
ing the  difference  of  the  levels  of  the  mer- 
cury in  the  two  tubes,  the  pressure  of  the  steam  may  be  calculated.  Thusr 
when  the  mercury  is  at  the  same  level  in  both  legs,  the  pressure  of  the 
steam  balances  the  pressure  of  the  atmosphere,  and  is  therefore  15  pounds 
per  square  inch.  If  the  mercury  stands  30  inches  higher  in  the  long  arm 
of  the  tube,  then  the  pressure  of  the  steam  is  equal  to  that  of  two  atmos- 
pheres, or  is  30  pounds  to  the  square  inch,  and  so  on. 

173.  Varying  Conditions   of  Steam-pressure  • — It  is  to  be 
understood  that  the  relations  between  the  pressure  of  steam  and  its  tempera- 
ture which  have  been  pointed  out,  exist  only  when  the  steam  is  in  contact 
with  a  body  of  water  from  which  fresh  steam  is  constantly  rising,  as  in  an. 
ordinary  steam-boiler.     Under  such  circumstances,  the  elasticity,  or  expansive, 
force  of  the  steamr  increases  rapidly  with  its  increase  in  temperature;.  but  in 

QUESTIONS How  may  the  pressure  of  steam  upon  the  interior  of  a  boiler  be  deter- 
mined by  means  of  the  thermometer?  What  is  a  barometer  guage?  Under  what  cir- 
cumstances do  the  relations  which  havB  been  pointed"  out  between  the  pressure  of  steam 
and  its  temperature  exist  ?  In  what  manner  does  steam  heated  apart  from  water  expand  ? 


THE     EFFECTS     OF     HEAT.  109 

a  greater  degree  by  equal  additions  of  heat  at  high,  than  at  low  temperatures. 
Ifj  however,  the  steam  is  heated  apart  from  water,  it  follows  the  law  that 
regulates  the  expansion  of  all  gaseous  bodies,  viz.,  that  equal  increments  of 
heat  expand  it  equally  at  all  temperatures — this  expansion  being  equal  to 
l-490th  of  its  volume  at  32°  F,  for  every  additional  degree  of  heat  imparted  to 
it.* 

174.  Higli-pre&sure  Steam,— Steam  generated  by  water 
boiling  at  a  very  high  temperature,  is  known  as  high- 
pressure  steam.  By  this  we  mean  steam  condensed,  not 
by  the  withdrawal  of  heat,  but  by  pressure,  just  as  high- 
pressure  air  is  merely  condensed  air.  To  obtain  double, 

*  Some  very  curious  experiments  which  have  heen  made  from  time  to  time,  seem  to 
show  that  steam  and  other  vapors,  when  subjected  to  extraordinary  pressure,  do  not  con- 
tinue to  expand  with  additions  of  heat,  but  actually  contract.  The  first  information  which 
was  obtained  in  relation  to  this  subject  was  from  a  very  dangerous  experiment  tried  many 
years  since  in  England.  A  measured  quantity  of  water  was  placed  in  a  boiler,  with  all 
the  safety-valves  most  carefully  closed,  and  every  chance  for  the  escape  of  steam  pre- 
vented. The  fire  was  now  got  up,  and  for  some  time  the  steam-guage,  as  usual,  indicated 
a  regularly  increasing  pressure.  At  length,  however,  to  the  surprise  of  all,  the  pressure 
was  seen  slowly  but  gradually  to  diminish,  and  although  the  boiler-plates  became  nearly 
red-hot,  this  remarkable  phenomenon  continued,  and  when  the  boiler  had  cooled,  It  was 
found  that  no  water  had  escaped. 

The  experiment  was  afterward  repeated  by  De  Ja  Tour,  a  French  chemist,  in  a  different 
manner  with  similar  results.  He  partially  filled  some  very  strong  glass  tubes  with  water, 
alcohol,  ether,  and  some  other  liquids,  furnished  them  with  guages,  and  hermetically 
sealed  them.  The  tubes  were  then  gradually  exposed  to  heat,  until  the  contained  liquids 
vaporized,  and  as  true  steam  became  transparent,  or  invisible.  Under  these  circum- 
stances, the  law  "that  the  elasticity  or  expansive  force  of  vapors  augments  with  every  ad- 
ditional increase  of  temperature,"  was  not  found  to  hold  good,  and  the  following  result* 
were  obtained : 

All  the  liquids,  by  reason  of  the  enormous  pressure  which  the  vapor  gradually  formed 
from  them  exerted  upon  their  surfaces,  required  to  be  elevated  to  a  high  degree  of  tem- 
perature before  complete  vaporization  took  place.  Ether,  which  passes  into  vapor  in  the 
open  air  at  a  temperature  of  96°  F.,  only  became  vapor  at  328°,  in  a  space  equal  to 
double  its  original  bulk !  At  this  temperature  its  vapor  should,  according  to  the  recog- 
nized law  of  expansion,  have  exerted  a  pressure  of  209  atmospheres,  or  more  than  3,000 
pounds  per  square  inch  •  it,  however,  exerted  a  pressure  of  only  37  atmospheres,  or  555 
pounds  per  square  inch.  Alcohol,  which  occupied  2-8ths  the  capacity  of  its  tube,  gradu- 
ally expanded  to  double  its  volume,  and  then  suddenly  disappeared  in  vapor,  at  a  tem- 
perature of  404°  F.  ;  its  calculated  pressure  was  3,  GOO  pounds  per  square  inch  ;  its  real 
pressure  was  only  1,700  pounds.  Water  was  found  to-  become  vapor  in  a  space  equal  to 
about  four  times  its  original  bulk,  at  a  temperature  of  about  773°.  At  this  temperature 
its  solvent  power  was  so  greatly  increased,  that  it  acted  most  powerfully  upon  the  glass 
and  broke  it,  and  it  was  found  necessary  to  add  carbonate  of  soda  to  the  water  to  diminish 
its  action.  As  the  vapors  in  the  tubes  cooled,  a  point  was  observed  at  which  a  sort  of 
cloud  filled  the  tube,  and  in  a  few  moments  after,  the  liquid  suddenly  re-appeared. 

In  explanation  of  the  diminished  pressure  which  vapors  of  high  temperature  exert  tin- 
der the  above-mentioned  conditions,  it  has  been  suggested  that  their  particles,  by  reason 
of  their  forced  and  close  contiguity,  are  partially  controlled  by  a  force  of  cohesion,  which 
in  part  neutralizes  the-  expansive  force  imparted  by  the  heat. 

QUESTION.— Wh at  is  high-pressure  steam  ! 


110  PRINCIPLES     OF     CHEMISTRY. 

triple,  or  greater  pressure  of  steam,  we  must  have  twice, 
thrice,  or  more  steam  under  the  same  volume. 

175.  Super- heated  Steam, — Steam  which  has  been  heated 
in  a  separate  state  to  a  high  degree  of  temperature  is 
known  as  super-heated  steam.     In  this  condition  it  is  em- 
ployed for  the  production  of  effects  not  attainable  by  the 
use  of  ordinary  steam  ;  such  as  the  distillation  of  oils, 
the  carbonization  of  wood,  etc. 

In  some  of  the  processes  recently  introduced  for  the  distillations  of  oils  by 
the  use  of  super-heated  steam,  the  temperature  of  the  steam  is  elevated  to  a 
sufficient  degree  to  melt  lead.  To  effect  the  carbonization  of  wood,  steam  is 
elevated  to  a  high  degree  of  temperature  by  passage  through  red-hot  pipes. 
It  is  then  allowed  to  enter  a  vessel  containing  wood  which  is  intended  to  be 
converted  into  charcoal  The  heated  steam  penetrating  into  the  pores  of 
the  wood,  drives  off  the  volatile  portions,  the  water,  tar,  etc.,  and  leaves  tho 
pure  carbon  behind. 

In  the  manufacture  of  lard  on  an  extensive  scale,  the  carcase  of  the  whole 
hog  is  exposed  to  the  action  of  steam  at  a  very  high  pressure  and  tempera- 
ture. This  acting  upon  the  mass  of  flesh,  breaks  up  and  reduces  the  whole 
to  a  fat  fluid  mass,  leaving  the  bones  in  the  state  of  powder.  Steam  of  or- 
dinary pressure  and  temperature,  under  the  same  circumstances,  would  pro- 
duce this  effect. 

176.  Vapor  produced  by  different  Liquids, — Equal  bulks 
of  different  liquids  raised  to  their  respective  boiling  points, 
produce  very  different  quantities  of  vapor. 

"Water  furnishes,  bulk  for  bulk,  a  much  larger  amount  of  vapor  than  any 
other  liquid;  a  cubic  inch  of  water  at  its  ordinary  boiling  point,  212°,  ex- 
panding to  nearly  a  cubic  foot  of  steam  at  212°,  or  to  about  1700  times  its 
volume ;  a  cubic  inch  of  alcohol,  on  the  other  hand,  at  its  ordinary  boiling 
temperature,  expands  only  528  times  its  volume;  ether  to  298;  and  oil  of 
turpentine  to  193. 

177.  Ratio  between  Sensible  and  Latent   Heat. — The 
sum  of  the  sensible  heat  of  steam,  and  the  amount  of 
latent  heat  contained  in  it,  are  always  the  same,  since  the 
latent  heat  of  steam  diminishes  exactly  in  proportion  as 
its  sensible  heat  rises. 

Water  may  be  easily  made  to  boil  in  a  vacuum  at  the  temperature  of  100°, 

QUESTIONS. — What  is  super-heated  steam  ?  For  what  purposes  is  it  applied  ?  How  can 
wood  be  carbonized  by  the  use  of  steam  ?  How  is  high-pressure  steam  employed  in  the 
manufacture  of  lard?  Is  the  quantity  of  vapor  produced  from  equal  bulks  of  liquid  the 
same  ?  What  are  illustrations  of  this  ?  What  ratio  exists  between  the  sensible  and  lat- 
ent heat  of  steam?  Is  there  any  economy  in  evaporating  water  at  a  low  temperature  and 
under  diminished  pressure  ? 


THE    EFFECTS     OF     HEAT.  Ill 

but  the  steam  generated  is  much  less  dense  than  that  produced  at  212° 
and  has  a  greater  latent  heat.  If  water  boils  at  312°,  the  amount  of  heat 
absorbed  (rendered  latent)  in  vaporization,  will  bo  less  by  100°  than  if  it  had 
boiled  at  212° ;  and,  on  the  contrary,  if  water  bo  boiled  under  a  diminished 
pressure,  at  112°,  the  heat  absorbed  in  vaporization  will  bo  100°  more  than 
if  it  had  boiled  at  212°,  Hence  there  can  be  no  economy  of  heat  iu  distilling 
in  vacuo, 

The  sum  of  the  sensible  and  latent  heat  of  steam  being  always  the  same, 
1184°,  Wo  may  very  readily  ascertain  the  latent  heat  of  steam  at  any  tempe- 
rature, by  subtracting  its  sensible  heat  from  this  constant  number.  For  ex- 
ample, steam  at  280°  has  a  latent  heat  of  904°  (1184  —  280—904) ;  so  also 
Bteam  at  100°  has  1084°  of  latent  heat 

The  theory  of  latent  heat,  and  the  principles  which  govern  the  formation, 
expansion,  and  condensation  of  vapors,  are  practically  applied  in  the  working 
of  the  steam-engine,  and  in  many  industrial  operations.  A  further  considera- 
tion of  them  is,  however,  foreign  to  the  object  of  this  work. 

178.  Liquefaction  of  Gases, — Gases  were  formerly  con- 
sidered to  be  essentially  different  in  their  nature  from  va- 
pors, but  comparatively  recent  experiments  have  shown 
that  their  constitution  is  similar,  and  is  owing  to  the  latent 
heat  they  contain. 

Faraday  demonstrated  the  possibilit}*,  by  the  joint  action  of  cold  and  great 
pressure,  of  reducing  several  of  the  so-called  permanent  gases  to  the  liquid 
and  even  to  the  solid  Istate. 

The  method  employed  by  him  was  FIG.  48. 

to  generate  the  gas  from  materials 
placed  in  one  end  of  a  strong  glass 
tube,  bent  in  the  middle,  and  her* 
metically  sealed,  as  represented  in 
Fig.  48,  The  gas,  accumulating  in  a 
confined  space,  exerts  an  enormous  pressure  in  virtue  of  its  expansive  force ; 
the  effect  of  which  is,  that  a  portion  of  the  gas  itself  condenses  into  a  liquid 
in  the  end  of  the  tube  most  remote  from  the  materials,  which  is  kept  cool  by 
immersion  in  a  freezing  mixture  This  experiment  is  a  somewhat  hazardous 
one,  from  the  liability  of  the  tube  to  burst  under  the  pressure  exerted,  and  the 
hands  and  face  of  the  operator  should  always  be  protected  by  gloves  and  a 
mask  of  wire  gauze.  In  this  way  chlorine,  cyanogen,  carbonic  acid,  and  sev- 
eral other  gases,  may  be  liquefied. 

By  means  of  an  apparatus  of  different  construction,  but  involving  the  same 
principle,  carbonic  acid  gas  can  be  liquefied  and  solidified  in  large  quantities. 
The  details  of  this  process  will  be  described  under  the  chemical  consideration 
of  this  substance. 


QUESTIONS.—  How  may  the  latent  heat  of  steam  be  calculated?  To  -what  do  gases 
and  vapors  undoubtedly  owe  their  constitution?  Who  first  liquefied  gases?  By  what 
means  ^ras  this  accomplished  ?  What  gases  were  thus  liquefied  ? 


112  PRINCIPLES    OF    CHEMISTRY. 

Some  of  the  gases  are  liquefiable  with  much  greater  facility  than  others,  and 
a  few  assume  a  liquid  or  solid  form  by  the  mere  application  of  cold,  as  sul- 
.phurous  acid  gas.  Others  have  resisted  all  attempts  to  reduce  them  to  a 
liquid  state  by  subjection  to  immense  pressure  aided  by  the  greatest  artificial 
cold.  Among  these  are  oxygen,  hydrogen,  nitrogen,  carbonic  oxyd,  coal  gas, 
etc.  Oxygen  remained  gaseous  under  a  pressure  of  over  900  pounds  to  the 
square  inch,  and  at  a  temperature  of  140°  below  zero, 

179.  Absorption  of  Gases  by  Water . — All  gases  are  absorbed 
or  condensed  by  water  in  a  greater  or  less  degree,  in  which  case  they  must 
certainly  assume  the  liquid  form.  The  quantity  absorbed  is  very  different  for 
different  gases ;  and  in  the  same  gas  the  quantity  absorbed  depends  upon  the 
pressure  to  which  the  gas  is  subjected,  and  the  temperature  of  the  water. 
The  colder  the  water,  the  greater  the  quantity  of  the  gaa  taken  up  and  re- 
tained by  it,  '"  Jj>  . 


CHAPTER    III. 

LIGHT. 

180.  Light  and  its  Chemical  Relations, — The  general 
consideration  of  the  laws  of  light  heiongs  to  the  science  of 
Optics,  a  department  of  Natural  Philosophy.     Light,  how- 
ever, is  an  important  agent  in  producing  chemical  changes, 
especially  in  the  organized  forms  of  matter  ;  while  the 
physical  characters  of  an  object,  revealed  by  the  mere  me- 
chanical action  of  light  on  its  structure,  are  often  of  the 
greatest  chemical  value. 

A  brief  reference  to  some  of  the  more  important  laws  and.  physical  prop- 
erties of  light,  constitutes  a  proper  introduction  and  preparation  for  the  study 
of  its  chemical  effects. 

SECTION    I. 

'NATtf&E    AND    SOURCES    OF1    LIGHT. 

181.  Nature  of  Light,— Of  the  real  nature  of  light  we 
know  nothing.     Two  theories  or  hypothesis,  however,  have 
been  proposed  to  account  for  its  phenomena,  which  are 

QUESTIONS.— Are  all  gases  reduced  Witlt  equal  facility?  What  gaseS  ha^e  resisted  all 
attempts  to  liquefy  them  ?  What  is  said  of  the  absorption  of  gases  fry  water  ?  What 
connection  is  there  between  light  and  chemistry  ?  What  do  we  know  respecting  the  real 
nature  of  light  ? 


NATURE     AND     SOURCES     OF    LIGHT.         113 

known  as  the  Corpuscular,  or  Emission  theory,  and  the 
Uriel ulatoiy  theory. 

182.  The  Corpuscular  Theory  supposes,  the  sensation  of 
light  to  be  occasioned  by  the  transmission  of  particles  of 
a  refined  species  of  matter  from  the  luminous  body  to  the 
eye. 

According  to  this  theory,  there  is  a  striking  analogy  or  resemblance  be- 
tween the  eye  and  the  organs  of  smelling.  Thus,  we  recognize  the  odor  of 
an  object  in  consequence  of  the  material  particles  which  pass  from  the  object 
to  the  organs  of  smelling,  and  there  produce  a  sensation.  In  the  same 
manner,  a  visible  object  at  any  distance  may  be  supposed  to  send  forth  parti- 
cles of  light,  which  move  to  the  eye  and  produce  vision,  by  acting  mechan- 
ically on  its  nervous  structure,  as  the  odoriferous  particles  of  a  rose  produce  a 
sensible  effect  upon  the  organs  of  smell. 

183.  The  Undulatory  Theory  supposes  that  all  space, 
and  the  interstices  of  all  material  objects,  are  pervaded  by 
an  elastic   medium,   or  ether,  of  inconceivable   tenuity. 
This  medium  is  not  light  itself,  but  is  susceptible  of  being 
thrown  into  vibrations  or  undulations  by  impulses  inces- 
santly emanating  from  all  luminous  bodies.     These,  reach- 
ing the  eye,  affect  the  optic  nerve,  and  produce  the  sen- 
sation which  we  call  light. 

According  to  this  theory,  there  is  a  striking  analogy  between  the  eye  and. 
the  ear ;  the  vibrations,  or  undulations  of  the  ethereal  medium  being  supposed 
to  pass  along  the  space  intervening  between  the  visible  object  and  the  eye,  in 
the  same  manner  as  the  undulations  of  the  air,  produced  by  a  sounding  body, 
are  transmitted  to  the  ear. 

The  corpuscular  theory  was  sustained  by  Newton,  and  was  for  a  long  time 
generally  believed.  Since  the  commencement  of  the  present  century,  how- 
ever, it  has  been  gradually  losing  ground,  and  recent  experiments  instituted 
by  MM.  Foucault  and  Fizeau,  of  France,  conclusively  demonstrate  its  incor- 
rectness. It  is  now,  therefore,  entirely  discarded  by  all  the  leading  scientific 
authorities,  and  the  undulatory  theory  is  received  as  substantially  correct — 
since  it  affords  the  most  complete  explanation  of  the  facts  upon  which  the 
science  of  optics  is  based.  The  language,  however,  which  is  generally  em- 
ployed in  describing  optical  phenomena  is  for  the  most  part  framed  in  ac- 
cordance with  the  corpuscular  theory. 

184.  Sources  of  Light. — The  great  natural  sources  of 

QUESTIONS.— Explain  the  corpuscular  theory  of  light.  What  analogy  does  this  theory 
present?  Explain  the  undulatory  theory.  Wh.it  analogy,  according  to  this  theory,  exists 
between  the  eye  and  the  ear  ?  Which  theory  is  generally  received  ?  What  are  the  sources 
of  light  ? 


114  PRINCIPLES     OF     CHEMISTRY. 

light  are  the   sun  and  the  heavenly  bodies. .   All  bodies 
when  heated  to  a  sufficient  degree  become  luminous. 

All  solid  bodies  begin  to  emit  light  in  the  daytime  at  the  same  temperature, 
viz.,  977°  of  Fahrenheit's  thermometer.  As  the  temperature  rises,  the  bril- 
liancy of  the  light  rapidly  increases,  so  that  at  a  temperature  of  2600°  it  is 
almost  forty  times  as  intense  as  at  1900°.  Gases  must  be  heated  to  a  much 
greater  extent  before  they  begin  to  emit  light. 

185.  Electric  Light,— The  most  splendid  artificial  light 
known  is  developed  through  the  agency  of  electricity. 

The  electric  light,  so-called,  is  produced  by  fixing  pieces  of  pointed  char- 
coal to  the  wires  connected  with  opposite  poles  of  a  powerful  galvanic  bat- 
tery, and  bringing  them  within  a  short  distance  of  each  other.  The  space 
between  the  points  is  occupied  by  an  arch  of  flame  that  nearly  equals  in  daz- 
zling brightness  the  rays  of  the  sun. 

186.  Phosphorescence . — The  term  phosphorescence  is  applied  to 
that  property  which  various  bodies  possess  of  emitting  a  feeble  light  at  ordi- 
nary, or  low  temperatures. 

Phosphorescence  was  formerly  supposed  to  be  due  to  the  presence  of  phos- 
phorus (an  elementary  substance  which  emits  light  in  the  dark).  Hence  the 
origin  of  the  name.  The  phenomenon  is  now  known  to  proceed  from  other 
agencies. 

A  great  number  of  bodies  possess  the  property  of  shining  in  the  dark  when 
they  have  been  previously  exposed  to  the  light  of  the  sun.  Oyster  shells 
which  have  been  ignited  and  cooled,  especially  exhibit  phosphorescence. 
Among  other  substances  which  are  often  luminous  in  the  dark,  are  white 
paper  (especially  when  it  has  been  heated  nearly  to  burning),  egg-shells, 
corals,  bones,  ivory,  leather,  and  the  skins  of  men  and  animals.  The  cause 
of  this  phenomenon  is,  probably,  that  the  bodies  by  being  exposed  to  light, 
absorb  a  portion  of  it  unaltered  into  their  substance  by  adhesion,  and  subse- 
quently give  it  out  in  a  dark  place. — GMELIN. 

The  phenomenon  of  phosphorescence  occurs  in  the  most  marked  degree 
in  living  organized  bodies.  The  glow-worms,  and  several  species  of  flies  and 
beetles,  have  the  power  of  emitting  from  their  bodies  a  beautiful  pale,  bluish 
•white  light  The  great  lantern-fly  of  South  America  is  especially  brilliant — 
a  single  insect  affording  sufficient  light  to  enable  a  person  to  read.  The 
appearance  of  vast  luminous  tracts  in  the  sea,  at  night,  is  a  well-known  phe- 
nomenon. This  was  formerly  ascribed  to  the  motion  of  the  waves,  to  elec- 
tricity, or  to  the  formation  of  gases  containing  phosphorus,  through  the  pu- 
trefaction of  marine  animals ;  but  it  is  now  generally -believed  to  be  duo  to 
the  presence  of  an  immense  number  of  phosphorescent  animalculae. 

QTHEBTIONS — At  what  temperature  do  solids  become  luminous?  How  is  the  most  splen- 
did artificial  light  produced  ?  What  is  phosphorescence  ?  Under  what  circumstances  do 
bodies  often  become  luminous  ?  How  is  the  phenomenon  accounted  for  ?  What  substances 
exhibit  phosphorescence  in  the  most  marked  degree  ?  What  are  remarkable  instances 
of  phosphorescence  in  the  animal  kingdom  ?  To  what  is  the  luminous  appearance  of  tho 
sea  due? 


NATURE     AND     SOURCES     OF    LIGHT.         115 

Sea-fish,  in  general,  soon  after  death  exhibit  a  luminous  appearance,  par- 
ticularly the  herring  and  the  mackerel.  The  light  is  most  intense  before 
putrefaction  commences,  and  gradually  disappears  as  decomposition  proceeds. 
In  order  to  observe  the  phenomenon  more  distinctly,  the  fish  should  be  gut- 
ted, and  the  roes  and  scales  removed.  By  placing  such  luminous  fish  also 
in  weak  saline  solutions,  such  as  those  of  Epsom  salts  or  common  salt,  the 
solutions  even  become  luminous,  and  the  appearance  continues  for  some  days ; 
it  is  particularly  noticeable  when  the  liquids  are  agitated.  The  light  is  quickly 
extinguished  by  the  addition  of  pure  water,  of  lime  water,  and  by  acids  in 
general. 

The  decay  of  wood,  when  the  temperature  ia  moderate  and  moisture  and 
a  small  quantity  of  air  are  present,  is  frequently  attended  with  an  evolution 
of  light.  Wood  exhibiting  this  appearance  is  familiarly  known  as  "  light 
wood,"  and  is  of  a  white  appearance.  When  wood  decays  in  the  presence  of 
much  moisture  and  a  free  access  of  air,  it  is  reduced  to  a  brown  pulverulent 
mass  which  is  not  luminous.  The  phosphorescence  of  wood  ceases  when  the- 
temperature  falls  as  low  as  42°  F.,  and  it  is  also  irrecoverably  destroyed  by 
the  action  of  boiling  water. 

The  cause  of  phosphorescence  is  not  fully  understood ;  it  is,  however,  be- 
lieved to  be  the  result  of  a  chemical  action  between  the  oxygen  of  tho  air, 
or  water,  and  the  so-called  phosphorescent  matter,  This  matter  is  capable 
of  separation  from  the  living  animal,  and  is  characterized  by  a  remarkable  and 
disagreeable  odor. 

Light  is  also  developed,  under  certain  circumstances,  in 
the  act  of  crystallization. 

If  the  process  of  crystallizing  certain  substances  be  watched  in  a  darkened 
room,  the  separation  of  each  crystal  will  be  observed  to  be  accompanied  with 
a  faint  flash  of  light. 

SECTION    II. 

PROPERTIES    OF    LIGHT. 

187.  PropagationofLight , — Light,  from  whatever  source 
it  may  be  derived,  moves,  or  is  propagated  in  straight 
lines,  or  rays,  so  long  as  the  medium  traversed  is  uniform. 

By  a  medium,  we  mean  the  space  or  substance  through  which  light  passes. 
In  taking  aim  with  a  gun  or  arrow,  we  proceed  upon  the  supposition  that 
light  moves  in  straight  lines,  and  try  to  make  the  projectile  go  to  the  desired 
object  as  nearly  as  possible  by  the  path  along  which  the  light  comes  from  the 
object  to  the  eye. 

QUESTIONS.— What  circumstances  attend  the  decomposition  of  sea-fish  ?  What  is  said 
of  the  Iuminosit7  of  decayed  wood?  What  is  the  supposed  cause  of  phosphorescence? 
Is  light  ever  developed  by  the  act  of  crystallization  ?  In  what  manner  is  light  propagated  ? 


116  PRINCIPLES     OF     CHEMISTRY. 

Thus,  in  Fig.  49,  the  line  A  B,  which  represents  the  line  of  sight,  is  also 
the  direction  of  a  line  of  light  passing  in  a  perfectly  straight  direction  from  the 
object  aimed  at  to  the  eye  of  the  marksman. 

FIG.  49. 


188.  Divergence  of  Light, — Kays  of  light  proceeding  from 
a  luminous  body  diverge,  or  spread  out  from  one  another 
in  every  direction. 

189.  Law  of  Diminution  of  Light  by  Distance,— When 
light  diverges  from  a  luminous  center,  its  intensity  dimin- 
ishes, not  according  to  the  distance,  but  as  the  square  of 
the  distance.* 

Thus,  at  a  distance  of  two  feet,  the  intensity  of  light  will  be  one  fourth  of 
what  it  is  at  one  foot ;  at  three  feet  the  intensity  will  be  one  ninth  of  what  it 
is  at  one  foot.  In  other  words,  the  amount  of  illumination  at  the  distance  of 
one  foot  from  a  single  candle  would  be  the  same  as  that  from  four,  or  nine 
candles  at  a  distance  of  two,  or  three  feet,  the  numbers  four  and  nine  being 
the  square  of  the  distances  two,  and  three,  from  the  center  of  illumination. 

190.  Velocity  of  Light,— Light  does  not  pass  instanta- 
neously through  space,  but  requires  for  its  passage  from 
one  point  to  another  a  certain  interval  of  time. 

The  velocity  of  light  is  at  the  rate  of  about  one  hun- 
dred and  ninety-two  thousand  miles  in  a  second  of  time. 

191.  Action  of  Light  on  Matter, — When  light  falls  upon 
any  object,  it  may  be  disposed  of  in  three  ways  ;  1st,  it 
may  be  bent  back,  or  reflected  ;  2d,  it  may  be  absorbed 
into  the  substance  of  the  body,  and  disappear  ;  or  3d,  it 
may  be  transmitted,  or  pass  through  the  body. 


*  It  is  an  exceedingly  curious  fact,  that  this  law  of  the  variation  of  influence  according 
to  the  square  of  the  distance,  applies  to  all  physical  forces  which  spread  or  radiate  from  a 
center,  such  as  gravitation,  heat,  light,  electricity,  magnetism,  and  sound. 

QUESTIONS. — What  is  meant  hy  the  divergence  of  light  ?  How  does  the  intensity  of 
light  diminish  by  distance  ?  Illustrate  this  law.  What  is  the  velocity  of  light  ?  How  is 
light  falling  upon  the  surface  of  a  body  disposed  of  ? 


PKOPERTIES     OF    LIGHT.  117 

When  the  portion  of  light  reflected  from  any  surface,  or 
point  of  a  surface,  to  the  eye  is  considerable,  such  surface, 
or  point,  appears  white  ;  when  very  little  is  reflected,  it 
appears  dark-colored  ;  but  when  all,  or  nearly  all  the  rays 
are  absorbed,  and  none  are  reflected  back  to  the  eye,  the 
surface  appears  black. 

192.  Transparent   and  Opaque  Bodies, — Bodies  which 
allow  the  light  which  falls  upon  their  surfaces  to  pass 
through  them,  are  said  to  be  transparent ;  while  those 
which  prevent  its  passage  are  said  to  be  opaque. 

193.  Luminous  Bodies  are  those  which  shine  by  their 
own  light ;  such,  for  example,  as  the  sun,  the  flame  of  a 
candle,  metal  rendered  red  hot,  etc. 

All  bodies  not  in  themselves  luminous,  become  visible 
by  reflecting  the  rays  of  light. 

194.  Law  of  Reflection  of  Light, — The  law  which  gov- 
erns the  reflection  of  light  is  exceedingly  simple,  and  is 
the  same  as  that  which  governs  the  motion  of  an  elastic 
body  thrown  against  a  hard,  smooth  surface.     If  the  light 
falls  perpendicularly  upon  a  flat  surface,  it  is  turned  back, 
or  reflected  perpendicularly,  and  in  the  same  lines ;  if  it 
falls  obliquely,  it  is  reflected  obliquely,  the  angle  of  in- 
cidence being  equal  to  the  angle  of  reflection. 

Thus,  in  Fig.  50,  let  A  B  represent  the  direction  of  an  incident  ray  of  light 
falling  on  a  mirror,  F  C.  It  will  be  reflected  in  the  direction  B  E.  If  we 
draw  a  line,  D  B,  perpendicular  to  the  surface  of  the  mirror,  at  the  point  of 
reflection,  B,  it  will  be  found  that  the 
angle  of  incidence,  A  B  D,  is  precisely 
equal  to  the  angle  of  reflection,  E  B  D. 
If  the  light  falls  perpendicularly  upon  the 
surface,  F  C,  as  in  the  direction  D  B,  it 
will  be  reflected  in  the  same  line,  B  D ; 
or  in  other  words,  the  incident  and  re- 
flected ray  will  coincide. 

The  same  law  holds  good  in  regard  to 

every  form  of  surface,  curved  as  well  as  plane,  since  a  curve  may  bo  supposed 
to  be  formed  of  an  infinite  number  of  little  planes. 

QUESTIONS.— When  is  a  body  light-colored,  and  when  dark?  What  are  transparent 
and  opaque  bodies?  What  are  luminous  bodies?  How  are  bodies  not  luminous  ren- 
dered visible  ?  What  is  the  law  of  the  reflection  of  light  ? 


118  PRINCIPLES     OF     CHEMISTRY. 

195.  Refract  ion. —When  a  ray  of  light  falls  perpen- 
dicularly upon  the  surface  of  an  uncryst alii  zed  transparent 
substance  of  uniform  density,  it  continues  on  its  course 
unchanged  ;  but  if  it  falls  upon  the  surface  obliquely,  its 
direction  is  suddenly  changed  as  it  enters  the  transparent 
object,  or  medium  ;  it  then  passes  on  in  its  new  direction 
in  a  straight  line,  and  on  quitting  the  medium,  it  is  again 
abruptly  bent  back  to  its  original  course,  provided  the 
surface  of  entrance  and  the  surface  of  exit  be  parallel  to 
each  other.  Such  a  change  in  the  course  of  a  ray  of  light 
is  termed  Kefraction. 

When  the  ray  of  light  passes  from  a  rarer  to  a  denser  medium  (as  from  air 
into  glass  or  water),  the  ray  is  bent  or  refracted  toward  a  line  perpendicular 
to  that  point  of  the  surface  on  which  the  light  falls ;  when,  on  the  contrary, 
the  ray  passes  from  a  denser  to  a  rarer  medium,  the  ray  is  bent  in  the  opposite 
direction,  or  from  the  perpendicular. 

FIG.  51.  Thus,  in  Fig.  51,  suppose  n  m  to  represent  the 

surface  of  water,  and  S  0  a  ray  of  light  striking 
upon  its  surface.  When  the  ray  S  0  enters  the 
water,  it  will  no  longer  pursue  a  straight  course, 
but  will  be  refracted,  or  bent  toward  the  perpen- 
dicular line,  A  B,  in  the  direction  0  H.  The  denser 
the  water  or  other  fluid  may  be,  the  more  the  ray 
S  0  H  will  be  refracted,  or  turned  toward  A  B. 
If,  on  the  contrary,  a  ray  of  light,  H  0,  passes  from 
the  water  into  the  air,  its  direction  after  leaving  the  water  will  be  further 
from  the  perpendicular  A  B,  in  the  direction  0  S. 

A  straight  stick,  partly  immersed  in  water,  appears  to  be  broken  or  bent 
at  the  point  of  immersion.     This  is  owing  to  the  fact  that  the  rays  of  light 
proceeding  from  the  part  of  the  stick  contained  in  the  water  are  refracted,  or 
FIG.  52.          caused  to  deviate  from  a  straight  line  as  they  pass  from  tho 
water  into  the  air ;  consequently  that  portion  of  the  stick 
immersed  in  the  water  will  appear  to  be  lifted  up,  or  to 
be  bent  in  such  a  manner  as  to  form  an  angle  with  tho 
part  out  of  the  water. 

The  bent  appearance  of  the  stick  in  water  is  represented 
in  Fig.  52.  For  the  same  reason,  a  spoon  in  a  glass  of 
water,  or  an  oar  partially  immersed  in  water,  always  ap- 
pears bent 

QUESTIONS.— What  is  understood  by  the  refraction  of  light  ?  When  will  a  ray  of  light 
be  transmitted  through  a  transparent  substance  without  refraction  ?  In  what  manner  is 
a  ray  of  light  refracted  in  pausing  from  a  rarer  to  a  denser  medium,  and  in  the  reverse 
direction  ?  What  familiar  fact  illustrates  this  principle  ? 


PROPERTIES     OF     LIGHT.  119 

196.  Variations  of  Refractive  Power, — No  law  has  yet 
been  discovered  which  will  enable  us  to  judge  of  the  re- 
fractive power  of  bodies  from  their  other  qualities.     As  a 
general  rule,  dense  bodies  have  a  greater  refractive  power 
than  those  which  are  rare  ;  and  the  refractive  power  of  any 
particular  substance  is  increased  or  diminished  in  the  same 
ratio  as  its  density  is  increased  or  diminished. 

Refractive  power  seems  to  be  the  only  property,  except  weight,  which  is 
unaltered  by  chemical  combination  ;  so  that  by  knowing  the  refractive  power 
of  the  ingredients,  we  can  calculate  that  of  the  compound. 

All  highly  inflammable  bodies,  such  as  oils,  hydrogen,  the  diamond,  phos- 
phorus, sulphur,  amber,  camphor,  etc.,  have  a  refractive  power  from  ten  to 
seven  times  greater  than  thai  of  incombustible  substances  of  equal  density. 

Of  all  transparent  bodies  the  diamond  possesses  the  greatest  refractive  or 
light-bending  power,  although  it  is  exceeded  by  a  few  deeply-colored,  almost 
opaque  minerals.  It  is  in  part  from  this  property  that  the  diamond  owes  its 
brilliancy  as  a  jewel. 

Many  years  before  the  combustibility  of  the  diamond  was  proved  by  ex- 
periment, Sir  Isaac  Newton  predicted,  from  the  circumstance  of  its  high  re- 
fractive power,  that  it  would  ultimately  be  found  to  be  inflammable. 

The  determination  of  the  refracting  power  of  a  body  is  often  a  valuable 
guide  in  estimating  its  chemical  purity.  The  adulteration  of  essential  oils 
may  in  this  way  be  often  detected  with  ease,  when  it  would  be  otherwise 
difficult  to  ascertain  it.  Thus  genuine  oil  of  cloves  has  a  refractive  power 
expressed  by  the  numbers  1,535,  while  that  of  an  impure  and  adulterated 
specimen  was  not  more  than  ],498. 

197.  Double   Refraction  is   a  property   which   certain 
transparent  substances  possess,  of  causing  a  ray  of  light  in 
passing  through  them  to  undergo  two  refractions  ;  that 
is,  the  single  ray  of  light  is  divided  into  two  separate  rays. 

A  very  common  mineral  called   "Iceland  spar,"  -pI(J  53 

which  is  a  crystallized  form  of  carbonate  of  lime,  is 
a  remarkable  example  of  a  body  possessing  double 
refracting  properties.  It  is  usually  transparent  and 
colorless,  and  its  crystals,  as  shown  in  Fig.  53,  have 
the  geometrical  form  of  a  rhomb,  or  rhomboid  ; — this 
term  being  applied  to  a  solid  bounded  by  parallel 
faces,  inclined  to  each  other  at  an  angle  of  105°. 

QUESTIONS.— What  estimate  can  we  form  of  the  refractive  power  of  a  body  from  its  other 
qualities  ?  What  is  the  refractive  property  of  inflammable  substances  ?  What  transpa- 
rent substance  possesses  the  greatest  refractive  power  ?  How  may  refraction  be  used 
for  determining  the  chemical  purity  of  a  substance  ?  What  is  an  illustration  of  this  ? 
What  is  double  refraction  ?  What  substance  possesses  doubly  refracting  powers  in  a  re- 
markable degree  ? 


120 


PRINCIPLES     OF     CHEMISTRY. 


FIG.  54. 


The  manner  in  which  a  crystal  of  Iceland  spar  divides  a  ray  of  light  into 
two  separate  portions  is  clearly  shown  in  Fig.  54;  in 
which  S  T  represents  a  ray  of  light,  falling  upon  a  sur- 
face of  a  crystal  of  Iceland  spar,  A  D  E  C,  in  a  perpen- 
dicular direction.  Instead  of  passing  through  without  any 
refraction,  as  it  would  in  case  it  had  fallen  perpendicu- 
larly upon  the  surface  of  glass,  the  ray  is  divided  into 
two  separate  rays,  the  one,  T  0,  being  in  the  direction  of 
the  original  ray,  and  the  other,  T  E,  being  bent  or  re- 
fracted. The  first  of  these  rays,  or  the  one  which  follows 
the  ordinary  law  of  refraction,  is  called  the  "  ordinary" 
ray ;  the  second,  which  follows  a  different  law,  is  called 
the  "  extraordinary"  ray. 

If  we  look  at  an  object,  as  a  dot,  a  letter,  or  a  line,  through  a  plate  of  glass 
FIG.  55.  it  appears  single  ;  but  if  a  double  re- 

fracting substance,  as  a  plate  of  Ice- 
land spar,  be  substituted,  a  double 
image  will  be  perceived,  as  two  dots, 
two  letters,  two  lines,  etc.  This  re- 
sult of  double  refraction  is  represented 
in  Fig.  55. 

The  phenomenon  of  double  refrac- 
tion is  due  entirely  to  the  peculiar 
molecular  structure  of  the  medium  through  which  the  light  passes.  This  is 
proved  by  taking  a  cube  of  regularly  annealed  glass,  which  produces  but  one 
refracted  ray,  and  heating  it  unequally,  or  subjecting  it  to  pressure :  a  change 
is  thereby  effected  in  the  arrangement  of  its  parts,  and  double  refraction  takes 
place. 

The  diamond  may  be  distinguished  from  all  other  precious  stones,  with  a 
single  exception  (the  garnet),  by  having  only  a  single  refraction,  the  others 
possessing  double  refraction,  or  giving  a  double  image  of  a  taper  or  small 
light  viewed  through  their  faces.  By  the  same  means  all  precious  stones,  ex- 
cept diamond  and  garnet,  may  be  distinguished  from  artificial  ones,  by  the 
former  having  double  refraction,  and  the  latter  only  single  refraction. 

198.  Polarization,— Light  which  has  been  refracted  from 
certain  surfaces,  or  transmitted  through  certain  substances, 
under  certain  special  conditions,  assumes  new  properties, 
and  is  no  longer  reflected,  refracted,  or  transmitted  as 
before.  This  change  in  the  action  of  light  is  called  Po- 
larization, and  a  ray  thus  modified  is  said  to  be  polarized. 

A  ray  of  light  which  by  any  method  has  become  polarized,  seems  to  have 

QUESTIONS. — To  what  is  this  phenomenon  due  ?  How  may  th^  diamond  be  distinguished 
from  all  other  precious  stones?  What  is  polarized  light?  What  is  the  origin  and  ex- 
planation of  this  term  ? 


PROPERTIES   OF   LIGHT.  121 

acquired  a  property  of  possessing  sides.  If  the  original  ray  be  supposed  to  be 
a  cylindrical  rod,  polished  or  white  all  round,  which  is  capable  of  being  re- 
flected from  a  polished  surface  whatever  part  of  its  circumference  may  strike 
that  surface,  the  polarized  ray  may  be  compared  to  a  square-shaped  rod  with 
four  flat  sides,  two  of  which  (opposite),  bright  and  polished,  are  capable  of  re- 
flection, while  two,  black  or  dull,  are  not.  Now,  the  word  "  poles,''  in  physi- 
cal science,  is  often,  used  to  denote  the  ends  or  sides  of  any  body  which  have 
acquired  contrary  properties,  as  the  opposite  ends  of  a  magnet,  which  are 
called  the  positive  and  negative  poles.  By  analogy,  the  ray  of  light  whose 
sides  lying  at  the  right  angles  with  each  other,  were  found  to  be  endowed 
with  opposite  physical  properties,  was  said  to  be  polarized.  The  term  is  un- 
fortunate, but  is  too  firmly  engrafted  upon  science  to  be  changed. 

The  explanation  of  change  occasioned  by  the  polarization  of  light  may  be 
briefly  stated  as  follows : — According  to  the  undulatory  theory,  common  light 
is  assumed  to  be  produced  by  vibrations  of  the  ethereal  particles  in  two  planes 
at  right  angles  to  the  pi  ogress  of  the  wave;  there  are  perpendicular  vibra- 
tions, and  there  are  horizontal  vibrations.  Polarized  light,  on  the  contrary, 
is  light  occasioned  by  vibrations  taking  place  in  only  one  plane — the  effect  of 
whatever  produces  polarization  being  to  suppress  all  the  vibrations  which 
take  place  in  one  plane  at  right  angles  to  the  other.  Hence  the  different 
properties  possessed  by  opposite  sides  or  poles  of  the  ray. 

Common  light  is  converted  into  polarized  light,  for  all  practical  purposes 
and  for  experiment,  in  three  ways — 

First, — When  it  is  reflected  from  glass  at  an  angle  of  incidence  of  fifty-six 
degrees,  forty-five  minutes  from  the  perpendicular.  It  is  also  polarized  by 
reflection  from  almost  any  bright  non-metallic  surface,  but  the  maximum  po- 
larizing angle  for  each  different  surface  is  peculiar  to  itself.  When  the  re- 
flection from  glass  takes  place  at  the  exact  angle  of  56°  45',  all  the  light  is 
polarized,  but  when  the  angle  of  reflection  deviates  from  this  amount,  some 
of  the  reflected  light  will  remain  unchanged,  the  quantity  uupolarized  being 
in  proportion  to  the  deviation. 

Secondly, — Light  may  be  polarized  by  transmission  through  a  bundle  con- 
sisting of  from  sixteen  to  eighteen  plates  of  thin  glass  or  mica. 

Thirdly, — Light  is  polarized  by  passing  through  certain  transparent  crys- 
tals, especially  those  which  possess  the  property  of  double  refraction. 

199.  Peculiarities  of  Polarized  Light ,— If  a  ray  of  light 
which  has  been  polarized  by  reflection  from  a  glass  plate  is  caused  to  fall 
upon  a  second  plate,  it  is  not  reflected  as  common  light  would  be.  If  the 
plane  of  the  second  reflecting  surface  is  so  inclined  to  the  first,  that  the 
ray  falls  at  an  angle  of  56°,  the  ray  is  not  reflected  at  all,  but  vanishes;  if, 
on  the  contrary,  the  plane  of  the  second  reflecting  surface  is  parallel  to  the 
first,  it  is  entirely  reflected.  It  is  also  a  peculiar  property  of  polarized  light, 


QUESTIONS. — In  -what  three  ways  may  light  be  polarized  ?  What  peculiarities  are  mani- 
fested by  light  polarized  by  reflection  from  glass  ?  How  is  polarized  light  affected  by 
certain  transparent  substances  ? 

6 


122  PRINCIPLES     OF     CHEMISTRY. 

that  it  will  not  pass  through  certain  substances  which  aro  transparent  to  com- 
mon light.  This  is  shown  in  a  remarkable  manner  by  a  mineral  substance 
called  tourmaline,  the  internal  structure  of  which  is  such,  that  a  ray  of  com- 
mon light  which  has  passed  through  a  thin  plate  of  it,  and  thereby  become 
polarized,  can  not  pass  through  a  second  similar  plate,  if  it  is  placed  at  right 
angles  to  the  first. 

For  example,  in  Fig.  56,  if  a  ray  of  light  be  caused  to  pass  through  a  thin 
p       g£  plate  of  tourmaline,  as  c  d,  in  the  direction 

of  the  line  a  &,  and  be  received  upon  a  sec- 
ond plate,  e  /,  placed  symmetrically  with  the 
first,  it  passes  through  both  without  diffi- 
culty :  but  if  the  second  plate  bo  turned  a 
quarter  round,  as  in  the  direction  g  h,  the 
light  is  totally  cut  off. 

200.  Discovery    of    Polarized    Light , — The  phenomenon   of 
polarized  light  was  discovered  in  1808,  by  Malus,  a  young  engineer  officer  of 
Paris.     On  one  occasion,  as  he  was  viewing  through  a  double  refracting  prism 
of  Iceland  spar  the  light  of  the  sun  reflected  from  a  glass  window  in  one  of 
the  French  palaces,  he  observed  some  very  peculiar  effects.     The  window  ac- 
cidentally stood  open  like  a  door  on  its  hinges,  at  an  angle  of  56°  and  Malus 
noticed  that  the  light  reflected  at  this  angle  was  endowed  with  properties 
which  distinguish  it  from  ordinary  light. 

201.  Practical   Applications  of  Polarized    Light , — Tho 
principles  of  polarized  light  have  been  applied  to  the  determination  of  muny 
practical  results.     Thus,  it  has  been  found  that  all  reflected  light,  come  from 
whence  it  may,  acquires  certain  properties  which  enable  us  to  distinguish  it 
from  direct  light ;  and  the  astronomer,  in  this  way,  is  enabled  to  determine 
with  infallible  precision  whether  the  light  he  is  gazing  on  (and  which  may 
have  required  hundreds  of  j^ears  to  pass  from   its  source  to  the  eye),  is  inhe- 
rent in  the  luminous  body  itself,  or  is  derived  from  some  other  source  by  re- 
flection. 

It  has  been  also  ascertained  by  Arago  that  light  proceeding  from  incandes- 
cent bodies,  as  red  hot  iron,  glass,  and  liquids,  under  a  certain  angle,  is  po- 
larized light ;  but  that  light  proceeding,  under  the  same  circumstances,  from 
an  inflamed  gaseous  substance,  such  as  is  used  in  street  illumination,  is  always 
in  a  natural  state,  or  unpolarized.  Applying  these  principles  to  the  sun,  ho 
discovered  that  the  light-giving  substance  of  this  luminary  was  of  the  nature 
of  a  gas,  and  not  a  red  hot  solid  or  liquid  body. 

"When  we  transmit  light,  whether  common  or  polarized,  through  a  piece  of 
well  annealed  glass,  it  suffers  no  change,  and  we  see  no  structure  in  the  glass 
different  from  what  we  would  see  if  we  looked  through  pure  water.  But  if 

QUESTIONS.—  Illustrate  this  in  the  case  of  tourmaline.  When  and  how  was  polarized 
light  discovered  ?  What  are  some  of  the  practical  applications  of  polarized  light  ?  What 
is  the  difference  between  light  emitted  from  incandescent  solids  and  inflamed  gases? 
"What  inference  has  Arago  made  respecting  the  constitution  of  the  sun  ?  What  informa- 
tion does  polarized  light  impart  respecting  the  structure  of  bodies  ? 


PROPERTIES     OF   LIGHT.  123 

we  make  heat  pass  through  the  glass,  by  placing  the  edge  of  the  plate  upon 
a  heated  iron,  or  if  we  either  bend  or  compress  the  glass  by  mechanical  force, 
its  structure,  or  the  mechanical  condition  of  its  particles,  will  bo  changed.  If 
we  now  transmit  common  light  through  the  glass  thus  changed,  the  change 
will  not  be  visible ;  but  if  we  transmit  polarized  light  through  it,  and  allow 
that  light  to  be  reflected  from  a  transparent  body  at  an  angle  of  about  66°, 
and  in  a  plane  at  right  angles  to  that  in  which  the  common  light  was  reflected 
and  polarized,  the  observer,  looking  through  the  glass,  will  see  the  most  bril- 
liant colors,  indicating  the  effects  of  the  compressing  or  dilating  forces,  or  of 
the  contracting  or  expanding  cause — the  degree  of  compression  or  dilatation, 
of  expansion  or  contraction,  being  indicated  by  the  colors  displayed  at  par- 
ticular parts  of  the  glass.  In  this  way  polarized  light  enables  us  to  discover 
that  certain  portions  of  a  body  have  been  subjected  to  certain  mechanical  forces, 
the  nature  of  which  must  be  sought  for  in  the  circumstances  under  which  the 
body  has  been  originally  formed,  or  in  which  it  has  been  subsequently  placed. 
On  this  principle,  many  bodies  which  are  quite  transparent  to  the  eye,  and 
which  upon  examination  appear  to  be  perfectly  uniform,  or  homogenous  in 
structure,  exhibit,  under  polarized  light,  the  most  exquisite  organization.* 


*  "  Integumentary  substances  in  particular  form  a  brilliant  and  interesting  class  of  ob- 
jects. A  section  of  a  horse1  s  hoof  has  the  effect  of  the  richest  Brussels'  carpet,  with  a 
symmetrical  pattern  that  might  bo  copied  by  the  loom. 

"  The  vegetable  world  has  a  less  brilliant  display  to  make,  but  is  still  replete  with  in- 
terest. Cuticles  containing  flint  are  often  very  beautiful ;  that  of  the  common  fiaarestail 
presents  a  remarkably  neat  shawl  pattern  in  stripes.  Very  curious  optical  effects  are  pre- 
sented by  the  various  starches.  The  starch  called  tous-les-mois,  having  the  largest  grains, 
is  usually  selected  for  exhibition. 

"  Crystalline  forms,  however,  afford  the  most  striking  exhibitions  of  the  phenomena 
of  polarized  light.  Salacine,  a  salt  extracted  from  the  bark  of  the  willow,  offers,  when 
almost  an  imperceptible  film,  the  appearance  of  a  pavement  consisting  not  merely  of  gold, 
but  of  lapis  lazuli,  ruby,  emerald,  and  opal.  Chlorate  of  potash  strews  the  field  of  view 
with  liberal  handfuls  of  pyramidal  jewels.  Chromate  of  potash,  which  forms  a  bright 
yellow  solution,  presents  a  remarkable  assemblage  of  club-shaped  crystals,  which  have 
been  compared  to  vast  heaps  of  constables'  staves.  Oxalate  of  potash,  like  several  other 
combinations  of  oxalic  acid,  is  a  salt  of  such  variety  and  brilliancy,  that  its  crystals,  float- 
ing and  glowing  in  a  few  drops  of  solution  on  the  slide,  look  as  if  their  form  and  color 
were  the  result  of  a  Chinese  imagination  in  its  happiest  moments. 

"  Fancy  yourself  living  in  a  region  solely  illuminated  by  Aurora  boreales — imagine  a 
country  where  every  passing  cloud  throws  a  diverse-colored  shadow  of  gorgeous  hues 
across  your  path  ;  where  the  air  breeds  rainbows  without  the  aid  of  a  shower,  and  where 
the  summer  breeze  breaks  those  rainbows  into  irregular  lengths,  fragments,  and  glitter- 
ing dust,  scattering  them  broadcast  over  the  land,  like  autumnal  leaves  swept  by  a  galo 
from  the  forest,  and  you  have  an  approximate,  and  by  no  means  exaggerated  idea  of  the 
effects  of  polarized  light  on  substances  capable  of  being  affected  by  it.  For,  it  is  light  en- 
dowed with  extra  delicacy,  subtlety,  and  versatility.  It  renders  visible  minute  details  of 
structure  in  the  most  glaring  colors  ;  it  gauges  crystalline  films  of  infinitesimal  thinness  ; 
it  betrays  to  the  student's  search,  otherwise  inappreciable  differences  of  density  or  elas- 
ticity in  the  various  parts  of  tissues.  Indeed,  as  a  detector,  polarized  light  is  invaluable, 
acting  the  part  of  a  spy  under  the  most  unexpected  circumstances.  It  denounces  as  cot- 
ton what  you  believed  to  be  silk ;  it  demonstrates  disease  where  you  supposed  health. 
It  adorns  objects  that  are  vile  and  mean,  whose  destiny  is  only  to  be  cast  out—such  aa 
parings  of  nails,  shavings  of  animals'  hoofs,  cuticle  rubbed  or  peeled  from  the  stems  of 


124  PEINCIPLES     OF     CHEMISTRY. 

In  a  similar  manner  the  chemist  is  able  to  determine,  by  the  manner  in 
which  light  is  reflected  or  polarized  by  a  crystallized  body,  whether  it  has 
been  adulterated  by  the  addition  of  foreign  substances.  Polarized  light,  also, 
in  certain  cases,  affords  the  best  means  of  arriving  at  a  knowledge  of  the  va- 
rieties and  proportion  of  sugar  in  the  juices  of  plants,  and  in  complex  sac- 
charine liquids. 

202.  Magnetization   of   Ligh  t. — Recent  experiments  made   by 
Professor  Faraday  have  proved  that  magnetism  has  the  power  of  influencing 
a  ray  of  light  in  its  passage  through  transparent  bodies.     This   fact  is  shown 
by  the  following  experiment : — A  ray  of  polarized  light  is  passed  through  a 
piece  of  glass,  or  a  crystal,  or  along  the  length  of  a  tube  filled  with  some  trans- 
parent fluid,  and  the  line  of  its  path  carefully  observed ;  if,  when  this  is  done, 
the  solid  or  fluid  body  is  brought  under  powerful  magnetic  influence,  such  as 
may  be  called  into  action  by  the  circulation  of  an  electric  current  around  a 
bar  of  soft  iron,  it  will  be  found  that  the  polarized  light  is  disturbed,  and  that 
it  does  not  continue  to  pass  through  the  medium  along  the  same  line.     "  As 
this  effect  is  most  strikingly  shown  in  bodies  of  the  greatest  density  and  di- 
minishes in  fluids,  the  particles  of  which  are  easily  movable  upon  each  other, 
and  has  not  as  yet  been  observed  in  any  gaseous  medium,  the  question  hag 
arisen,  does  magnetism  act  directly  upon  the  ray  of  light,  or  only  indirectly, 
by  producing  a  molecular  change  in  the  body  through  which  the  ray  is  pass- 
ing?    In  the  present  state  of  science  no  satisfactory  reply  can  be  given."— 
ROBERT  HUNT. 

203.  Decomposition    of  Light . — When  a  beam  of  light,  S  A, 
Fig.  57,  from  the  sun  is  admitted  into  a  dark  room,  by  a  small  aperture  in  the 
window-shutter,  and  is  intercepted  in  its  passage  by  a  wedge,  or  solid  angle 
of  glass  called  a  prism,  it  is  refracted,  or  bent  from  its  course  as  it  enters, 
and  again  as  it  issues  from  the  glass.     In  place  of  forming  a  circular  spot  of 
white  light  on  the  floor  of  the  apartment,  as  it  would  have  done  if  allowed  to 
proceed  in  its  original  direction,  S  K.  it  illuminates  with  several  colors  an 
oblong  space,  H,  on  the  opposite  wall,  or  on  a  white  screen  properly  placed 
to  receive  it.     This  oblong  colored  image  is   called  the  prismatic,  or  solar 
spectrum. 

Newton,  who  first  carefully  investigated  this  remarkable  fact,  distinguished 
seven  different  colors,  which  gradually  shade  off  one  into  the  other  in  the 
following  order,  commencing  at  the  upper  part  of  the  spectrum,  viz.,  violet, 
indigo,  blue,  green,  yellow,  orange,  and  red. 

White  light  may,  therefore,  be  regarded  as  the  result 


plants,  offscouring  of  our  kitchens  and  store-rooms,  sugar,  acids,  and  salts — with  the  most 
magnificent,  the  most  resplendent  tints,  such  as  are  seen  when  the  sun  streams  through 
the  stained  glass  windows  of  a  Norman  cathedral." 

QUESTIONS. — Can  polarized  light  be  made  available  in  determining  the  chemical  char- 
acter of  a  substance  ?  What  influence  has  magnetism  on  light  ?  What  is  meant  by  the 
decomposition  of  light  ?  What  is  the  solar  spectrum  ?  How  are  the  colors  of  the  spec- 
trum arranged  ?  How  may  white  light  be  regarded  ? 


PROPERTIES    OF   LIGHT. 


125 


of  a  mixture  of  rays  of  different  colors,  which  are  unequally 
acted  upon  by  the  prism — each  color  possessing  its  own 
peculiar  refrangibility. 

Thus  the  red  rays,  which  are  the  least  refracted,  or  the  least  turned  from 
their  course  by  the  prism,  always  occur  at  the  bottom  of  the  spectrum,  while 
the  violet,  which  is  the  most  refracted,  occurs  at  the  top ;  the  remaining  colors 
being  arranged  in  the  intermediate  space  in  the  order  of  their  refrangibility. 

FIG.  57. 


The  seven  different  rays  of  light,  when  once  separated  and  refracted  by  a 
prism,  are  not  capable  of  being  separated  and  refracted  again ;  but  if  by  means 
of  a  convex  lens  they  are  collected  together  and  converged  to  a  focus,  they 
will  form  white  light. 

204.  Lines  in  the  Solar  Spectrum , — When  the  solar  spec- 
trum is  formed  in  the  usual  manner  upon  a  white  screen,  it  appears  like  a 
continuous  band  of  colored  light.  By  taking  certain  precautions,  however,  it 
may  be  seen  that  this  luminous  band  is  traversed  in  the  direction  of  its 
breadth  by  numerous  dark  lines,  varying  in  different  parts  in  width  and  dis- 
tinctness ;  or,  in  other  words,  there  are  interruptions  in  the  spectrum  where 
there  is  no  light  of  any  color.  These  lines  are  independent  of  the  refracting 
medium,  and  always  occur  in  the  same  color  and  at  corresponding  points  of 
the  spectrum. 

The  position  of  these  dark  spaces  varies,  however,  with  the  source  of  light. 
"With  a  few  exceptions,  each  of  the  fixed  stars  has  a  system  of  lines  peculiar 
to  it.  The  light  proceeding  from  the  fixed  stars  Sirius  and  Castor  agree  very 
nearly  in  this  respect,  but  differ  from  the  light  of  the  sun.  The  spectrum, 
however,  which  is  formed  from  the  light  proceeding  from  the  fixed  star  Pol- 

QUESTIOKS — Are  the  colored  rays  capable  of  further  decomposition  by  refraction? 
What  effect  results  from  their  union?  What  lines  are  seen  in  the  spectrum?  What  dif- 
ferences have  been  obserred  in  light  emanating  from  different  sources? 


126  PRINCIPLES     OF     CHEMISTRY. 

lux  is  the  same  as  that  of  the  sun.     Every  artificial  light,  also,  shows  some 
peculiarity  in  this  respect. 

Eecent  discoveries  have  given  to  these  phenomena  an  entirely  chemical 
character.  It  has  been  found  that  the  white  light  of  ordinary  flames  requires 
merely  to  be  sent  through  a  certain  gaseous  medium  (such  as  nitrous  acid 
vapor)  to  acquire  more  than  a  thousand  dark  lines  in  its  spectrum  ;  and  it 
has  hence  been  inferred,  that  it  is  the  presence  of  certain  gases  in  the  at- 
mosphere of  the  sun  and  of  the  fixed  stars,  which  occasion  the  observed  de- 
ficiencies in  the  spectra  formed  from  their  light.  In  this  way  points  of  re- 
semblance and  difference  may  be  traced  between  the  constitution  of  our  sun 
and  the  suns  of  other  systems. 

In  Fig.  58,  No.  1  shows  the  principal  dark  lines  of  the  pure  solar  spectrum ; 
No.  2,  the  alteration  occasioned  by  passing  solar  light  through  the  vapor  of 
bromine ;  while  No.  3  represents  the  very  different  result  effected  by  the 
peroxyd  of  nitrogen. 

FiG.  58. 


205.  Calorific  and  Chemical  Elements  of  Solar  Light. — 
Solar  light,  in  addition  to  the  luminous  principle  which 
produces  the  phenomena  of  color  and  is  the  cause  of 
vision,  contains  two  other  principles,  viz.,  heat  and  actin- 
ism, or  the  chemical  principle.  These  principles  are  in- 
visible to  the  eye,  and  have  only  been  discovered  by  their 
effects  on  other  bodies. 

The  constitution  of  the  solar  ray  may  be  compared  to  a  bundle  of  three 
sticks,  one  of  which  represents  heat,  another  light,  and  a  third  the  actinic 
principle. 

We  know  that  these  three  principles  exist  in  every  ray  of  solar  light,  be- 
cause we  are  able  to  separate  them  in  a  great  degree  from  each  other.  Thus, 
when  we  decompose  a  ray  of  solar  light  by  means  of  a  prism,  and  throw  the 
spectrum  upon  a  screen,  the  luminous,  the  calorific,  and  the  chemical  or  ac- 
tinic radiations,  will  each  be  refracted,  or  bent  out  of  their  course  in  different 

QUESTIONS.— What  discoveries  have  given  to  these  lines  a  chemical  character?  What 
three  principles  are  included  in  solar  light  ?  How  do  we  know  of  the  existence  of  these 
principles  ?  How  are  they  affected  by  the  prism  ? 


PROPERTIES     OF     LIGHT.  127 

degrees,  and  will  consequently  assume  different  positions  upon  the  screen. 
In  other  words,  the  light  of  the  sun  refracted  by  the  prism  produces  in  reality 
three  spectra,  one  visible  and  two  invisible. 

The  calorific,  or  heat  radiations,  will  be  refracted  least,  and  their  maximum 
point  will  be  found  but  slightly  thrown  out  of  the  right  line  which  the  solar 
ray  would  have  traversed  had  it  not  been  intercepted  by  the  prism.  Tho 
heat  diminishes  with  much  regularity  on  each  side  of  this  line. 

The  luminous  radiations  are  subject  to  a  greater  degree  of  refraction ;  their 
point  of  maximum  intensity  being  in  the  yellow  ray,  lying  considerably  above 
the  point  of  greatest  heat  The  light  diminishes  oil  each  side  of  it,  producing 
orange,  red,  and  crimson  colors  below  the  maximum  point,  and  green,  blue, 
and  violet  above  it 

The  radiations  which  produce  chemical  action  are  more  refrangible  than 
either  the  calorific  or  luminous  radiations,  and  the  maximum  of  chemical 
power  is  found  at  that  point  of  the  spectrum,  where  light  is  feeble,  and  whero 
scarcely  any  heat  can  be  detected. 

The  positions  in  the  spectrum  of  the  heat  and  actinic  radiations,  which  aro 
invisible  to  the  eye,  may  be  found  by  experiment.  Thus,  if  we  place  a  deli- 
cate thermometer  in  the  different  rays  of  the  spectrum  (§  203,  Fig,  57),  it 
will  be  found  that  the  indigo  and  violet  rays  scarcely  affect  it  at  all,  while 
the  yellow  ray,  which  is  the  most  luminous,  is  inferior  in  heating  action  to 
the  red  ray,  which,  yielding  but  little  light,  possesses  the  greatest  amount 
of  heat  If  now  the  thermometer  be  carried  a  little  below  and  just  out  of 
the  red  ray,  into  the  darkened  space,  it  will  exhibit  the  greatest  increase  in 
temperature,  thus  proving  the  presence  of  a  heating  ray  in  solar  light  inde- 
pendent of  the  luminous  ray.  In  a  like  manner,  by  substituting  a  chemically 
prepared  surface,  as  a  piece  of  photographic  paper,  for  the  thermometer,  the 
presence  of  a  chemical  ray  can  be  proved  in  the  darkened  space  at  the  other 
end  of  the  spectrum,  and  near  to  the  blue  and  violet  rays. 

200.  Analysis  of  Heat . — The  heat  emanating  from  the  sun  or  from 
a  bright  flame,  consists  of  rays  which  differ  from  each  other  as  much  as  the 
red,  yellow,  and  blue  rays  do  which  constitute  white  light.  Heat  radiated 
from  a  body  having  a  lower  temperature  than  800°  P.,  is  much  less  refrang- 
ible than  red  light  -  but  if  the  temperature  of  the  radiating  body  be  increased, 
it  emits,  in  addition  to  the  rays  previously  emitted,  others  of  a  higher  refrang- 
ibility,  until  at  last  some  few  of  its  rays  become  as  refrangible  as  the  least 
refrangible  rays  of  light  The  body  then  appears  of  the  same  color  as  the 
least  refrangible  rays  of  light,  and  is  said  to  be  red  hot.  If  it  be  heated  more, 
it  emits,  in  addition  to  the  red,  still  more  refrangible  rays,  viz.,  orange ;  then 
(at  a  higher  temperature)  yellow  rays  aro  added,  and  so  on,  until  when  tha 
body  is  white  hot,  it  emits  all  the  colors  visible  to  us ;  and  in  some  instances 
(of  very  intense  heat),  even  the  invisible  chemical  rays,  more  refrangible  than 
the  violet,  are  emitted,  though  in  less  quantity  than  in  the  solar  rays. 

QtresTiosrs.— Is  heat  emanating  from  various  sources  uniform  in  character  ?  Hov  do 
the  rays  of  heat  differ  in  refrangibility  ? 


128  PRINCIPLES     OF     CHEMISTRY. 

Thus  light,  in  one  sense,  appears  to  be  nothing  more  than  visible  heat, 
and  heat  invisible  light — the  constitution  of  the  eye  being  such  that  it  can 
perceive  one  and  not  the  other,  hi  the  same  way  as  the  ear  can  appreciate 
vibrations  of  sound  more  rapid  than  sixteen  per  second,  but  not  those  which 
are  less  rapid. 

A  series  of  interesting  experiments  made  some  years  since  by  Melloni, 
show  very  conclusively  that  heat  emanating  from  different  sources  differs  in 
its  nature,  in  the  same  manner  as  the  light  of  a  red  body  differs  from  that 
of  a  blue.  He  employed  four  sources  of  caloric,  two  of  which  were  lumin- 
ous and  two  non -luminous,  or  obscure ;  namely,,  an  oil-lamp  without  a  glass, 
incandescent  platinum,  copper  heated  to  696°  F,,  and  a  copper  vessel  filled 
with  water  at  a  temperature  of  178°  F.  Rock-salt  transmitted  heat  in  the 
proportion  of  92  rays  out  of  every  100  from  each  of  these  sources ;  but  every 
other  substance  pervious  to  ?adiant  heat,  whether  solid  or  liquid,  transmitted 
more  caloric  from  sources  of  high  temperature  than  from  such  as  were  low. 
For  instance,  a  clear  and  limpid  mineral,  the  fluate  of  lime,  transmitted  in 
the  proportion  of  78  rays  out  of  100  from  the  lamp,  69  from  the  platinum, 
42  from  the  copper,  and  33  from  the  hot  water-  while  transparent  rock  crys- 
tal transmitted  38  rays  in  100  from  the  lamp,  28  from  the  platinum,  6  from 
the  copper,  and  9  from  the  hot  water.  Pure  ice  transmitted  only  in  the 
proportion  of  6  rays  in  the  100  from  the  lamp,  and  entirely  excluded  those 
from  other  sources. 

The  discovery  of  the  fact  that  heat  proceeding  from  the  sun  or  any  other 
luminous  body  is  susceptible  of  division  into  rays,  differing  in  nature  and  in 
refrangibility,  has  furnished  an  explanation  of  many  curious  phenomena. 
Heat  from  very  intense  sources  is  more  refrangible  and  passes  more  readily 
through  most  substances  than  heat  of  low  intensity.  Thus,  the  heat  of  the 
sun  passes  readily  through  glass,  but  the  heat  of  a  fire  is  almost  entirely 
obstructed.  Advantage  has  been  taken  of  this  fact  by  those  who  have  oc- 
casion to  inspect  the  progress  of  operations  carried  on  in  furnaces  j  since  they 
are  able,  by  the  use  of  a  glass  screen,  to  protect  the  face  from  the  scorching 
rays  which  the  glass  absorbs,  although  it  offers  no  impediment  to  the  trans- 
mission of  light. 

It  is  a  well-known  fact  that  snow  which  lies  near  the  trunks  of  trees  or 
other  like  substances,  is  melted  much  more  rapidly  than  that  exposed  to  the 
action  of  the  direct  rays  of  the  sun.  The  reason  of  this  is,  that  the  heat  of 
the  sun,  being  heat  of  high  intensity  and  high  refrangibility,  passes  through 
the  snow  without  experiencing  a  great  degree  of  absorption  -  but  solar  heat, 
which  first  falls  upon  the  tree  and  is  then  radiated  upon  the  snow,  is  thereby 
changed  into  heat  of  low  refrangibility,  and  is  readily  absorbed  instead  of 
being  transmitted. 

207    Action    of  the    Chemical    Rays . — The  chemical  principle 

QTTESTIOWS. — Describe  the  experiments  of  Melloni.  What  results  have  followed  the  dis- 
covery of  the  analysis  of  heat  7  Why  win  glass  transmit  heat  from  the  sun,  and  not  from 
a  fire  ?  How  does  the  action  of  light  on  snow  vary  ?  What  is  the  character  of  the  chem- 
ical principle  of  light  ? 


PROPERTIES    OF    LIGHT,  129 

of  light  is,  without  doubt,  like  the  calorific  principle,  composed  of  rays  of  dif- 
ferent character,  and  of  different  refrangibihty.  Recent  experiments  of  Pro- 
fessor Stokes  of  England,  seem  to  show  that  when  the  invisible  rays  which 
occupy  in  the  spectrum  a  position  beyond  the  violet,  are  caused  to  pass 
through  a  solution  of  quinine,  they  are  changed  in  refrangibility,  and  become 
visible — appearing  as  a  sky-blue  light  at  a  point  far  beyond  the  usual  lu- 
minous limit  of  the  spectrum,  This  phenomenon  has  been  termed  the 
"  degradation  of  light." 

The  study  of  the  chemical  principle  contained  in  the  rays  of  solar  light  has 
rendered  probable  the  curious  fact,  that  no  substance  can  be  exposed  to  the 
Bun's  rays  without  undergoing  a  chemical  change ;  and  from  numerous  ex- 
amples it  would  seem  that  the  changes  in  the  molecular  condition  of  bodies 
which  sunlight  effects  during  the  daytime,  is  made  up  during  the  hours  of 
night,  when  the  action  is  no  longer  influencing  them.  Thus  darkness  ap- 
pears to  be  essential  to  the  healthy  condition  of  all  organized  and  unorgan- 
ized forms  of  matter. 

The  process  of  forming  Daguerreotype  and  other  photo- 
graphic pictures,  depends  solely  upon  the  actinic,  or 
chemical  influence  of  the  solar  ray. 

The  term  "photography,"  signifying  light  drawing,  which  is  the  general 
name  given  to  this  art,  is  unfortunate  and  ill-chosen,  for  not  only  does  light 
not  exercise  any  influence  in  producing  the  pictures,  but  it  tends  to  destroy 
them, 

That  the  luminous  principle  is  not  necessary  for  the  success  of  the  photo- 
graphic process,  may  be  proved  by  the  experiment  of  taking  a  daguerreotype 
in  absolute  darkness.  This  can  be  accomplished  in  the  following  manner : — • 
A  large  prismatic  spectrum  is  thrown  upon  a  lens  fitted  into  one  side  of  a 
dark  chamber  j  and  as  the  actinic  power  resides  in  great  activity  at  a  point 
beyond  the  violet  ray,  where  there  is  no  light,  the  only  rays  allowed  to  pass 
the  lens  into  the  chamber  are  those  beyond  the  limit  of  coloration,  and  non- 
luminous  ;  these  are  directed  upon  any  object,  and  from  that  object  radiated 
upon  a  highly  sensitive  photographic  surface.  In  this  way  a  picture  may  be 
formed  by  radiations  which  produce  no  effect  upon  the  eye. 

It  has  also  been  found  that  the  yellow,  the  orange,  and  the  red  rays  of 
light  possess  the  power  of  retarding  by  their  presence  all  chemical  or  pho- 
togenic action,  in  proportion  to  their  predominance ;  and  if  unaccompanied  by 
other  light,  they  arrest  the  effects  of  the  chemical  rays  altogether.  On  the 
contrary,  the  violet,  indigo,  and  blue  rays  of  light  favor  chemical  action.  This 
is  clearly  exemplified  in  the  following  manner :— If  an  engraving'  be  covered 
one  half  with  a  yellow  glass,  and  placed  in  front  of  a  camera  for  the  pur- 

QUESTIONS.— What  experiments  have  been  made  by  Mr.  Stokes  ?  What  curious  fact  has 
the  study  of  the  chemical  principle  of  light  evolved  ?  Upon  what  does  the  production  of 
photographic  pictures  depend  ?  What  experiment  shotf  s  that  light  is  not  necessary  for  the 
production  of  a  photographic  picture  ?  How  do  the  different  luminous  rays  of  the  solar 
beam  affect  the  chemical  principle  ?  What  experiments  and  facts  illustrate  their  rela- 
tive action  ? 

6* 


130  PRINCIPLES     OF     CHEMISTRY, 

pose  of  representation  on  a  daguerreotype  plate,  an  accurate  copy  will  be 
shortly  obtained  of  the  uncovered  portion,  while  the  yellow  screen  entirely 
prevents  the  plate  from  receiving  an  impression  of  the  rest.  But  if  the  en* 
graving  be  covered,  one  half  with  blue  and  the  other  half  with  yellow  glass, 
while  it  will  be  distinctly  discernible  to  the  eye  through  the  latter  and  not 
at  all  through  the  former,  the  camera  will  faithfully  copy  the  portion  which 
is  invisible,  but  wholly  neglect  the  other.  Again,  in  a  room  illuminated  solely 
through  red,  or  orange  glass,  in  which  light  may  fall  with  dazzling  luster,  no 
photographic  operations  can  be  conducted ;  while  if  blue  glass  be  substi- 
tuted, the  change,  while  it  will  dim  the  effulgence,  will  enable  the  photo- 
grapher to  exercise  his  art  with  success.  In  the  same  way,  during  certain 
states  of  the  atmosphere,  there  may  be  an  abundance  of  illuminating,  but 
very  few  photogenic  rays. 

208.  Influence  of  Light  on  Vegetation  .—There  are  many 
reasons  for  supposing  that  each  of  the  three  principles,  light,  heat,  and  actin- 
ism, included  in  the  solar  ray,  exercise  a  distinct  and  peculiar  influence  upon 
vegetation.  Thus  the  luminous  principle  controls  the  growth  and  coloration 
of  plants,  the  calorific  principle  their  ripening  and  fructification,  and  the  chem* 
ical  principle  the  germination  of  seeds.  Seeds  which  ordinarily  require  ten 
or  twelve  days  for  germination,  will  germinate  under  a  blue  glass  in  two  or 
three.  The  reason  of  this  is,  that  the  blue  glass  permits  the  chemical  prin- 
ciple of  light  to  pass  freely,  but  excludes,  in  a  great  measure,  the  heat  and 
the  light.  On  the  contrary,  it  is  nearly  impossible  to  make  seeds  germinate 
under  a  yellow  glass,  because  it  excludes  nearly  all  the  chemical  influence 
of  the  solar  ray» 

Further  consideration  of  the  chemical  effects  of  light  will  be  postponed 
Until  after  the  chemical  properties  of  the  elementary  bodies  have  been  de- 
scribed. 


CHAPTER    IV» 

ELECTRICITY, 

209.  Electricity  is  one  of  those  subtle  agents  without 
weight  or  form,  that  appear  to  be  diffused  through  all 
nature,  existing  in  all  substances  without  affecting  their 
volume  or  their  temperature,  or  giving  any  indication  of 
its  presence  when  in  a  latent,  or  ordinary  state.  When, 
however,  it  is  liberated  from  .this  repose,  it  is  capable  of 

QuK§TiONS.-^What  influence  do  the  three  principles  of  the  solar"  ray  eSert  on  vegetation  ? 
"What  is  electricity  ? 


ELECTRICITY.  131 

producing  the  most  sudden  and  destructive  effects,  or  of 
exerting  powerful  influences  by  a  quiet  and  long-continued 
action. 

We  are  unable  to  say  whether  electricity  is  a  material  substance,  a  property 
of  matter,  or  the  vibration  of  an  ether.  The  general  opinion  at  the  present 
day,  however,  is,  that  electricity,  like  light  and  heat,  is  the  result  of  some 
modification,  or  vibration  of  that  subtile  ethereal  medium  which  pervades  all 
space,  and  whick  is  capable  of  moving  with  various  degrees  of  facility  through 
the  pores  of  even  the  densest  substances. 

The  language  which  is  almost  universally  adopted  in  describing  electrical 
phenomena,  is  based  upon  the  supposition  that  electricity  is  a  form,  or  kind 
of  matter,  since  by  the  use  of  this  hypothesis,  the  leading  facts  of  the  science 
may  be  clearly  and  simply  set  forth. 

210.  Electricity    and   Chemical    Action,— The  relation 
which  exists  between  the  force  of  electricity  and  the  opera- 
tions of  chemical  affinity  is  most  intimate  ;  and  according 
to  some  authorities  electricity  and  chemical  affinity  are 
merely  different  manifestations  of  the  same  agent 

211.  Excitation  of  Electricity—  Electricity  may  be  ex- 
cited,  or  called   into   activity  by  mechanical  action,  by 
chemical  action,  by  heat,  and  by  magnetic  influence. 

Why  the  means  above  enumerated  should  develop  electricity,  or  excite  it 
from  a  neutral  condition,  is  &  matter  at  present  wholly  inexplicable. 

212.  Two  Conditions  of  Electricity.— Electricity  in  the 
act  of  becoming  free,  as  when  excited  by  friction,  or  when 
evolved  from  a  galvanic  battery,  appears  to  separate  into 
two  forces,  or,  as  it  is  generally  termed,  into  two  kinds  of 
electricity.     These  two  forces  are  identical  in  their  nature 
and  equal  in  power,  but  opposite  and  contrary  in  their  ac- 
tion.    When   they   meet,   they  do  not  unite  to  form  a 
double  electrical  force,  but  they  mutually  neutralize  and 
destroy  the  power  of  each  other. 

The  existence  and  action  of  these  two  forces,  or  kinds  of  electricity,  may  bo 
demonstrated  by  the  following  simple  experiment : — If  we  take  a  dry  glass 
rod,  rub  it  well  with  silk,  and  present  it  to  a  light  pith  ball,  or  feather,  P, 

QUESTIONS.— What  do  we  know  concerning  the  real  nature  t>f  this  agent  ?  What  is  the 
relation  between  electricity  and  chemical  action  ?  How  may  electricity  be  excited  ?  In 
what  manner  does  electricity,  on  being  set  free,  display  itself?  What  is  the  character  of 
the  two  forces,  or  kinds  of  electricity  ?  How  may  the  existence  and  action  of  the  two 
kinds  of  electricity  be  demonstrated  ? 


132  PRINCIPLES     OF     CHEMISTRY. 

Fig.  59,  suspended  from  a  support  by  a  silk  thread,  the  ball  or  feather  will  be 
attracted  toward  the  glass,  as  seen  at  GL  After  it  has  adhered  to  it  a  moment, 
it  win  fly  off;  or  be  repelled,  as  P'  from  G'.  The 
same  thing  will  also  happen  if  sealing-wax  b© 
rubbed  with  dry  flannel,  and  a  like  experiment 
made. 

If,  however,  the  action  of  the  glass  and  the 
wax  be  compared  together,  a  remarkable  differ- 
ence between  the  two  will  immediately  manifest 
itself,  for  when  the  glass  repels  the  ball  the  seal- 
ing-wax will  attract  it  most  strongly,  and  when 
the  wax  repels,  the  glass  attracts  in  like  manner; 

«o  that  if  we  suspend  a  light  pith  ball,  or  feather,  by  a  silk  thread,  as  in  Fig. 
60,  and  present  a  stick  of  excited  sealing-wax,  S,  on  one  side, 
and  a  tube  of  excite(i  •g]asSf  ^  on  tlie  other^  the  bali  wilj 

commence  vibrating  like  a  pendulum  from  one  to  the  otherr 
being  alternately  attracted  and  repelled  by  each,  the  one  at- 
tracting when  the  other  repels.  We  therefore  conclude  that 
the  electricities  excited  in  the  glass  and  wax  are  different 

la  order  to  distinguish  the  two  opposite 
forces  or  conditions  of  electricity  from  each 
other,  that  force  which  is  obtained  from  the  glass  has  "been 
termed  vitreous,  or  positive  electricity  ;  and  that  from  the 
wax>  resinous,  or  negative  electricity. 

While  the  terms  vitreous  and  resinous  are  now  rarely  used,  those  of  posi- 
tive and  negative  are  somewhat  unfortunate,  since  they  almost  unavoidably 
convey  to  the  learner  the  impression  that  the  one  force  is  stronger  or  more 
potent  than  the  other,  whereas  the  negative  electricity  has  as  positive  an  ex- 
istence and  as  substantial  power  as  the  opposite  electricity. 

Electricity  may  be  excited  in  all  bodies.  There  are  no  exceptions  to  this 
fact,  but  electricity  is-  developed  in  some  bodies  with  great  ease,  and  in  others- 
with  great  difficulty.  In  no  case,  however,  can  electricity  of  one  kind  be 
excited  without  setting  free  a  corresponding  amount  of  electricity  of  the 
other  kmd  •  hence,  when  electricity  is  excited  by  friction,  the  rubber  always 
exhibits  the  one,  and  the  body  nibbed,  the  other. 

213.  Fundamental  Law  of  Electricity.— The  funda- 
mental law  which  governs  the  relation  of  the  two  forces 
of  electricity  to  each  other  may  be  expressed  as  follows  : 

Like  electricities  repel  each  other,  unlike  electricities 
attract  each  other. 

QUESTIONS. — By  what  names  do  we  distinguish  the  two  forces,  or  kinds  of  electricity? 
Why  is  the  use  of  the  terms  positive  and  negative  unfortunate  ?  Can  one  electricity  be 
developed  independently  of  the  other  ?  What  is  the  great  fundamental  law  of  electricity  ? 


ELECTKICITY.  133 

Thus,  if  two  substances  are  charged  with  positive  electricity,  they  repel 
each  other ;  two  substances  charged  with  negative  electricity  also  repel  each 
other ;  but  if  one  is  charged  with  positive  and  the  other  with  negative  elec- 
tricity, they  attract  each  other. 

The  attraction  which  the  two  opposite  electricities  have  for  each  other  is 
very  great,  and  their  tendency  is,  therefore,  constantly  to  combine  together. 
From  such  combination  latent,  or  quiescent  electricity  results. 

214.  Electrified  and  Non-Electrified  Bodies,— When  a 
body  holds  its  own  natural  quantity  of  electricity  undis- 
turbed, it  is  said  to  he  non-electrified. 

When  an  electrified  body  touches  one  that  is  non-elec- 
trified, the  electricity  contained  in  the  former  is  trans- 
ferred in  part  to  the  latter. 

Thus,  on  touching  the  end  of  a  suspended  silk  thread  with  a  piece  of  ex- 
cited wax  or  glass,  electricity  will  pass  from  the  wax  or  glass  into  the  silk, 
and  render  it  electrified ;  and  the  silk  will  exhibit  the  effects  of  the  electricity 
imparted  to  it,  by  moving  toward  any  object  that  may  be  placed  near  it. 

215.  Conductors    and   Non-Conductors. —  Bodies   differ 
greatly  in  the  freedom  with  which  they  allow  electricity 
to  pass  over  or  through  them.     Those  substances  which 
facilitate  its  passage  are  called  conductors  ;  those  thaTre- 
tard,  or  almost  prevent  it,  are  called  non-conductors. 

No  substance  can  entirely  prevent  the  passage  of  electricity,  nor  is  there 
any  which  does  not  oppose  some  resistance  to  its  passage. 

Of  all  bodies,  the  metals  are  the  most  perfect  conductors  of  electricity  j 
charcoal,  the  earthr  water,  moist  air,  most  liquids,  except  oils,  and  the  human 
body,  are  also  good  conductors  of  electricity. 

Gum  shellac  and  gutta  percha  are  the  most  perfect  non-conductors  of  elec- 
tricity; sulphur,  sealing-wax,  resin,  and  all  resinous  bodies,  glass,  silk, 
feathers,  hairr  dry  wool,  dry  air,  and  baked  wood,  are  also  non-conductors. 

Electricity  always  passes  by  preference  over  the  best  conductors. 

216.  Insulation, — When  a  conductor  of  electricity  is 
surrounded  on  all  sides  by  non-conducting  substances,  it 
is  said  to  be  insulated  ;  and  the  non-conducting  substances 
which  surround  it  are  called  insulators. 

"When  a  conducting  body  is  insulated,  it  retains  upon  its  surface  the  elec- 
tricity communicated  to  it,  and  in  this  condition  it  is  said  to  be  charged  with 
electricity. 

QUESTIONS. — Illustrate  it.  When  is  a  body  said  to  be  electrified,  and  when  non-electri- 
fied? What  are  conductors  and  non-conductors  of  electricity?  What  substances  are 
good  conductors?  What  are  bad  conductors?  When  is  a  conductor  said  to  be  insulated  ? 
When  charged? 


134  PKINCIPLES     OF     CHEMISTRY. 

217.  Telocity  of  Electricity,— The  velocity  with  which 
the  influence  of  electricity  passes  through  good  conduc- 
tors is  so  great,  that  the  most  rapid  motion  produced  by 
art  appears  to  be  actual  rest  when  compared  to  it.     Some 
authorities  have  estimated  that  frictional  electricity  will 
pass  through  copper  wire  at  the  rate  of  288,000  miles  in 
a  second   of  time — a  velocity  greater  than  that  of  light. 
The  results  obtained,  however,  by  the  United  States  Coast 
Survey,  with  galvanic  electricity  and  iron  wire,  show  a 
velocity  of  from  15,000  to  20,000  miles  per  second. 

The  terms  "  electric  fluid'1  and  "  electric  current,"  which  are  frequently  em- 
ployed in  describing  electrical  phenomena)  are  calculated  to  mislead  the  stu- 
dent into  the  supposition  that  electricity  is  known  to  be  a  fluid,  and  that  it 
flows  in  a  rapid  stream  along  a  conductor.  Such  terms,  it  should  be  un- 
derstood, are  founded  merely  on  an  assumed  analogy  between  the  electric 
force  and  a  fluid  substance.  The  nature  of  that  force,  however,  is  unknown, 
and  whether  its  transmission  be  in  the  form  of  a  current,  or  by  vibrations,  is 
undetermined.* 

218.  Galvanic,  or  Voltaic  Electricity,— Electricity  ex- 
cited or  produced  by  the  chemical  action  of  two  or  more 
dissimilar  substances  upon  each  other,  is  termed  Galvanic, 
or  Voltaic  Electricity,  and  the  department  of  physical 
science  which  treats  of  this  form  of  electrical  disturbance 
is  called  Galvanism. 

The  most  simple  method  of  illustrating  the  production  of  galvanic  electricity 
is  by  placing  a  piece  of  silver  (as  a  coin)  on  the  tongue,  and  a  piece  of  zinc 
underneath.  So  long  as  the  two  metals  are  kept  asunder  no  effect  will  bo 
noticed,  but  when  their  ends  are  brought  together  a  distinct  thrill  will  pass 
through  the  tongue,  a  metallic  taste  will  diffuse  itself,  and,  if  the  eyes  are 
dosed,  a  simsation  of  light  will  be  evident  at  the  same  moment 

This  result  is  owing  to  a  chemical  action  which  is  developed  the  moment 


*  In  a  discussion  which  took  place  some  years  since  at  a  meeting  of  the  British  Associa- 
tion for  the  Advancement  of  Science,  respecting  the  nature  of  electricity,  Professor  Fara- 
day expressed  his  opinion  as  follows: — "  There  was  a  time  when  I  thought  I  knew  some- 
thing about  the  matter ;  but  the  longer  I  live,  and  the  more  carefully  I  study  the  subject1 
the  more  convinced  I  am  of  my  total  ignorance  of  the  nature  of  electricity." 

44  After  such  an  avowal  as  this,"  says  Mr.  Bakewell,  4'  from  the  most  eminent  electrician 
of  the  age,  it  is  almost  useless  to  say  that  any  terms  which  seem  to  designate  the  form  of 
electricity  are  merely  to  be  considered  as  convenient  conventional  expressions." 


QUESTIONS.— What  is  the  velocity  of  electricity?  What  is  understood  by  the  use  of  the 
word  current,  as  applied  to  electricity  ?  What  is  galvanic,  or  voltaic  electricity  ?  What 
ia  the  most  simple  method  of  illustrating  its  production  ?  To  what  is  this  result  owing  ? 


ELECTRICITY.  135 

the  two  metals  touch  each  other.  The  saliva  of  the  tongue  acts  chemically 
upon,  or  oxydizes  a  portion  of  the  zinc,  which  excites  electricity,  for  no  chem- 
ical action  ever  takes  place  without  producing  electricity.  Upon  bringing 
the  ends  of  the  two  metals  together,  a  slight  current  passes  from  one  to  the 
other. 

219.  Discovery  of  Galvanic  Electricity, — The  produc- 
tion of  electricity  by  the  chemical  action  of  two  metals 
when  brought  in  contact,  was  first  noticed  by  Galvani, 
a  professor  of  anatomy  at  Bologna,  Italy,  in  1790. 

His  attention  was  directed  to  the  subject  in  the  following  manner : — Hav- 
ing occasion  to  dissect  several  frogs,  he  hung  up  their  hind  legs  on  some  cop- 
per hooks,  until  he  might  find  it  necessary  to  use  them  for  illustration.  In 
this  manner  ho  happened  to  suspend  a  number  of  the  copper  hooks  on  an 
iron  balcony,  when,  to  his  great  astonishment,  the  limbs  were  thrown  into 
violent  convulsions.  On  investigating  the  phenomenon,  he  found  that  the 
mere  contact  of  dissimilar  metals  with  the  moist  surfaces  of  the  muscles  and 
nerves,  was  all  that  was  necessary  to  produce  the  convulsions. 

FIG.  Gl. 


This  singular4  action  of  electricity,  first  noticed  by  Galvani,  may  be  experi- 
mentally exhibited  without  difficulty.  Fig.  Gl  represents  the  extremities  of 
a  frog,  with  the  upper  part  dissected  in  such  a  way  as  to  exhibit  the  nerves 

Q0ESTiON8.—When  and  how  Was  galvanic  electricity  discovered  ?  tto*  toay  the  phe- 
nomenon first  noticed  by  Galvani.  be  experimentally  repeated  ? 


136  PRINCIPLES    OF     CHEMISTRY. 

of  the  legs,  and  a  portion  of  the  spinal  marrow.  If  we  now  take  two  thin 
pieces  of  copper  and  zinc,  C  Z,  and  place  one  under  the  nerves,  and  the  other 
in  contact  with  the  muscles  of  the  leg,  we  shall  find  that  so  long  as  the  two 
pieces  of  metal  are  separated,  so  long  will  the  limbs  remain  motionless  ;  but 
by  making  a  connection,  instantly  the  whole  lower  extremities  will  be  thrown 
into  violent  convulsions,  quivering  and  stretching  themselves  in  a  manner 
too  singular  to  describe.  If  the  wire  is  kept  closely  in  contact,  these  phen- 
omena are  of  momentary  duration,  but  are  renewed  every  time  the  contact  is 
made  and  broken, 

Galvani  attributed  these  movements  of  the  muscles  to  a  kind  of  nervous 
fluid  pervading  the  animal  system,  similar  to  the  electric  fluid,  which  passed 
from  the  nerves  to  the  muscles,  as  soon  as  the  two  were  brought  in  commu- 
nication with  each  other,  by  means  of  the  metallic  connection.  He  therefore 
called  the  supposed  fluid  animal  electricity. 

220.  The  Voltaic  Pile. — 'The  experiments  of  Galvani  were  re- 
peated by  Volta,  an  eminent  Italian  philosopher,  who  found  that  no  electrical 
or  nervous  excitement  took  place  unless  a  communication  between  the  muscles 
and  the  nerves  was  made  by  two  different  metals,  as  copper  and  iron,  or 
copper  and  zinc.  He  also  observed  that  all  the  effects  noticed  could  be  pro- 
duced in  a  much  higher  degree  by  using  a  number  of  pieces  of  different 
•p..  />9  metals  and  a  fluid,  or  a  substance  moistened  with 

a  fluid.  He  accordingly  arranged  a  series  of  cop- 
per and  zinc  plates  in  a  pile  with  cloths  wet  in  a 
saline  or  acid  liquid  between  them,  as  is  repre- 
sented in  Fig.  62.  The  series  commenced  with  a 
zinc  plate,  upon  which  was  placed  a  copper  plato 
of  the  same  size,  and  on  that  a  circular  piece  of 
cloth  previously  soaked  in  water  slightly  acidu- 
lated. On  the  cloth  was  laid  another  plate  of 
zinc,  then  copper,  and  again  cloth,  and  so  on  in 
succession,  until  a  pile  of  fifty  series  of  alternate 
metal  plates  and  moistened  cloths  was  formed,  the 
terminal  plate  of  the  series  at  one  end  being  cop- 
per and.  at  the  other  end  zinc.  Such  an  apparatus 
received  the  name  of  a  "  Voltaic  Pile,1'  and  its  ef- 
fects were  soon  seen  to  be  of  an  electrical  char- 
acter. 

For  instance,  if  the  two  ends  or  terminal  plates  of  the  pile  were  touched, 
one  with  each  hand  previously  moistened,  a  sensation  similar  to  that  of  an 
electric  shock  was  experienced.  If  the  two  ends  were  connected  by  means 
of  metallic  wires,  sparks  could  be  obtained,  shocks  communicated,  anb  many 
other  electrical  effects  produced. 

QtrBSTTONB.— To  what  did  Galvani  attribute  the  results  by  him  noticed  ?  What  conclu- 
sion waa  arrived  at  by  Volta?  What  discovery  did  Volta  make?  Describe  the  roltaic 
pile. 


ELECTRICITY.  137 

221.  Results   of  Galvani's  and  Volta's  Discoveries. — 

Such  is  an  outline  of  one  of  the  greatest  and  most  remarkable  discoveries  of 
modern  times — a  discovery  which  illustrates  in  a  striking  manner  the  im- 
portance of  cultivating  correct  habits  of  observation,  and  of  rightly  estimating 
the  relations  which  exist  between  a  cause  and  its  effect.  The  attention  be- 
stowed by  Galvani  on  the  simple  circumstance  of  the  twitching  of  a  frog's 
legs  in  1790,  led  to  the  discovery  of  the  voltaic  pile  in  1800,  a  modification  of 
which  constitutes  the  present  galvanic  battery.  Since  the  last  named  period 
the  progress  of  discovery  has  been  most  rapid,  embracing  the  whole  science 
of  electro-magnetism,  electro-metallurgy,  the  application  of  electricity  to 
chemical  analysis,  to  the  production  of  intense  heat  and  light,  to  the  recording 
of  time,  to  the  determination  of  longitudes,  and  finally,  to  the  almost  instan- 
taneous communication  of  intelligence  by  means  of  the  telegraph. 

Volta  considered  that  electricity  was  produced  by  simple  contact  of  dis- 
similar metals,  positive  electricity  being  evolved  from  the  one,  and  negative 
from  the  other.  It  is  now  generally  believed  that  chemical  action,  taking 
place  between  the  surfaces  in  contact,  is  the  sole  cause  of  exciting  and  con- 
tinuing the  electric  currents. 

222.  Fundamental  Principle  of  Galvanic  Electricity,— 
The  fundamental  principle  which  forms  the  basis  of  the 
science  of  galvanic  electricity  is  as  follows  : 

Any  two  metals,  or  more  generally,  any  two  different 
bodies  which  are  conductors  of  electricity,  when  placed  in 
contact,  develop  electricity  by  chemical  action — positive 
electricity  flowing  from  the  body  which  is  acted  upon  most 
powerfully,  and  negative  electricity  from  the  other. 

223.  Electro-positive  and  Negative  Elements, — In  gen- 
eral, that  substance  which  is  acted  upon  most  easily  is 
termed   the  electro-positive  element ;  and  the  other  the 
electro-negative  element. 

The  electrical  force  or  power  generated  in  this  way  is 
called  the  electro-motive  force. 

Different  bodies  placed  in  contact  manifest  different 
electro-motive  forces,  or  develop  different  quantities  of 
electricity. 

Bodies  capable  of  developing  electricity  by  contact  may  be  arranged  in  a 


QUESTIONS — What  have  been  the  results  of  Galvani's  and  Volta's  discoveries  ?  Whafc 
did  Volta  suppose  to  be  the  origin  of  the  electricity  of  the  pile  ?  What  is  now  believed  on 
this  subject?  What  is  the  fundamental  principle  of  galvanic  electricity?  What  are  elec- 
tro-positive and  electro-negative  elements?  What  is  understood  by  the  term  electro- 
motive force  ?  How  may  bodies  capable  of  exciting  electro-motive  force  be  classed  ? 


138 


PRINCIPLES    OF     CHEMISTRY. 


FIG.  63. 


N 


series  in  such  a  manner  that  any  one  placed  in  contact  with  another  holding 
a  lower  place  in  the  series,  will  receive  the  positive  fluid,  and  the  lower  one 
the  negative  fluid ;  and  the  more  remote  they  stand  from  each  other  in  the 
order  of  the  series,  the  more  decidedly  will  the  electricity  be  developed  by 
their  contact. 

The  most  common  substances  used  for  exciting  galvanic  electricity  may  be 
arranged  in  such  a  series  as  follows : — zinc,  lead,  tin,  antimony,  iron,  brass, 
copper,  silver,  gold,  platinum,  black  lead  or  graphite,  and  charcoal 

Thus,  zinc  and  lead,  when  brought  in  contact,  will  produce  electricity,  but 
it  will  be  much  less  active  than  that  produced  by  the  union  of  zinc  and  iron, 
or  the  same  metal  and  copper,  and  the  last  less  active  than  zinc  and  platinum 
or  zinc  and  charcoal. 

224.  Zamboni's    Pile  , — According  to  the  principles  above  explained, 
a  perfectly  dry  pile,  known  from  its  inventor  as  Zamboni's  pile,  may  be  con- 
structed of  sheets  of  gilded  paper  and  sheet  zinc.     If 
several  thousand  of  these  be  packed  together  in  a 
glass  tube,  so  that  their  similar  metallic  faces  shall  all 
look  the  same  way,  and  be  pressed  tightly  together 
at  each  end  by  metallic  plates,  it  will  be  found  that 
one  extremity  of  the  pile  is  positive  and  the  other 
negative.     Such  a  series  will  last  more  than  twenty 
years,  but  it  requires  as  many  as  10,000  pairs  to  af- 
ford sparks  visible  hi  daylight 

Fig.  63  represents  a  pair  of  these  piles,  so  arranged 
as  to  produce  what  has  been  called  a  perpetual  mo- 
tion. Two  piles,  P  N,  are  placed  hi  such  a  position 
that  the  positive  extremity  of  one  pile  is  opposite  and 
near  to  the  negative  extremity  of  the  other.  Be- 
tween them  a  light  pendulum  is  placed,  vibrating  on 
an  axis  and  insulated  on  a  glass  pillar.  This  pen- 
dulum is  alternately  attracted  to  one  and  then  to  the 
other,  and  thus  rings  two  little  bells  connected  with 
the  positive  and  negative  poles. 
In  a  similar  manner,  voltaic  piles  have  been  constructed  entirely  of  vege- 
table substances,  without  resorting  to  the  use  of  any  metal,  by  placing  discs 
of  beet-root  and  walnut-wood  in  contact  "With  such  a  pile,  and  a  leaf  of 
grass  as  a  conductor,  convulsions  in  the  muscles  of  a  dead  frog  are  said  to 
have  been  produced.  Other  experimentalists  have  formed  voltaic  piles  wholly 
of  animal  substances. 

225.  Practical  Production  of  Galvanic  Electricity.— In 
the  production  of  galvanic  electricity  for  practical  pur- 
poses, it  is  necessary  to  have  a  combination  of  three  dif- 

QTJESTIONS Describe  the  dry,  or  Zamboni's  pile.  May  a  voltaic  pile  be  produced  en- 
tirely of  vegetable  or  animal  substances  ?  What  arrangement  is  necessary  for  the  practi- 
cal production  of  galvanic  electricity  ? 


ELECTRICITY. 


139 


FIG.  64. 


ferent  conductors,  or  elements,  one  of  which  must  be 
solid  and  one  fluid,  while  the  third  may  be  either  solid  or 
fluid. 

The  process  usually  adopted  is  to  place  between  two  plates  of  different 
kinds  of  metal  a  liquid  capable  of  exciting  some  chemical  action  on  one  of  tho 
plates,  while  it  has  no  action,  or  a  different  action  upon  the  other.  A  com- 
munication is  then  formed  between  the  two  plates. 

226.  Galvanic  Circuit, — When  two  metals  capable  of 
exciting  electricity  are  so  arranged  and  connected  that  the 
positive  and  negative  electricities  can  meet  and  flow  in 
opposite  directions,  they  are  said  to  form  a  galvanic  cir- 
cuit, or  circle.     Such  an  arrangement  is  very  generally 
termed,  also,  a  simple  galvanic  battery. 

A  very  simple,  and  at  the  same  time 
an  active  galvanic  circuit  may  be  formed 
by  an  arrangement  as  represented  in 
Tig.  64.  C  and  Z  are  thin  plates  of 
copper  and  zinc  immersed  in  a  glass 
vessel  containing  a  very  weak  solution 
of  sulphuric  acid  and  water.  So  long 
as  the  two  metals  do  not  touch  each 
other,  there  will  be  but  slight  chemical 
action,  and  consequently  little  or  no 
electricity  evolved ;  but  on  bringing  the 
two  ends  of  the  metal  strips  together,  or 
by  causing  metallic  contact  by  a  con- 
nection of  wires,  X  and  W,  a  galvanic 
circuit  will  be  formed,  positive  elec- 
tricity passing  from  the  zinc  through  the  liquid  to  the  copper,  and  from  tho 
copper  along  the  conducting  wires  to  the  zinc,  as  indicated  by  the  arrows  in 
the  figure.  A  current  of  negative  electricity  at  the  same  time  traverses  the 
circuit  also,  from  the  copper  to  the  zinc,  in  an  opposite  direction. 

227.  Theory    of  a   Simple    Circuit  — In  the  formation  of  a  gal- 
vanic circuit,  by  the  employment  of  two  metals  and  a  liquid,  the  chemical  ac- 
tion which  gives  rise  to  the  electricity  takes  place  through  a  decomposition 
of  the  liquid. 

When  a  plate  of  zinc  and  one  of  copper  are  immersed  in  water  acidulated  with 
sulphuric  acid,  the  elements  of  the  water,  oxygen  and  hydrogen,  are  separated 
from  each  other,  in  consequence  of  the  greater  attraction  which  the  oxygen 
has  for  tho  zinc.  The  oxygen,  therefore,  unites  with  the  zinc,  and  by  so  doing 


QUESTIONS. — "What  is  a  galvanic  circuit,  or  simple  galvanic  battery  ?  Desaribe  the  con- 
struction of  such  a  circuit.  What  is  the  origin  of  the  electricity  evolved  in  a  circuit 
composed  of  two  metals  and  one  liquid  ?  Describe  the  theoretical  action  of  such  a  circuit  ? 


140  PRINCIPLES     OF     CHEMISTRY. 

excites,  or  develops  electricity  in  the  metal.  But  as  one  kind  of  electricity 
can  not  be  evolved  without  bringing  an  equal  quantity  of  the  other  into  ac- 
tivity, the  act  which  develops  negative  electricity  in  the  metal,  instantaneously 
develops  positive  electricity  in  the  liquid.  It  would  naturally  be  supposed, 
t'.iat  as  the  two  .opposite  electricities  have  a  strong  attraction  for  each  other, 
fiat  they  would  again  unite,  and  restore  the  equilibrium ;  such,  however, 
f. 'om  some  unexplained  reason,  is  not  the  case ;  but  the  electrical  and  chem- 
ical changes  are  so  connected,  that  unless  the  equilibrium  is  restored,  the 
action  between  the  metal  and  the  liquid  will  stop  as  soon  as  a  certain  quan- 
tity of  electricity  has  accumulated.  If,  under  these  circumstances,  the  copper 
plate  which  is  immersed  in  the  liquid,  but  not  acted  upon  by  it,  be  brought 
in  contact  with  the  zinc,  it  will  serve  as  a  conductor,  and  will  convey  the 
positive  electricity  accumulated  in  the  liquid  to  the  zinc,  restore  the  equili- 
brium of  the  two  electricities,  and  cause  the  action  between  the  liquid  and  the 
zinc  to  recommence.  With  the  commencement  of  the  flow  of  positive  elec- 
tricity from  the  liquid  to  the  copper,  and  from  the  copper  to  the  zinc,  a  cur- 
rent of  negative  electricity  will  tend  to  flow  in  the  opposite  direction,  or  from 
the  zinc  to  the  copper,  and  from  the  copper  to  the  liquid.* 

228.  Direction  of  the  Current, — In  all  cases,  the  direc- 
tion of  the  current  is  dependent  on  the  direction  of  the 
chemical  action. 

The  positive  electricity  always  sets  out  from  the  metal  most  acted  upon  by 
the  exciting  liquid,  which  may  be,  therefore,  called  the  generating  or  posi- 
tive plate.  It  traverses  the  liquid  toward  the  less  affected  metal,  which  forms 
the  negative,  or  conducting  plate,  and  from  this  the  force  is  transferred  to  the 
•wire,  or  other  conducting  medium,  between  the  two  plates ;  thence  it  passes 
back  again  to  the  generating  plate.  In  this  way  the  circuit  is  completed,  and 
unless  this  circulation  can  take  place,  all  the  phenomena  of  galvanic  action 
will  be  suspended. 

The  electrical  condition  of  the  plates  of  copper  and  zinc  as  above  described, 
it  should  be  understood,  applies  only  to  those  portions  of  the  two  metals 
which  are  immersed  in  the  liquid.  Those  parts  which  are  out  of  the  liquid, 
and  in  the  air,  are  in  an  exactly  opposite  condition.  Thus  the  end  of  the  zinc 
in  the  acid  is  -f-,  of  positive,  while  that  in  the  air  is  — ,  or  negative.  The 
electrical  state  of  the  two  ends  of  the  copper  is  exactly  the  reverse. 

If,  in  the  arrangement  above  described,  some  liquid  which  acts  upon  the 
copper  in  preference  to  the  zinc,  as  ammonia,  had  been  used,  the  electrical 


*  In  every  voltaic  current  it  is  assumed  that  a  quantity  of  negative  electricity,  equal  to 
that  of  the  positive  set  in  motion,  is  proceeding  along  the  conducting'medium  in  a  direc- 
tion opposite  to  that  in  which  the  positive  electricity  is  traveling ;  but  in  order  to  avoid 
confusion,  whenever  the  direction  of  the  current  is  mentioned,  the  direction  of  the  posi- 
tive electricity  is  alone  referred  to. 

QTTESTIONS.— What  influences  the  direction  of  the  current  ?  What  determines  the  elec- 
trical condition  of  the  immersed  metals  ? 


ELECTKICITY.  141 

condition  of  the  two  metals,  and  the  direction  of  the  flow  of  electricity,  would 
have  been  reversed. 

Although  two  metal  plates  are  usually  employed  in  a  simple  galvanic 
circuit,  only  one  of  them  is  active  in  the  excitement  of  electricity,  the  other 
plate  serving  merely  as  a  conductor  to  collect  the  force  generated.  A  metal 
plate  is  generally  used  for  this  purpose,  because  metals  conduct  electricity 
much  better  than  other  substances  exposing  an  equal  surface  to  the  fluids 
in  which  they  are  immersed ;  but  other  conductors  may  be  used,  and  when 
a  proportionately  larger  surface  is  exposed  to  compensate  for  inferior  con- 
ducting power,  they  answer  as  well,  and  in  some  instances  better,  than  metal 
plates.  Thus  charcoal  is  very  often  employed  in  the  place  of  copper,  and  a 
very  hard  material  obtained  from  the  interior  of  gas  retorts,  "  gas-carbon," 
is  considered  one  of  the  best  conductors. 

Two  metals  are  not  absolutely  essential  to  the  formation  of  a  simple  gal- 
vanic current.  A  current  may  be  obtained  from  one  metal  and  two  liquids, 
provided  the  liquids  are  such  that  a  stronger  chemical  action  takes  place  on 
one  sido  of  the  metal  plate  than  on  the  other. 

229.  Poles  of  a  Galvanic  Battery,— The  two  metals 
forming  the  elements  of  the  battery  are  generally  connected 
by  copper  wires  ;  the  ends  of  these  wires,  or  the  terminal 
points  of  any  other  connecting  medium  used,  are  called 
the  poles  of  the  battery. 

Thus,  when  zinc  and  copper  plates  are  used,  the  end  of  the  wire  conveying 
positive  electricity  from  the  copper  would  be  the  positive  pole,  and  the  end  of 
the  wire  conveying  negative  electricity  from  the  zinc  plate  would  be  the 
negative  pole.  Faraday  describes  the  poles  of  the  battery  as  the  doors  by 
which  electricity  enters  into  or  passes  out  of  the  substance  suffering  decom- 
position, and  in  accordance  with  this  view  he  has  given  to  the  positive  pole 
the  name  of  anode,  or  ascending  way,  and  to  the  negative  pole  the  name  of 
cathode,  or  descending  way. 

The  manifestations  of  electricity  will  be  most  appa- 
rent at  that  point  of  the  circuit  where  the  two  currents 
of  positive  and  negative  electricity  meet. 

"When  the  two  wires  connecting  the  metal  plates  of  a  battery  are  brought 
in  contact,  the  galvanic  circuit  is  said  to  be  closed.  No  sign  of  electrical  ex- 
citement is  then  visible ;  the  action,  nevertheless,  continues.  The  opposite 
electricities  collected  at  the  poles,  in  particular,  neutralize  each  other  perfectly 
on  meeting ;  every  trace  of  electricity  must  therefore  vanish  if  a  fresh  .quan-  * 
tity  were  not  continually  produced  by  the  continuance  of  the  chemical  action. 

QUESTIONS. — What  is  the  necessity  of  two  metals  in  a  galvanic  circuit  ?  Under  what 
circumstances  can  some  other  substance  be  substituted  in  place  of  the  copper  ?  What 
are  the  poles  of  a  galvanic  battery  ?  What  is  the  meaning  of  the  terms  anode  and 
cathode  ?  At  what  point  of  a  galvanic  circuit  will  the  manifestation  of  electricity  be  most 
apparent?  When  is  the  galvanic  circuit  said  to  be  closed ? 


142  PRINCIPLES     OF     CHEMISTRY. 

230.  Compound  Circuit, — The  electricity  developed  by 
a  simple  galvanic  circuit,  whether  it  be  composed  of  two 
metals  and  a  liquid,  or  any  other  combination,  is  exceed- 
ingly feeble.  Its  power  can,  however,  be  increased  to  any 
extent  by  a  repetition  of  the  simple  combinations. 

The  discovery  of  this  fact  was  first  made  by  Yolta,  and  applied  by  him  in 
the  voltaic  pile  before  described. 

FIG.  65. 


Fig.  65  represents,  in  its  simplest  form,  the  construction  of  a  compound 
galvanic  circuit,  by  the  union  of  a  number  of  simple  circuits.  Each  glass 
contains  one  zinc  and  one  copper  plate,  which  are  not  immediately  connected 
together  as  in  a  simple  circuit ;  but  every  zinc  plate  is  connected  with  the 
copper  plate  of  the  preceding  glass  by  a  copper  wire  or  band.  In  the  figure, 
the  copper  plate  and  the  direction  of  the  positive  current  is  represented  by  tho 
sign  -J-,  and  the  zinc  plate  and  the  negative  current  by  the  sign  — . 

In  a  compound  galvanic  circuit,  like  the  one  represented  in  Fig.  65,  the 
positive  electricity  which  the  fluid  in  the  first  vessel  acquires  from  the  plate 
of  zinc  exposed  to  its  action,  is  taken  up  by  the  copper  plate  and  transferred 
to  the  second  zinc  plate  in  the  second  vessel,  by  means  of  its  metallic  con- 
nection. This  transmits  it,  together  with  what  itself  generates,  to  the  liquid 
of  the  second  vessel.  From  this  the  double  force  is  passed  to  the  next  cop- 
per, and  by  it  to  the  third  zinc,  which  it  touches,  and  so  on,  every  succeeding 
alternation  being  productive  of  a  further  increase  in  the  quantity  of  the  elec- 
tricity developed.  A  current  of  negative  electricity  may  in  like  manner  be 
supposed  to  flow  in  an  opposite  direction,  its  quantity  augmenting  with  each 
successive  pair  of  plates.  This  action,  however,  would  stop  unless  an  outlet 
were  given  to  the  accumulated  electricity  by  establishing  a  communication 
between  the  positive  and  negative  poles  of  the  battery,  by  means  of  wirea 
attached  to  the  extreme  plate  at  each  end.  When  these  are  brought  into 
contact,  the  galvanic  circuit  is  completed,  and  the  electricities  meet  and  neu- 
tralize each  other,  producing  the  various  electrical  phenomena.  The  electric 
current  continues  to  flow  uninterruptedly  in  the  circuit  so  long  as  the  chem- 
ical action  lasts. 

QUESTIONS.— What  is  the  electrical  power  of  a  simple  circuit  ?  How  may  it  be  increased  ? 
Describe  the  construction  of  a  compound  circuit  ?  In  what  manner  does  it  accumulate 
electricity  ? 


ELE  CTRICIT  Y. 


143 


The  simple  and  compound  voltaic  circuits  in  practical  use,  which  in  ordi- 
nary language  are  both  designated  as  galvanic  batteries,  differ  considerably 
in  form  and  efficiency.  The  general  principle  of  construction  in  all,  however, 
is  the  same  as  that  of  the  original  voltaic  pile. 

231.  The    Trough    Battery  , — One  of  the  earliest  forms  contrived 
is  known  as  the  Trough  Battery,  represented  in  Fig.  66.    It  consists  of  a 
trough  of  wood  divided  into  water-  ]?IG.  66. 

tight  cells,  or  partitions,  each  cell  ^^^2^^-y—^.^  B^,'J.  -~% 
being  arranged  to  receive  a  pair  of 
zinc  and  copper  plates.  The  plates 
are  attached  to  a  bar  of  wood,  and 
connected  with  one  another  by  me- 
tallic wires,  in  such  a  way  that  every 
copper  plate  is  connected  with  the 
zinc  plate  of  the  next  cell.  The  bat- 
tery is  excited  by  means  of  dilute 
sulphuric  acid  poured  into  the  cells, 
and  the  current  of  electricity  is  di- 
rected by  wires  soldered  to  the  ex- 
treme plates.  When  the  battery  is  not  in  use  the  plates  may  be  raised 
from  the  trough  by  means  of  the  wooden  bar. 

The  battery  by  which  Sir  Humphrey  Davy  effected  his  splendid  chemical 
discoveries  was  of  this  form,  and  consisted  of  two  thousand  double  plates  of 
copper  and  zinc,  each  plate  having  a  surface  of  thirty-two  square  inches. 
Now,  however,  by  improved  arrangements,  we  can  produce  with  ten  or 
twenty  pairs  of  plates,  effects  every  way  superior. 

232.  Smee's    Battery, — The    most    easily  managed 
form  of  galvanic  battery  at  present  used  is  that  invented  by 
Mr.  Smee,  and  known  as  Smee's  battery.     (See  Fig.  67.)     It 
consists  of  a  plate  of  silver  coated  with  platinum,  suspended 
between  two  plates  of  zinc,  z  z,  the  surfaces  of  which  last  have 
been  coated  with  mercury,  or  amalgamated,  as  it  is  called. 
The  three  are  attached  to  a  wooden  bar,  which  serves  to  sup- 
port the  whole  in  a  tumbler,  G,  partially  filled  with  a  weak 
solution  of  sulphuric  acid  and  water.     The  wires,  or  poles  for 
directing  the  current  of  electricity  are  connected  with  the  zinc 
aud  platinum  plates  by  small  screw-cups,  S  and  A. 

233.  Amalgamation    of  Zinc . — The  introduction  of  the  process 
of  amalgamating,  or  coating  the  zinc  plates  of  a  galvanic  circuit  with  mer- 
cury, constituted  an  improvement  of  great  value.     In  the  original  form  of 
the  galvanic  battery,  constructed  of  copper  and  ordinary  metallic  zinc,  tho 
waste  of  the  latter  metal  by  the  action  of  the  exciting  acid  upon  it  was  very 


FiG.  67, 


QUESTIONS.— Describe  the  trough  battery.  What  is  the  construction  of  Smee's  battery  ? 
What  is  understood  by  the  amalgamation  of  the  zinc?  What  benefit  results  from  this 
operation? 


144 


PRINCIPLES     OF     CHEMISTRY. 


FIG.  68. 


great ;  but  by  using  amalgamated  zinc  this  waste  is  diminished  in  an  extra- 
ordinary degree,  without  at  the  same  time  diminishing  the  production  of 
electricity.  All  improved  batteries  are,  therefore,  constructed  with  amalga- 
mated zinc. 

234.  Sulphate  of  Copper  Battery  , — Another  form  of  battery, 
called  the  sulphate  of  copper  battery,  from  the  fact  that  a  solution  of  sul- 
phate of  copper  (blue  vitriol)  is  used  as  the  exciting  liquid,  is  represented  by 
Fig.  68.  It  consists  of  two  concentric  cylinders  of  cop- 
per, C,  tightly  soldered  to  a  copper  bottom,  and  a  zinc 
cylinder,  Z,  fitting  in  between  them.  Two  screw- cups 
for  holding  the  connecting  wires  are  attached,  one  to 
the  outer  copper  cylinder,  and  the  other  to  the  zinc. 

The  principal  imperfection,  of  the  galvanic  battery  is 
the  want  of  uniformity  in  its  action.     In  all  the  various 
forms,  the  strength  of  the  electric  current  excited  con- 
stantly decreases  from  the  moment  the  battery  action 
commences.     In  the  sulphate  of  copper  battery,  espe- 
cially, the  power  is  reduced  in  a  comparately  short  time 
to  almost  nothing.     Tlu's  is  chiefly  owing  to  the  circum- 
stance, that  the  metallic  plates  soon  become  coated  with  the  products  of  the 
chemical  decomposition,  the  result  of  the  chemical  action  whereby  the  elec- 
tricity is  developed. 

This  difficulty  is  obviated  in  a  great  degree  by  the  use  of  a  diaphragm,  or 
a  porous  and  permeable  partition  between,  the  two  metallic  plates,  which  al- 
lows a  free  contact  of  the  liquid  on  both  sides  within  its  pores,  but  prevents 
the  solid  products  of  the  chemical  action  from  passing  from  one  metallic  plate 
to  the  other.  Bladder,  leather,  clay,  porce- 
lain, cloth,  etc.,  have  been  used  for  this  pur- 
pose. 

235.  Daniel's  Constant  Battery, 
constructed  according  to  the  above  described 
principle,  and^  represented  by  Fig.  69,  main- 
tains an  effective  galvanic  action  longer  than 
any  other.  The  outer  case,  C,  consists  of  a 
cell,  or  cylinder  of  copper,  which  is  so  con- 
structed as  to  retain  liquids,  and  is  filled  with  a 
solution  of  sulphate  of  copper,  B,  acidulated 
with  one  eighth  of  its  bulk  of  sulphuric  acid. 
The  solution  is  kept  saturated  with  the  salt 
by  means  of  crystals  of  sulphate  of  copper, 
D,  which  rest  upon  the  perforated  shelf,  F. 
In  the  center  of  the  cell  is  placed  a  tube  of  porous  earthen- ware,  E,  filled  with 


FlG.  69. 


QUESTIONS.— Describe  the  sulphate  of  copper  battery.  What  is  the  principal  imperfee- 
ion  of  the  galvanic  battery  ?  How  is  it  obviated  ?  What  is  the  construction  of  Daniel's 
battery  ? 


ELECTRICITY. 


145 


FIG.  70. 


an  acid  solution,  A,  which  consists  of  one  part  of  oil  of  vitriol  diluted  with 
seven  parts  of  water.  A  rod  of  zinc,  Z,  is  placed  in  this  tube.  On  making  a 
metallic  communication  between  the  zinc  rod  and  the  copper  cell,  a  voltaic 
current  is  established. 

236.  Grove's    Battery . — One  of  the  most  efficient  batteries  is  that 
known  as  Grove's  battery,  from  its  inventor,  and  is  the  form  generally  used 
for  telegraphing,  and  other  purposes  in  which  powerful  galvanic  action  is  re- 
quired.    It  is  constructed  upon  the  same  general  principle  as  Daniel's  battery, 
and  consists  of  a  plain  glass  tumbler,  in  which  is  placed  a  cylinder  of  amal- 
gamated zinc,  with  an  opening  on  one  side  to  allow  a  free  circulation  of  the 
liquid.     "Within  this  cylinder  is  placed  a  porous  cup,  or  cell  of  earthenware, 
in  which  is  suspended  a  strip  of  platinum  fastened  to  the*  end  of  a  zinc  arm 
projecting  from  the  adjoining  zinc  cylinder.     The  porous  cup  containing  the 
platinum  is  filled  with  strong  nitric  acid,  and  the  outer  vessel  containing  the 
zinc  with  weak  sulphuric  acid.    Tig.  70  represents  a  series  of  these  cups, 
arranged  to  form  a  compound  cir- 
cuit, with  their  terminal  poles,  P 

and  Z.  This  form  of  battery  is 
objectionable  on  account  of  the 
corrosive  character  of  the  acids 
employed,  and  the  deleterious  va- 
pors that  arise  from  it  when  in 
action. 

In  what  is  known  as  Bunsen's 
Carbon  Battery,  a  cylinder  of 
carbon  is  substituted,  on  the 
ground  of  economy,  in  place  of 
the  platinum  plates  of  Grove's  battery. 

237.  Resistances   to   the  Circulation  of  the  Galvanic 
Current . — The  amount  of  force  or  of  electricity  which  circulates  in  a  gal- 
vanic circuit  does  not  depend  wholly  upon  the  energy  of  the  chemical  action 
which  is  exerted  between  the  generating  metal  and  the  exciting  liquid. 
"  The  current  experiences  a  retardation  or  resistance  from  the  very  conduc- 
tors by  which  its  influence  is  transmitted ;  just  as  in  the  transmission  of 
mechanical  force  in  an  arrangement  of  machinery,  the  intervention  of  the 
pivots  and  levers  which  are  required  for   its   conveyance  introduces  ad- 
ditional frictioa  and  additional  weight,  which  are  required  to  be  overcome 
or  moved,  and  which  thus  diminish  the  efficient  power  of  the  machine." — 
MILLER. 

The  resistances  of  the  galvanic  current  arise  from  the  imperfect  conduct- 
ing power  of  the  liquid  which  is  employed  to  excite  it,  and  of  the  plates, 
wires,'  etc.,  the  resistance  offered  by  the  liquid  being  the  most  considerable 


QUESTIONS.— Describe  Grove's  battery.  Is  the  electricity  of  a  galvanic  circuit  always 
in  proportion  to  the  chemical  action  exerted?  What  are  the  resistances  it  experiences? 
To  what  are  these  resistances  proportional  ? 

7 


146  PRINCIPLES     OF     CHEMISTRY. 

of  the  two.  The  further  the  plates  are  removed  from  each  other  in  the  liquid, 
and  tiie  longer  the  column  of  imperfectly  conducting  matter  which  the  elec- 
tricity is  obliged  to  traverse,  the  greater  the  resistance.  The  same  thing  is 
also  true  of  the  conducting  wire.  A  wire  one  tenth  of  an  inch  in  diameter, 
will  for  equal  lengths  offer  four  times  the* resistance  of  a  wire  two  tenths,  or 
one  fifth  of  an  inch  thick. 

238.  Characteristics  of  Ordinary  and  Galvanic  Elec- 
tricity.— Electricity   in   its    ordinary   manifestations,    as 
when  developed  by  friction  or  by  an  electrical  machine, 
exhibits  itself  in  sudden  and  intermitted  shocks,  accom- 
panied with  a  sort  of  explosion  ;  galvanic  electricity,  or 
electricity  produced  by  chemical  action,  is,  on  the  contrary, 
a  steady  flowing  current. 

The  electricity  evolved  by  a  single  galvanic  circle  is 
great  in  quantity,  but  weak  in  intensity. 

The  electricity,  on  the  contrary,  produced  by  friction, 
or  that  of  a  thunder-cloud,  is  small  in  quantity,  but  of 
high  tension,*  or  intensity. 

These  two  qualities  may  be  compared  to  heat  of  different  temperatures.  A 
gallon  of  water  at  a  temperature  of  100°  has  a  greater  quantity  of  heat  than 
a  pint  at  200°  ;  but  the  heat  of  the  latter  is  more  intense  than  that  of  the 
former.  Again,  in  the  phosphorescence  of  the  sea,  which  often  spreads  over 
thousands  of  miles,  we  have  an  illustration  of  light  very  feeble  ia  intensity, 
but  enormous  in  quantity. 

239.  Quantity  and  Intensity,  how  Measured  . — We  meas- 
ure the  quantity  of  electricity  in  many  ways ;  but  most  conveniently  by  the 
amount  of  any  chemical  compound  which  it  can  decompose.     A  machine  or 
battery,  for  example,  which,  when  arranged  so  as  to  decompose  water,  evolves 
from  it  four  cubic  inches  of  oxygen  and  hydrogen  in  one  minute,  is  furnishing 
twice  the  quantity  of  electricity  supplied  by  an  apparatus  which  evolves  only 
two  cubic  inches  of  the  gases  in  the  same  time. 

Tho  intensity  of  electricity  ia  less  easily  measured ;  but  it  is  comparatively 
indicated  by  the  ease  with  which  it  can  travel  through  bad  conductors ;  by 


*  "  Tension  is  merely  a  synonyme  for  intensity,  which  originated  in  the  hypothesis  of 
electricity  being  an  elastic  fluid,  which  might  be  regarded  as  existing  in  a  thunder-cloud, 
or  on  the  conductor  of  a  friction-machine  in  a  state  of  condensation  or  compression,  like 
high-pressure  steam  struggling  to  escape  from  a  boiler,  or  air  seeking  to  force  its  way  out 
of  the  chamber  of  an  air-gun.  The  word  tension  has  been  preferred  to  intensity!  simply 
on  account  of  its  brevity,  and  its  convenience  in  forming  a  double  noun  with  electricity. 

QTTESTIONS.— What  are  the  characteristic  differences  between  galvanic  and  ordinary 
electricity?  To  what  may  quantity  and  intensity  be  compared?  How  are  theae  two 
qualiiiea  measured  ?  What  is  understood  by  the  term  tension  ? 


ELECTRICITY.  147 

its  power  to  overcome  energetic  chemical  affinity,  such  as  that  which  binds 
together  the  elements  of  water ;  by  the  length  of  space  across  which  it  can 
pass  through  dry  air  (as  in  the  case  of  a  lightning  flash  striking  a  tree  from  a 
great  distance);  by  the  attractions  and  repulsions  it  produces  in  light  bodies; 
and  by  the  severity  of  the  shock  it  occasions  to  living  animals. 

Galvanic  electricity  will  traverse  a  circuit  of  2,000  miles  of  wire,  rather 
than  make  a  short  circuit  by  overleaping  a  space  of  resisting  air  not  exceed- 
ing one  hundredth  part  of  an  inch.  Frictional  electricity,  on  the  other  hand, 
will  force  a  passage  across  a  considerable  interval,  in  preference  to  taking  a 
long  circuit  through  a  conducting  medium. 

The  assertion  is  within  bounds,  that  the  whole  electricity  of  a  destructive 
thunder-storm  would  not  suffice  for  the  electro-gilding  of  a  single  pin — so  in- 
significant is  its  amount.  A  small  copper  wire,  dipped  into  an  acid  along 
with  a  wire  of  zinc,  would  evolve  more  electricity  in  a  few  seconds  than  the 
largest  friction  electrical  machine,  kept  constantly  revolving,  would  furnish 
in  many  weeks.  No  shock,  on  the  other  hand,  would  be  occasioned  by  the 
electricity  from  the  immersed  wires ;  nor  would  it  produce  a  spark,  or  de- 
compose water — so  low  is  its  intensity.  A  galvanic  battery  of  many  plates 
will,  however,  produce  electricity  of  sufficient  intensity  to  kill  a  large  animal, 
and  produce  other  effects  analogous  to  lightning. 

Electricity  of  intensity  then,  or  tension-electricity,  is 
electricity  characterized  by  the  greatness  of  its  intensity — 
or  whose  intensity  is  greater  than  its  quantity.  Electricity 
of  quantity,  on  the  other  hand,  has  its  quantity  greater 
than  its  intensity. 

The  intensity  diminishes  as  the  quantity  increases ;  but  the  ratio  which  the 
one  bears  to  the  other  differs  through  a  very  wide  scale,  so  that  a  knowledge 
of  the  degree  of  the  one  does  not  often  enable  us  to  predicate  the  amount  of 
the  other.  Practically,  we  have  no  difficulty  in  reducing  both  to  a  minimum, 
or  in  exalting  the  one  whilst  we  reduce  the  other;  but  we  can  not  at  once 
exalt  both  intensity  acd  quantity.  The  discovery  of  a  method  of  effecting 
this  will  make  a  new  era  in  the  science  ;  and  admit  of  the  most  important 
applications  to  the  useful  arts. 

240.  Practical  Applications  of  Electricity  of  Quan- 
tity and  Intensity  — In  the  arts,  it  depends  much  upon  the  purpose 
to  which  electricity  is  to  be  applied  whether  it  should  be  chosen  great  in 
quantity,  or  great  in  intensity.  If  the  chemist  desires  to  analyze  a  gaseous 
mixture  by  exploding  it,  he  will  use  an  electrical  machine  to  supply  a  mo- 
mentary spark  of  great  intensity.  But  the  electro-plater,  who  has  constantly 
to  decompose  a  compound  of  gold  or  silver,  employs  a  small  voltaic  battery — 
which  furnishes  great  quantities  of  electricity  of  considerable  intensity.  The 

QUESTIONS. — Illustrate  the  differences  bet-ween  quantity  and  intensity.  What  definition 
maybe  given  of  the  two  ?  What  relation  exists  between  them  ?  What  are  their  practical 
applications  ? 


148  PRINCIPLES    OF    CHEMISTRY. 

electric  light  requires  both  quantity  and  intensity  to  be  very  great.  The 
electric  telegraph  demands  great  quantity,  but  the  intensity  need  not  be  very 
high. 

241.  Electro-chemical  Decomposition,— When  a  current 
of  galvanic  electricity  is  made  to  pass  through  a  compound 
liquid,  composed  of  one  conducting  and  one  non-conduct- 
ing substance,  its  tendency  is  to  decompose  and  separate 
it  into  its  constituent  parts. 

242.  Decomposition    of  Water . — The  most  remarkable  illustra- 
tion of  this  power  is  to  be  found  in  the  decomposition  of  water.     This  sub- 
stance is  composed  of  two  gases,  oxygen  and  hydrogen,  united  hi  the  propor- 
tions of  one  measure  of  the  former  to  two  of  the  latter.     When  two  gold  or 
platinum  wires,  connected  with  the  opposite  ends  of  a  galvanic  battery,  are 
placed  in  water  at  a  short  distance  from  each  other,  the  water  is  decomposed, 
the  hydrogen  arising  in  bubbles  from  the  negative  pole  of  the  battery,  and 

.  71.  the  oxygen  from  the  positive  pole.  When  two  glass  tubes 
are  placed  over  the  platinum  poles,  as  is  represented  in  Fig. 
71,  we  can  collect  the  bubbles  as  they  rise,  the  volume  of  the 
hydrogen  being  twice  as  great  as  that  of  the  oxygen. 

When  copper  wires,  or  the  wires  of  metals  which  tend 
strongly  to  unite  with  oxygen  are  employed,  gas  escapes  from 
one  wire  only ;  whilst  if  platinum  or  gold  wires  be  used,  gas 
is  evolved  from  both.  In  the  first  case,  the  oxygen  combines 
with  the  copper  or  other  oxydizable  metal,  and  forms  an 
oxyd,  which  is  dissolved  by  the  liquid,  and  therefore  hydro- 
gen alone  escapes ;  in  the  second  case,  both  gases  are  evolved, 

since  neither  platinum  or  gold  have  sufficient  chemical  affinity  for  oxygen  to 

combine  with  it  at  the  moment  of  its  liberation. 

243.  Electrodes . — The  term  electrode  is  often  used  to  designate  the 
poles  of  a  galvanic  battery.     It  is  especially  applied  in  those  cases  in  which 
the  connecting  wires  of  a  circuit  are  terminated  with  strips  of  platinum,  gold, 
charcoal,  or  some  other  good  conducting,  non-oxydizable  substance. 

244.  Theory   of    Electro-chemical    Decomposition. — 
Scientific  men  are  not  fully  agreed  upon  the  explanation  of  the  phenomenon 
of  chemical  decomposition  by  means  of  the  galvanic  current.     A  general  idea 
of  what  takes  place  may  perhaps  be  best  gained  from  what  is  called  the 
electro-chemical  theory.     According  to  this,  chemical  attractions,  which  wo 
distinguish  by  the  name  of  affinity,  and  electrical  attractions  depend  on  the 
same  cause,  acting  in  one  case  on  atoms,  and  in  the  other  on  masses  of  mat- 
ter.    Every  atom  of  matter  is  regarded  as  charged  in  respect  to  all  other 


QUESTIONS. — What  is  the  influence  of  the  electric  current  in  producing  electro-chemical 
decomposition  ?  How  is  this  illustrated  in  the  decomposition  of  water  ?  What  are  elec- 
trodes ?  What  is  the  theory  of  the  decomposing  action  of  galvanic  electricity  ? 


ELECTRICITY.  149 

atoms,  with  either  positive  or  negative  electricity.  In  the  case  of  water, 
hydrogen  is  the  electro-positive  element  and  oxygen  the  electro-negative  ele- 
ment. It  has  been  already  shown  that  bodies  in  opposite  electrical  states  are 
attracted  by  each  other.  Hence,  when  the  poles  of  a  galvanic  battery  are 
immersed  in  water,  the  negative  pole  will  attract  the  positive  hydrogen,  and 
the  positive  pole  the  negative  oxygen.  If  the  attractive  force  of  the  two 
electricities  generated  by  the  battery  is  greater  than  the  attractive  force  which 
unites  the  two  elements,  oxygen  and  hydrogen,  together  in  the  water,  the 
compound  will  be  decomposed.  Upon  the  same  principle  other  compound 
substances  may  be  decomposed,  by  employing  a  greater  or  less  amount  of 
electricity.  In  this  way  Sir  Humphrey  Davy  made  the  discovery  that  potash, 
soda,  lime,  and  other  bodies,  were  not  simple  in  then*  nature,  as  had  pre- 
viously been  supposed,  but  compounds  of  a  metal  with  oxygen. 

This  theory,  as  presented,  is  not  received  as  strictly  in  accordance  with  the 
fact.  Recent  experiments  of  Faraday  have  proved  that  the  electricity  which 
decomposes,  and  that  which  is  evolved  by  the  decomposition  of  a  certain 
quantity  of  matter,  are  alike.  Thus,  water  is  composed  of  oxygen  and  hydro- 
gen ;  now,  if  the  electrical  power  which  holds  a  grain  of  water  in  combina- 
tion, or  which  causes  a  grain  of  oxygen  and  hydrogen  to  unite  in  the  right 
proportions  to  form  water,  could  be  collected  and  thrown  into  a  voltaic  cur- 
rent, it  would  be  exactly  the  quantity  required  to  produce  the  decomposition 
of  a  grain  of  water  or  the  liberation  of  its  elements,  oxygen  and  hydrogen. 

The  quantity  of  electricity,  however,  which  is  required  to  effect  chemical 
decomposition  is  enormous.  Faraday  estimates  the  amount  of  electricity  re- 
quired to  decompose  a  single  grain  of  water  to  be  equal  to  that  evolved  by  a 
powerful  flash  of  lightning. 

245.  Limits  of  the  Decomposing  Action, — Decomposition 
by  the  agency  of  the  electric  current  takes  place  solely  at 
those  points  where  the  electricity  enters  and  leaves  the 
liquid. 

Thus,  when  a  portion  of  water,  for  example,  is  subjected  to  decomposition 
in  a  glass  vessel  with  parallel  sides,  oxygen  is  disengaged  at  the  positive 
electrode,  and  hydrogen  at  the  negative,  the  gases  being  perfectly  pure  and 
unmixed.  If,  while  the  decomposition  is  rapidly  proceeding,  the  intervening 
water  is  carefully  examined,  not  the  slightest  disturbance  or  movement  of 
any  kind  will  be  perceived ;  nothing  like  currents  in  the  liquid,  or  transfer  of 
gas  from  one  part  to  the  other  can  be  detected ;  and  yet  two  portions  of 
water,  separated  by  an  interval  of  four  or  five  inches,  may  be  respectively 
evolving  pure  hydrogen  and  oxygen.  Now,  since  we  know  that  every  par- 
ticle of  water  is  composed  of  oxygen  and  hydrogen  in  the  exact  ratio  of  two 

QUESTIONS.—  Explain  the  decomposition  of  water.  What  fact  has  been  proved  by  the 
experiments  of  Faraday?  What  is  the  relative  quantity  of  electricity  required  to  effect 
chemical  decomposition  ?  At  what  points  of  the  galvanic  circuit  does  the  decomposing 
action  take  place  ?  Illustrate  this.  In  what  respect  is  this  action  contrary  to  what  might 
be  naturally  expected  ? 


150  PRINCIPLES    OF     CHEMISTRY. 

measures  of  the  latter  to  one  of  the  former,  it  would  naturally  be  supposed 
that  the  electric  current  having  separated  the  oxygen  at  one  point,  hydro- 
gen would,  having  lost  its  combining  element,  also  escape  at  the  same  point. 
This,  however,  is  not  the  case,  and  great  difficulty  has  been  experienced  in 
accounting  for  it. 

The  difficulty  will  be  more  evident,  says  Mr.  Hunt,  if  we  take  the  experi- 
ment on  a  larger  scale ;  for  example,  if  on  one  side  of  a  wide  river  the 
positive  pole  is  placed  in  the  water,  and  the  negative  pole  on  the  other,  we 
shall  still  have — the  battery  being  of  sufficient  power — oxygen  given  off  on 
one  side  of  the  river,  while  hydrogen  would  be  evolved  at  the  other. 

The  following  is  the  received  explanation  : — The  arrangement  of  the  par- 
ticles constituting  a  line  or  layer  of  water  between  the  poles  of  a  galvanic 
circuit  may  be  represented  as  follows,  the  positive  atom,  hydrogen,  of  each 
particle  of  water  being  turned  by  the  influence  of  the  electricity  toward  the 
negative  pole,  and  the  negative  atom,  oxygen,  toward  the  positive  pole — 

Positive  pole  —  OH,   OH,    OH,    OH,    OH,    OH  —  Negative  pole. 

The  same  thing  may  be  also  illustrated  in  Fig.  72,  where  the  particles  of 
p  ^  water  are  supposed  to  be  spherical,  the  shaded 

portion  of  each  sphere  representing  the  hydro- 
gen half  of  the  particle,  and  the  light  portion 


A 


333333^ 


B  If  the  positive  pole  is  placed  on  the  left  and 
the  negative  on  the  right,  oxygen  passes  off 
from  the  first,  and  hydrogen  from  the  last ;  if 

we  reverse  the  poles,  the  order  of  the  decomposition  is  changed  also.  It  is 
not,  however,  to  be  supposed  that  when  H.  is  liberated  from  0.  at  the  nega- 
tive pole,  that  the  0.  of  that  particle  passes  over  along  the  line  to  the  positive 
pole ;  but  the  view  taken  is,  that  as  soon  as  the  atom  of  oxygen  loses  its 
hydrogen,  it  combines  with  the  atom  of  hydrogen  of  the  next  particle  of 
water,  and  a  new  particle  of  water  is  reproduced.  The  oxygen  of  the  second 
particle  being  thereby  liberated,  combines  with  the  hydrogen  of  the  next 
particle  of  water,  and  thus  the  decomposition  and  recomposition  is  continued 
on  to  the  end  of  the  series.  Resorting  again  to  symbols,  No.  1  will  repre- 
sent the  state  of  things  before  any  change  has  been  effected,  and  No.  2  the 
change  after  the  circuit  is  complete — 

No.  1.  +  0  H,  OH,  OH,  OH,  0  H  - 

No.  2.  +  0,  H  0,  H  0,  H  0,  H  0,  H  — 

It  should  also  be  borne  in  mind,  that  the  changes  described  are  not  suc- 
cessive, but  simultaneous  at  each  end  of  the  series  of  particles,  and  at  all 
intervening  points  in  the  line  of  the  series. 

246.  Electrolysis  and  Electrolytes,— The  process  of  re- 
solving compounds  into  their  constituents  by  electricity  is 

QUESTIONS.— What  is  supposed  to  actually  occur  in  the  decomposition  of  water  ?  What 
is  electrolysis  ? 


ELECTRICITY.  151 

termed  Electrolysis,  and  a  body  susceptible  of  such  de- 
composition is  termed  an  Electrolyte. 

No  elementary  substance  can  be  an  electrolyte ;  for  from  the  nature  of  the 
process,  compounds  alone  are  susceptible  of  electrolysis.  Electrolysis  occurs 
only  whilst  the  body  is  in  the  liquid  state.  The  free  mobility  of  the  particles 
which  form  the  body  undergoing  decomposition  is  a  necessary  condition  of 
electrolysis,  since  the  operation  is  always  attended  by  a  transfer  of  the  com- 
ponent particles  of  the  electrolyte  in  opposite  directions. 

The  passage  of  a  current  of  electricity  through  the  liquid  used  in  the  cells 
or  cups  of  a  galvanic  circuit  depends  upon  the  decomposition  of  its  particles,  in 
the  same  manner  as  in  the  case  of  water.  No  fluid,  therefore,  which  is  not 
an  electrolyte,  or  in  other  words,  which  is  not  capable  of  being  decomposed, 
is  suitable  for  exciting  a  battery. 

247.  Electro-chemical  Order  of  the  Elements,— All  the 
elementary  substances,  according  as  they  appear  at  the  posi- 
tive or  negative  poles  of  a  galvanic  circuit,  have  been  classi- 
fied into  electro-positive  and  electro-negative  substances. 

In  the  following  table  the  most  important  of  the  elements  are  arranged  in 
the  order  of  their  relative  negative  and  positive  properties,  the  most  iu  tensely 
negative  element  being  placed  at  the  top  of  the  series,  and  the  most  intensely 
positive  at  the  bottom : 

ELECTBO-NEGATIYE. — Oxygen. 

Sulphur. 

Nitrogen. 

Chlorine. 

Fluorine. 

Carbon. 

Phosphorus. 

Hydrogen. 

Gold. 

Platinum. 

Mercury. 

Silver. 

Copper. 

Tin. 

Lead. 

Iron, 

Zinc. 

Sodium. 

Potassium. — ELECTRO-POSITIYE. 

QUESTIONS.— What  are  electrolytes?  Why  can  not  an  elementary  substance  be  an  elec- 
trolyte ?  What  conditions  are  necessary  for  electrolysis  ?  What  fluids  only  are  capable 
of  exciting  a  galvanic  battery?  How  may  the  elementary  substances  be  classed  as  re- 
spects their  electrical  properties? 


152  PRINCIPLES     OF     CHEMISTRY. 

In  this  arrangement,  each  metal  is  positive  as  respects  all  that  stand  before 
it,  and  negative  as  respect  those  that  succeed  it.  Oxygen  is  negative  in  every 
combination,  and  potassium  appears  to  be  uniformly  positive.  Hydrogen  is 
highly  positive  when  compared  with  oxygen  and  chlorine,  but  with  metals  it 
always  exhibits  negative  electric  energy. 

248.  Electro -metallurgy,  or  electrotyping,  is  the  art  or 
process  of  depositing,  from  a  metallic  solution,  through 
the  agency  of  galvanic  electricity,  a  coating  or  film  of 
metal  upon  some  other  substance.* 

The  process  is  based  on  the  fact,  that  when  a  galvanic 
current  is  passed  through  a  solution  of  some  metal,  as  of 
sulphate  of  copper  (sulphuric  acid  and  oxyd  of  copper), 
decomposition  takes  place  ;  the  metal,  being  electro-posi- 
tive, attaches  itself  in  a  metallic  state  to  the  negative 
pole,  or  to  any  substance  that  may  be  attached  to  the 
negative  pole  ;  while  the  oxygen,  or  other  electro-nega- 
tive element  before  in  combination  with  the  metal,  goes 
to,  and  is  deposited  on  the  positive  pole. 

In  this  way  a  medal,  a  wood-engraving,  or  a  plaster  cast,  if  attached  to  the 
negative  pole  of  a  battery,  and  placed  in  a  solution  of  copper  opposite  to  the 
positive  pole,  will  be  covered  with  a  coating  of  copper ;  if  the  solution  con- 
tains gold  or  silver  instead  of  copper,  the  substance  will  be  covered  with  a 
coating  of  gold  or  silver  in  the  place  of  copper. 

The  thickness  of  the  deposit,  provided  the  supply  of  the  metallic  solution 
be  kept  constant,  will  depend  on  the  length  of  tune  the  object  is  exposed 
to  the  influence  of  the  battery. 

In  this  way,  a  coating  of  gold  thinner  than  the  thinnest  gold-leaf  can  be 
laid  on,  or  it  may  be  made  several  inches  or  feet  in  thickness,  if  desired. 

The  usual  arrangement  for  conducting  the  electrotype  process  is  represented 
by  Fig.  13.  It  consists  of  a  trough  of  wood,  or  an  earthen  vessel,  containing 
the  solution  of  the  metal,  the  decomposition  of  which  is  desired — for  example, 
sulphate  of  copper.  Two  wires,  one  connected  with  the  positive,  and  the 
other  with  the  negative  pole  of  a  battery,  Q,  are  extended  along  the  top  of 
the  trough,  and  supported  on  rods  of  dry  wood,  B  and  D.  The  medal,  or 
other  article  to  be  coated,  is  attached  to  the  extremity  of  the  negative  wire 


*  The  general  name  of  electro-metallurgy  includes  all  the  various  processes  and  results 
which  different  inventors  and  manufacturers  have  designated  as  galvano-plastic,  electro- 
plastic,  galvano-type,  electro-typing,  and  electro-plating  and  gflding. 

QUESTIONS.— What  substance  is  always  negative?  What  one  always  positive?  Define 
electro-metallurgy.  Upon  what  is  the  process  based  ?  How  is  the  thickness  of  the  de- 
posit regulated  ?  Describe  the  arrangement  for  conducting  the  electrotype  process. 


ELECTKICIT  Y. 


153 


and  a  plate  of  metallic  copper  to  the  end  of  the  positive  wire.  When  both 
of  these  are  immersed  in  the  liquid,  the  action  commences— the  sulphate  of 
copper  is  decomposed — the  copper  being  deposited  on  the  medal  attached 
to  the  negative  pole,  and  the  oxygen,  before  combined  with  it,  on  the  copper 
plate  attached  to  the  positive  pole,  forming  oxyd  of  copper.  As  the  with- 
drawal of  the  metal  from  the  solution  goes  on,  the  oxyd  of  copper  thus  formed 

PiGh  73, 


unites  with  the  sulphuric  acid  which  is  liberated  in  the  solution,  and  forma 
sulphate  of  copper.  This  dissolving  in  the  liquid,  maintains  it  at  a  constant 
strength. 

The  sole  object  of  attaching  a  plate  of  metallic  copper  to  the  positive  pole 
is  to  thus  preserve  the  strength  of  the  solution  of  sulphate  of  copper.  If  the 
positive  pole  had  terminated  with  a  plate  of  platinum  or  gold,  the  action 
would  have  commenced  equally  well,  but  the  oxygen  liberated  from  the  cop- 
per, through  its  want  of  affinity  to  either  the  platinum  or  the  gold,  would 
have  escaped  as  gas,  and  the  solution  gradually  becoming  weaker  from  the 
withdrawal  of  its  elements,  the  electro-plating  action  would  cease.  When  the 
operator  judges  that  the  deposit  on  the  medal  is  sufficiently  thick,  he  removes 
it  from  the  trough,  and  detaches  the  coating.  The  deposit  is  prevented  from 
adhering  to  the  medal  by  rubbing  its  surface  in  the  first  instance  With  oil,  or 
black-lead,  and  if  it  is  desired  that  any  part  of  the  surface  Should  be  left  un- 
coated,  that  portion  is  covered  with  wax,  varnish,  or  some  other  non-con- 
ductor, 

In  this  way  a  most  perfect  reversed  copy  of  the  medal  is  obtained— that  is, 
the  elevations  and  depressions  of  the  original  are  reversed  in  the  copy*  To 
obtain  a  fac-simile  of  the  original,  the  electrotype  cast  is  Subjected  to  a  repe- 
tition of  the  process. 

In  general,  it  is  found  more  convenient  to  mold  the  object  to  be  repro- 
duced in  wax,  or  Plaster  of  Paris.  The  surface  of  this  cast  is  then  brushed 
over  with  black-lead  to  render  it  a  conductor,  and  the  metal  deposited  directly 
upon  it,  The  deposit  obtained  will  then  exactly  resemble  the  original  ob- 
ject. * 


154  PRINCIPLES    OF    CHEMISTRY. 

The  pages  and  engravings  in  the  book  before  the  reader  are  illustrations  of 
the  perfection  and  practical  application  of  the  electrotype  process.  The  en- 
gravings were  first  cut  upon  wood-blocks,  and  then,  in  combination  with  the 
ordinary  type,  formed  into  pages.  Casts  of  the  whole  in  wTax  were  then 
made,  and  an  electrotype  coat  of  copper  deposited  upon  them,  and  from  the 
copper  plates  so  formed  the  book  was  printed.  The  great  advantage  of  this 
is,  that  the  copper  being  harder  than  the  ordinary  type  metal,  is  more  durable, 
and  resists  the  wear  of  printing  from  its  surface  for  a  longer  period. 

The  improvement  effected  by  electro-metallurgy  in  engraving  is  very  great. 
"When  a  copper  plate  is  engraved,  and  impressions  printed  off  from  it,  only  the 
first  few,  called  "proof  impressions,"  possess  the  fineness  of  the  engraver's 
delineation.  The  plate  rapidly  wears  and  becomes  deteriorated.  But  by  the 
electrotype  process,  the  original  plate  can  at  once  be  multiplied  into  a  great 
many  plates  as  good  as  itself,  and  an  unlimited  number  of  the  finest  impres- 
sions procured. 

In  this  way  the  map  plates  of  the  Coast  Survey  of  the  United  States,  some 
of  which  require  the  labor  of  the  engraver  for  years,  and  cost  thousands  of 
dollars,  are  reproduced — the  original  plate  being  never  printed  from. 

The  metals  upon  which  an  adherent  coating  of  silver  or  gold  is  most 
readily  deposited  are  brass,  copper,  bronze,  and  German  silver.  The  articles 
to  be  plated  or  gilded  must  be  carefully  cleansed  from  all  adhering  greasy 
matters  by  boiling  them  in  a  weak  alkaline  solution,  and  then  rubbing  them 
with  chalk,  rotten-stone,  etc,  The  articles  are  then  carefully  washed,  at- 
tached to  a  clean  copper  wire,  and  immersed  in  the  silvering  solution.  The 
deposit  is  hastened  by  keeping  the  solution  moderately  warm,  especially  at 
the  commencement  of  the  process.  The  articles,  when  plated,  have  a  dead 
White,  or  chalky  appearance,  but  by  burnishing  they  assume  the  brilliant  lus- 
ter of  polished  silver.* 

249.  Protection  of  Metals  from  Corrosion.— When  two 
metals  which  are  positive  and  negative  in  their  electrical 
relations  to  each  other,  are  brought  in  contact,  a  galvanic 
action  takes  place  which  promotes  chemical  change  in  the 
positive  metal,  but  opposes  it  in  the  negative  metal. 

Thus,  when  sheets  of  zinc  and  copper  immersed  in  dilute  acid  touch  each 
other,  the  zinc  oxydizes  or  rusts  more,  and  the  copper  less  rapidly,  than 


*  The  teacher,  for  experiment,  Can  best  illustrate  the  deposition  of  metals  by  electro- 
chemical action  in  the  following  manner  : — Put  a  piece  of  silver  in  a  glass  containing  a 
solution  of  sulphate  of  copper,  and  into  the  same  glass  insert  a  piece  of  zinc.  No  change 
•will  take  place  in  either  metal  so  long  as  they  are  kept  apart ;  but  as  soon  as  they  touch, 
the  copper  will  be  deposited  upon  the  silver,  and  if  it  be  allowed  to  remain,  the  part  im. 
mersed  will  b^completely  covered  with  copper,  which  will  adhere  so  firmly  that  mere 
tubbing  alone  will  not  remove  it. 

QUESTIONS. — How  has  the  electrotype  process  affected  the  art  of  engraving  ?  What  are 
the  peculiarities  of  the  process  of  electro-plating  and  gilding  ?  Under  what  circumstances 
can  metals  be  protected  from  chemical  action  ?  Illustrate  this. 


ELECTRICITY.  155 

without  contact.  Iron  nails,  if  used  in  fastening  copper  sheathing  to  vessels, 
rust  much  quicker  than  when  in  other  situations,  not  in  contact  with  the 
copper.  The  reason  of  this  is,  that  the  two  metals,  in  consequence  of  the 
electricity  developed  by  their  union,  are  placed  in  opposite  electrical  condi- 
tions. The  copper  which  is  ordinarily  positive,  is  rendered  negative  by  the 
contact  of  the  zinc,  or  iron  ;  it,  therefore,  is  not  only  entirely  wanting  in  at- 
traction for  the  negative  corroding  oxygen  of  the  air,  or  water,  on  the  prin- 
ciple that  bodies  similarly  electrified  repel  each  other,  but  even  has  a  tendency 
to  abandon  any  oxygen  with  which  it  may  have  previously  combined.  The 
zinc  and  iron,  on  the  contrary,  in  virtue  of  the  exaltation  of  their  naturally 
positive  condition,  combine  with  the  negative  oxygen  most  readily,  on  the 
principle  that  bodies  in  the  opposite  electrical  condition  attract  each  other. 
The  positive  metal,  therefore,  oxydizes  most  speedily,  while  the  negative 
metal  remains  uninjured. 

What  is  called  galvanized  iron,  is  iron  covered  entirely,  or  in  part,  with  a 
coating  of  zinc.  The  galvanic  action  between  the  two  oxydizes  the  zinc, 
but  protects  the  iron  from  rust.  Sir  Humphrey  Davy  attempted  to  apply  this 
principle  to  the  protection  of  the  copper  sheathing  of  ships  (which  wastes 
rapidly  through  the  action  of  the  oxygen  in  sea-water),  by  placing  at  inter- 
vals over  the  copper  small  strips  of  zinc.  The  experiment  was  tried,  and  a 
piece  of  zinc  as  large  as  a  pea  was  found  adequate  to  preserve  forty  or  fifty 
square  inches  of  copper  ;  and  this  wherever  it  was  placed,  whether  at  the 
top,  bottom,  or  middle  of  the  sheet,  or  under  whatever  form  it  was  used. 
The  value  of  the  application  was,  however,  neutralized  by  a  consequence 
which  had  not  been  foreseen  ;  since  the  protected  copper  bottom  rapidly  ac- 
quired a  coating  of  sea-weeds  and  shell-fish,  whose  friction  on  the  water 
became  a  serious  resistance  to  the  motion  of  the  vessel.  The  adhesion  of 
these,  under  ordinary  circumstances,  is  prevented  by  the  corrosion  of  the 
copper  by  oxygen,  and  by  the  poisonous  action  of  the  compounds  of  copper 
and  oxygen  which  are  thereby  formed. 

The  principle,  however,  has  been  applied  with  success  for  the  protection 
of  iron  pans  used  in  evaporating  sea-  water,  and  in  other  similar  apparatus. 


.—  Ho-w  is  this  action  accounted  for?     What  is  galvanized  iron?     What 
practical  application  of  this  principle  was  attempted  by  Sir  Humphrey  Davy  ? 


'* 


INORGANIC  CHEMISTRY. 


/  THAT  department  of  Chemistry  which  treats  of  inor- 
ganic, or  unorganized  bodies,  is  termed  Inorganic  Chem- 
istry. 

It  includes  the  doctrines  of  affinity,  the  laws  of  combi- 
nation, the  chemical  history  of  the  elementary  bodies,  and 
of  those  compounds  of  the  elements  which  are  not  the  pro- 
duct, either  directly  or  indirectly,  of  living,  organized  bodies. 


CHAPTER    Y. 

THE  GENERAL  PRINCIPLES  OF  CHEMICAL  PHILOSOPHY. 

250.  Elements. — A  chemical  element  is  a  material  sub- 
stance not  yet  analyzed  or  taken  apart — not  yet  resolved 
by  any  process  into  two  or  more  bodies  differing  from 
itself. 

No  one  substance  within  the  reach  of  man  is,  however,  positively  known  to 
be  elementary ;  and  the  student  should  distinctly  understand,  that  it  can  not 
rightly  be  inferred,  because  a  body  has  not  yet  by  any  known  process  been 
decomposed,  that  it  never  will  be. 

251.  NnjnJierof  the  Elements, — The  number  of  elements 
at  present/uHy  recognized  by  chemists  is  sixty-two.     Of 
these  only  twenty-nine  were  known  at' the  commencement 
of  the  present  century.* 

*  This  fact  will  illustrate  to  the  general  student  one  great  feature  in  the  progress  of 
modern  chemistry;  but  to  the  chemist,  the  discovery  of  thirty-three  new  elementary 


QUESTIONS.— What  is  inorganic  chemistry  ?    What  is  a  chemical  element  ?    Is  any  sub- 
stance positively  known  to  be  elementary  ?    What  is  the  number  of  the  elements  ! 


PRINCIPLES    OF    CHEMICAL    PHILOSOPHY.      157 

252,  Classification  of  the  Elements, — The  elements  are 
usually  divided  into  two  great  classes,  the  metallic  and 
non-metallic  substances,  or  the  Metals  and  the  Metalloids. 
The  substances  comprised  in  the  first  class  are  the  more 
numerous,  but  those  in  the  latter  are  the  more  abundantly 
distributed.* 

Of  the  sixty-two  elements,  five  are  gases,  viz.,  oxygen,  hydrogen,  nitrogen, 
chlorine,  and  fluorine  ;  two  are  simple  liquids,  mercury  and  bromine ;  the  re- 
maitider  are  solids,  at  common  temperatures.  Only  fourteen  of  the  elements 
are  olNcommon  occurrence,  and  of  these  the  great  mass  of  the  earth,  with  its 
atmosphere  and  water,  are  composed.  The  remainder  occur  only  in  com- 
paratively small  quantities,  and  fully  one  third  of  the  whole  number  are  so 
rare  as  not  to  admit  of  any  useful  application. 

A  very  few  only  of  the  elements  are  found  naturally  in  a  free  or  tincom- 
bined  state ;  of  such  we  may  mention  oxygen  and  nitrogen,  existing  in  the 
atmosphere ;  sulphur,  carbon,  and  a  few  of  the  metals,  as  gold,  platinum, 
copper,  etc.,  distributed  throughout  the  earth.  The  majority  exist  only  in 


bodies  implies  an  amount  of  laborious  and  protracted  research,  preceding  and  following 
each  discovery,  of  which  words  can  convey  to  the  uninitiated  no  adequate  idea. 

*  The  alchemists  regarded  the  metals,  the  only  elementary  bodies  with  which  they  were 
acquainted,  as  compound  substances.  The  baser  metals,  as  lead,  iron,  copper,  etc.,  they 
believed  to  contain  the  same  elements  as  gold,  from  which  they  differed  on  account  of 
their  association  with  impurities  ;  these  impurities  being  separated,  it  was  imagined  that 
^old  would  remain. 

The  problem,  known  as  the  "  transmutation  of  metals,"  which  they  sought  to  solve,  and 
labored  for  centuries  to  effect,  was  not  to  generate  or  create  metals,  but  to  change  the 
proportion  of  the  elementary  substances  which  composed  them.  "For  a  century  or 
more,"  says  Professor  Faraday,  in  a  recent  lecture,  "  it  has  been  the  custom  to  spurn  the 
doctrines  of  the  alchemists  as  devoid  even  of  the  semblance  of  philosophic  truth,  The 
time  has,  however,  past  for  this  opinion  to  be  maintained,  and  within  the  last  few  years  a 
series  of  manifestations  have  been  noticed  which  go  far  to  vindicate  many  of  their  opinions." 
At  a  meeting  of  the  British  Association  for  the  PromotioiPof  Science  in  1851,  M.  Dumas 
and  Professor  Faraday  both  avowed  their  belief  in  the  possibility  of  transmutation,  and 
the  latter  stated  that  he  had  even  experimented  with  a  view  of  producing  this  result, 
and  should  continue  to  do  so.  It  is  not,  however,  to  be  understood  that  chemists  ex- 
pect transmutation  will  be  effected  in  exactly  the  sense  of  the  old  alchemical  philosophy. 
There  is  no  evidence  that  lead  can  be  converted  into  silver,  or  copper  into  gold.  M.  Du- 
mas suggests  that  the  first  successful  transmutation  as  regards  metals  will  be  to  effect  a 
change  of  physical  state  merely,  without  touching  chemical  composition  ;  thus,  already 
we  have  carbon,  which,  as  the  diamond  and  as  charcoal,  manifests  two  widely  different 
states.  Sulphur  also  assumes  two  forms,  as  also  phosphorus,  silicon,  and  boron.  Then 
why  not  a  metal  ? 

Within  a  very  recent  period  (185T),  a  series  of  experiments  have  been  published  by  Dr. 
Draper  of  New  York,  which  seem  to  indicate  that  silver  is  capable  of  transmutation  into 
another  metal,  possessing  somo  of  the  properties  and  characteristics  of  gold.  "  It  is  hard 


QUESTIONS.  —Into  what  two  great  classes  are  the  elements  usually  divided  ?  How  many 
of  the  elements  are  gaseous  ?  How  many  liquid  ?  How  are  the  elements  distribnted  in 
nature  ?  In  what  condition  are  they  generally  found  f 


158  INORGANIC     CHEMISTRY. 

combination  with  each  other,  and  in  this  condition  they  are  so  completely  dis- 
guised as  to  manifest  few  or  none  of  their  characteristic  properties. 

253.  Compound  Bodies, — All  compound  bodies  are  formed 
by  the  chemical  union  of  two  or  more  of  the  elementary 
substances. 

The  compounds  so  resulting  are,  as  might  be  supposed,  almost  innumer- 
able, and  the  progress  of  research,  is  continually  adding  to  their  number. 
Many  of  the  compounds  artificially  formed  by  chemical  action  have  no  ex^t- 
ence  in  nature.  Some  of  them  are  of  eminent  utility  to  man,  while  others 
possess  properties  of  a  strange  and  fearful  character.  Happily,  however,  the 
majority  of  those  compounds  which  are  especially  deleterious  are,  by  the  dif- 
ficulty and  expense  of  their  preparation,  placed  far  beyond  the  reach  of  the 
majority  of  mankind. 

254.  Cause  of  Chemical  Combination . — In  the  early  days 
of  chemistry,  chemical  combination  between  different  substances  was  supposed 
to  take  place  through  the  agency  and  guidance  of  some  spiritual  or  super- 
natural power  which  invested,  or  dwelt  in  every  form  of  matter,  both  ani- 
mate and  inanimate.  The  popular  names  of  many  chemical  substances  at  the 
present  time,  such  as  spirit  of  wine,  spirit  of  nitre,  etc.,  are  evidences  of  the 
former  general  credence  in  this  doctrine.  Stahl,  a  noted  chemist  who  died  in 
1685,  taught  that  chemical  combination  proceeded  from  an  approximation  of 
the  combining  parts,  somewhat  after  the  manner  of  wedges.  Modern  chem- 
istry explains  chemical  combination  between  different  substances,  as  occur- 
ring through  the  agency  of  an  attractive  farce,  acting  only  between  the  atoms, 
or  molecules  of  dissimilar  substances,  and  only  at  insensible  distances.  This 
force,  to  distinguish  it  from  other  forms  of  attraction,  is  termed  affinity.  To 

to  think,"  says  Sir  David  Brewster,  "  that  the  so-called  elements  are  truly  simple.  The 
instinct  of  humanity  revolts  against  believing  that  the  Maker  has  departed  from  his 
wonted  simplicity  of  procedure  in  this  one  part  of  creation,  and  flung  such  a  number  of 
unchangeable  elements  from  his  immediate  hand.  Many  thoughtful  and  ingenuous  men, 
indeed,  have  frankly  supposed  that  it  were  more  like  the  nature  of  Deity,  as  shown  by 
his  interpreted  works,  to  pour  forth  the  unreckonable  variety  of  things  from  the  bosom 
of  one  or  two  principles.  Thales  and  the  Greek  physicists,  Roger  Bacon,  Stahl,  Lavoi- 
sier, Sir  H.  Davy,  and  Berzelius,  have  all  given  more  or  less  expression  to  this  idea.  The 
greatest  question  in  chemistry,  or  in  plain  earnest,  the  one  question  of  the  age  then,  is 
precisely  this: — What  is  the  interior  nature  of  these  elements  ?  Science  bids  us  ask,  and 
perhaps  nature  is  ready  to  answer  it ;  but  what  shall  be  done,  since  no  analytical  power 
can  move  one  of  those  steadfast  natures  from  its  propriety?  Let  synthesis  be  tried  if 
analysis  has  failed ;  synthesis  has  never  been  tried.  It  is  in  the  highest  degree  probablo 
that  all  the  present  elements  are  equi-distant  from  simplicity,  and  all  equally  compound, 
if  there  be  any  truth  in  the  unanimous  testimony  of  chemical  analogy.  Their  case  is  ex- 
actly like  that  of  potassa,  soda,  lime,  and  their  congeners,  before  the  discovery  of  potas- 
sium ;— that  is  to  say,  potassa  once  discovered  to  be  metallic  oxyd,  all  the  rest  were  clearly 
metallic  oxyds  too,  as  experiment  was  not  long  of  showing.  In  the  same  way,  if  the  secret 
of  one  of  these  silent,  tantalizing  elements  be  discovered,  the  secret  of  them  all  is  out." 

QUESTIONS. — How  are  compound  bodies  formed  ?  Do  all  the  compounds  known  to  the 
chemist  exist  in  nature  ?  How  did  the  early  chemists  explain  chemical  combination  ? 
How  does  modern  chemistry  explain  it? 


PEINCIPLES    OF    CHEMICAL     PHILOSOPHY.      159 

the  question  "  What  is  the  attractive  force  thus  designated  ?"  no  satisfactory 
answer  can  be  given.  There  are,  however,  some  reasons  for  supposing  it  to 
be  a  modification  of  electrical  force. 

-1^255.  Characters  of  Chemical  Affinity,— Chemical  af- 
finity is  Hlitmguished  from  all  other  kinds  of  attractive 
forces  which  act  at  minute  distances,  by  certain  peculiar 
characteristics.  These  are  briefly  as  follows  : — • 

I.  It  is  exerted  within  its  own  limits  with  intense  en- 
ergy, but  beyond  those  limits  it  is  entirely  powerless. 

An  iron  wire  which  will  support  a  weight  of  a  thousand  pounds  without 
breaking,  will  in  a  few  minutes  yield  to  the  almost  noiseless  action  of  a  mix- 
ture of  sulphuric  acid  and  water.  The  tenacious  metal  will  dissolve — particle 
by  particle  will  be  detached  from  the  iron — and  in  the  clear  liquid  which  re- 
sults, no  vestige  of  the  structure  of  the  metal  will  remain.  It  is  rarely  possi- 
ble by  minute  subdivision  to  cause  the  particles  of  different  substances  to 
approximate  sufficiency  near  to  produce  chemical  action.  Tartaric  acid  and 
carbonate  of  soda  may  be  incorporated  by  grinding  for  hours  in  a  mortar, 
but  they  will  not  act  chemically  upon  each  other.  If,  however,  we  add  a 
portion  of  water,  which  dissolves  the  particles  of  both  and  allows  them  mu- 
tually to  approach  closer,  a  chemical  union,  accompanied  by  an  effervescence, 
immediately  takes  place. 

The  amount  of  power  or  work  produced  by  the  action  of  chemical  affinity 
is  in  general  very  great,  and  in  some  instances  we  may  approximately  meas- 
ure and  compare  it  with  other  forces.  For  example,  coal  burns  and  produces 
heat  solely  in  consequence  of  the  affinity,  or  attractive  force,  which  causes 
particles  of  oxygen  in  the  air  to  unite  with  particles  of  coal.  Now,  a  pound 
of  the  purest  coal,  burned  under  the  proper  circumstances,  and  its  resulting 
heat  applied  to  the  production  of  steam,  will  generate  a  power  capable  of 
lifting  a  weight  of  100  pounds  to  a  height  of  20  miles,  or  1  pound  2,000  miles. 
This  result,  therefore,  is  a  measure  of  the  chemical  force  of  affinity  which 
operates  between  the  particles  of  a  pound  of  coal  and  the  quantity  of  oxygen 
that  unites  with  them. 

II.  It  is  only  exerted  between  dissimilar  substances. 

No  manifestations  of  this  force  can  take  place  between  two  pieces  of  iron, 
two  pieces  of  copper,  or  two  pieces  of  sulphur ;  but  between  sulphur  and 
copper,  or  sulphur  and  iron,  chemical  action  of  the  most  energetic  kind  may 
occur. 

Were  there  but  one  kind  of  matter  in  the  universe,  the  force  of  affinity 
could  not  exist ;  no  chemical  action  could  take  place,  and  the  science  of 
^chemistry  would  be  unknown. 

QUESTIONS. — What  do  we  know  of  the  nature  of  affinity  ?  State  and  illustrate  the  first 
characteristic  of  affinity  ?  What  is  said  of  the  amount  of  work,  or  power  which  chemical 
affinity  is  capable  of  producing?  Give  an  illustration.  State  and  illustrate  the  second 
characteristic  of  affinity. 


160  INORGANIC     CHEMISTRY. 

III.  Generally  speaking,  the  greater  the  difference  in 
the  properties  of  bodies,  the  greater  is  their  tendency  to 
enter  into  chemical  combination.     Between  bodies  of  a 
similar  character,  the  tendency  to  union  is  feeble. 

IV.  Chemical  affinity  occasions  an  entire  change  in  the 
properties  of  the  substances  acted  upon, 

This  change  is  most  remarkable,  and  is  of  such  a  character  as  could  not 
be  predicted  from  any  acquaintance  with  the  substances  in  a  separate  condi- 
tion. Thus",  if  we  dissolve  copper  in  sulphuric  acid,  we  obtain  a  blue,  semi- 
transparent  substance ;  while  iron  treated  in  the  same  manner,  yields  a  light 
green  product. 

Although  in  a  combination,  the  properties  of  the  constituents  are  changed, 
and,  as  far  as  ordinary  observation  is  concerned,  are  destroyed,  yet  they  really 
exist  in  the  compound,  and  can  be  again  reproduced  by  restoring  the  com- 
bining elements  to  their  original  condition. 

V.  The  power  of  affinity  is  exerted  between  different 
kinds  of  matter  with  different,  but  definite   degrees  of 
force. 

Nitric  acid,  for  example,  will  combine  with  and  dissolve  most  of  the  metals, 
as  silver,  mercury,  copper,  and  lead ;  but  it  unites  with  them  with  very  dif- 
ferent degrees  of  intensity.  With  silver  the  combination  is  less  powerful  than 
with  mercury,  less  so  with  mercury  than  with  copper,  and  with  copper  less 
again  than  with  lead.*  Indeed,  the  different  elements  may  be  arranged  in 
tables,  in  such  a  way  as  to  indicate  by  their  order  the  degree  of  affinity  which 
they  respectively  have  for  some  particular  element. 


*  The  difference  in  the  strength  of  the  affinity  exist- 

FIG.  74.  ing  between  different  Substances  may  be  easily  illus- 

trated by  the  following  experiment :— Dissolve  a  few 
crystals  of  acetate  of  lead  (sugar  of  lead)  in  a  small 
quantity  of  water,  and  fill  a  phial  with  the  solution.  If 
a  piece  of  zinc  be  now  suspended  In  the  liquid,  It  will* 
after  a  little  time,  become  covered  With  a  gray  coating, 
from  which  brilliant  metallic  epangles  Will  gradually 
shoot  forth  (see  Fig.  74)  somewhat  in  the  shape  of  a 
tree.  These  are  pure  lead,  and  the  phenomenon  is  fa- 
miliarly known  as  the  lead  tree.  The  effect  thus  pro- 
duced is  due  to  the  superior  affinity  of  the  zinc  for  the 
acetic  add  combined  with  the  lead,  which  cau«es  the 
two  metals  to  interchange  places—?,  e.,  the  zinc  combin- 
ing with  the  acid  and  entering  into  solution,  and  the  lead 
being  deposited  in  a  metallic  state,  in  place  of  the  zinc. 
If  the  action  be  kept  up  sufficiently  long,  every  particle  of  lead  may  be  in  this  way  with- 
drawn from  the  liquid. 


QTTESTIONB.— What  is  the  third  characteristic  of  affinity  ?    What  is  the  fourth  ?    Illus- 
trate this.    Is  the  force  of  affinity  always  uniform  ?    How  may  this  be  shown  ? 


PKINCIPLES    OF    CHEMICAL    PHILOSOPHY.      161 

VI.  However  much  the  properties  and  form  of  bodies 
may  be  changed  by  the  action  of  chemical  affinity,  no  de- 
struction of  matter  ever  ensues — the  weight  of  the  pro- 
ducts of  combination  being  always  exactly  equal  to  that 
of  the  component  elements  before  combination. 

By  means  of  a  simple  experiment  it  may  be  shown  that  even  although  a 
substance  may,  through  the  action  of  chemical  affinity,  vanish  from  our  sight, 
it  still  continues  to  exist  as  a  gas  which  has  the  same  weight  as  the  visible 
solid  which  furnished  it.  Into  a  glass  flask,  A,  Fig.  75,  of  about  250  cubic 
inches  capacity,  which  is  provided  with  a  brass  cap  and  stop-cock,  10  or  12 
grains  of  gun-cotton  are  introduced.  The  air  in  the  flask  is  then  completely 
exhausted  by  means  of  an  air-pump,  and  the  flask  weighed.  The  cotton  is 
then  ignited  by  means  of  two  wires,  a  and  b,  proceeding  from  a  galvanic  bat- 
tery, and  passing  through  the  cap  of  the  flask. 
On  the  transmission  of  a  voltaic  current,  the 
cotton  entirely  disappears  with  a  brilliant 
flash,  but  the  flask,  if  weighed  again,  will  be 
found  to  be  as  heavy  as  before  the  cotton  was 
fired. 

VII.  Chemical  combination  of 
substances   may   either   occur   in- 
stantly on  mixture,  or  may  be  in- 
definitely   postponed   until    some 
other  force,  as  heat,  for  example, 
produces  a  commencement  of  tbe 
action. 

In  a  large  proportion  of  cases,  chemical  ac- 
tion will  not  commence  spontaneously.  A  heap  of  charcoal  will  remain  un- 
altered in  the  air  for  years ;  but  if  a  few  pieces  be  made  red  hot  and  then 
thrown  upon  the  heap,  chemical  combination  between  the  charcoal  and  the 
oxygen  of  the  air  is  commenced  by  the  heat,  and  continues  until  the  whole 
mass  is  burned.  In  other  instances  chemical  action  commences  without  the 
application  of  any  extraneous  force.  Phosphorus  begins  to  burn  slowly  the 
instant  it  comes  in  contact  with  the  atmosphere,  and  exposed  to  the  heat  of 
the  sun,  speedily  bursts  into  a  flame. 

Ca-tal'y-sis ,— The  mere  presence  of  a  third  lody  will 
sometimes  awaken  or  excite  the  force  of  affinity  between 


QTTESTIONS — la  matter  in  its  changes  consequent  on  the  action  of  affinity  ever  de- 
stroyed ?  What  experiment  illustrates  this  ?  Under  what  varying  circumstances  will 
chemical  combination  take  place?  Will  chemical  action  between  different  substances 
generally  commence  spontaneously?  Illustrate  this.  What  is  catalysis ? 


162  INORGANIC    CHEMISTRY. 

two  other  bodies  to  an  extent  sufficient  to  cause  their 
union — without  itself  undergoing  any  alteration,  either 
mechanical  or  chemical.  Such  an  action  is  termed  Ca- 
talysis. It  is  also  sometimes  called  the  action  of  pres- 
ence. 

Phenomena  of  this  character  are  the  most  curious,  and,  in  some  respects, 
the  most  difficult  of  explanation  of  any  in  chemistry.  A  familiar  example  of 
this  action  is  afforded  us  in  the  case  of  yeast,  a  most  minute  particle  of  which 
is  able  to  excite  fermentation  in  a  large  quantity  of  sugar  in  solution.  Other 
examples  will  be  noticed  in  the  progress  of  this  work. 

JVascent  State  . — Chemists  have  long  recognized  the  fact,  that  bodies, 
when  in  the  act  of  liberation,  or  separation  from  other  substances,  display 
far  more  energetic  affinities  than  under  ordinary  circumstances.  This  con- 
dition is  termed  the  nascent  (from  the  Latin  nascor,  to  be  born,)  state. 
Thus,  hydrogen  and  nitrogen  gases,  under  ordinary  circumstances,  do  not 
unite  if  mingled  in  the  same  vessel ;  but  when  these  two  gases  are  set  free 
at  the  same  time  from  the  decomposition  of  some  substance,  they  readily 
combine. 

VIII.  Chemical  compounds  may  be  formed  either  by  the 
direct  union  of  their  ingredients,  or  by  the  displacement 
of  one  substance  by  a  different  one  in  a  compound  pre- 
viously formed. 

IX.  Whenever  the  elements  unite  directly  with  each 
other,  heat  is  generally  evolved,  and  in  many  instances, 
light  also  ;  the  amount  of  each  being  proportioned  to  the 
rapidity  of  the  action. 

256.  Laws  of  Chemical  Combinations , — It  might  naturally 
be  supposed  that  chemical  combination  between  the  various  elementary  sub- 
stances would  take  place  in  all  proportions  indifferently,  in  the  same  manner 
as  unlike  particles  of  matter  can  be  mingled  together  mechanically.  Such, 
however,  is  not  the  case,  but  the  relative  proportions  in  which  different  ele- 
ments unite  is  determined  by  fixed  laws.* 


*  It  should  be  here  remarked,  that  the  views  adopted  in  this  work  are  those  of  Ber- 
zelius,  Mitscherlich,  Dumas,  Hayes,  and  most  of  the  leading  chemists  of  the  day — viz. 
that  all  mixtures  of  gases  with  gases,  liquids  with  liquids,  and  all  solutions  proper,  of 
solids  in  liquids,  are  not  chemical  combinations,  unless  they  take  place  in  definite  propor- 
tions. Apparent  combination  in  indefinite  proportions,  as  of  alcohol  with  water,  may  bfl 

QUESTIONS.— What  is  understood  by  the  nascent  state?  In  what  two  ways  may 
chemical  compounds  be  formed  ?  What  phenomena  of  heat  and  light  attend  chemical 
combinations?  Do  substances  enter  into  combination  in  all  proportions?  Enumerate 
the  laws  which  regulate  chcminal  combination. 


PRINCIPLES    OF    CHEMICAL    PHILOSOPHY.      163 

These  laws,  which  are  three  in  number,  regulate  the  mode  of  combination 
of  every  known  chemical  compound,  and  are  usually  called  the  Law  of 
Definite  Proportions,  the  Law  of  Multiple  Proportions,  and  the  Law  of  Equiv- 
alent Proportions. 

257.  Law  of  Definite  Proportions,— In  every  chemical 
compound  the  nature  and   proportion  of  its  constituent 
elements  are  fixed,  definite  and  invariable. 

For  instance,  100  parts  of  water  contain  8 8 -8 9  of  oxygen  and  11 '11  hydro- 
gen. It  matters  not  in  what  condition  the  water  may  exist — in  springs,  or 
in  the  ocean,  in  the  form  of  ice,  dew,  cloud,  or  steam,  its  composition  is  uni- 
form and  certain.  "When  artificially  prepared,  by  causing  the  gas  hydrogen 
to  unite  chemically  with  the  gas  oxygen,  the  same  proportions  are  required, 
that  is,  11 '11  grains,  ounces,  or  pounds  of  hydrogen  must  be  taken  for  every 
88-89  grains,  ounces,  or  pounds  of  oxygen.  If  either  one  of  the  constituents 
be  in  excess,  combination  will  still  take  place,  but  the  excess  will  be  rejected. 
So  also  in  the  case  of  other  simple  compounds.  A  piece  of  flint,  or  of  clear 
quartz  crystal,  come  from  whatever  source  it  may,  yields  in  every  100  parts, 
48 -2  of  the  element  silicon,  and  51 '8  of  oxygen. 

The  law  of  definite  proportions  may  be  proved  in  two  ways:  first,  by 
analysis,  that  is,  by  taking  the  compound  apart  and  comparing  the  products 
of  decomposition ;  and,  secondly,  by  synthesis,  that  is,  by  uniting  the  elements 
in  definite  proportions  to  form  the  required  compound. 

Although  of  great  simplicity,  it  constitutes  one  of  the  fundamental  princi- 
ples upon  which  modern  chemistry,  as  an  exact  science,  rests.  It  enters  into, 
all  the  practical  applications  of  chemistry  to  the  arts,  and  is  relied  upon  by 
the  analyist  as  a  means  of  verifying  and  classifying  his  results.  It  also  en- 
ables us  to  draw  a  broad  and  clear  distinction  between  a  mechanical  mixture 
and  a  chemical  combination ;  between  the  force  of  affinity  and  the  force  of 
adhesion,  which  produces  the  solution  of  solids  in  liquids. 

258.  Law   of  Multiple   Proportions , — It  frequently  happens 
that  one  elementary  substance  will  unite  with  another  in  more  than  one  pro- 
portion.    The  compounds  so  obtained  differ  greatly  in  their  properties,  but 
still  preserve  a  simple  relation  to  each  other.    The  law  which  governs  these 
relations,  and  which  is  known  as  the  law  of  multiple  proportions,  may  be 
stated  as  follows : — 

If  the  elements  A  and  B  unite  together  in  more  pro- 
portions than  one,  the  several  quantities  of  B,  which  unite 


explained  by  supposing:  that  definite  combination  takes  place  between  limited  quantities 
of  the  combining  substances,  in  the  first  instance,  and  that  the  compound  thus  formed  is 
afterward  mechanically  mixed  with  the  excess  of  either  of  the  constituents. 


QUESTIONS.— State  the  law  of  definite  proportions.  What  are  illustrations  ?  How  may 
this  law  be  proved?  What  is  its  practical  value  ?  "What  is  the  law  of  multiple  propor- 
tions? 


164  INORGANIC    CHEMISTRY. 

with,  the  same  quantity  of  A;  will  bear  a  very  simple  rela- 
tion to  each  other. 

Thus  we  may  have  a  series  of  compounds  like  the  following: — A-f-B ; 
A-f-2  B;  A-j-3  B;  A-j-4  B;  A+5  B,  etc.,  in  which  one  part  of  the  element  A 
unites  respectively  with  one,  two,  three,  four  and  five  parts  of  B,  to  form 
five  different  compounds,  each  possessing  different  properties.  Such  a  simple 
series  represents  the  five  different  compounds  which  nitrogen  forms  with 
oxygen — one,  two,  three,  four  and  five  parts  (by  weight)  of  oxygen  uniting 
with  one  part  of  nitrogen.  In  some  instances  the  relation  is  less  simple,  one 
or  two  proportions  of  one  element  combining  with  3,  5,  7,  etc.,  of  another — the 
law  simply  requiring  that  the  proportionals  shall  all  be  multiples  of  the  small- 
est. Thus,  compounds  represented  by  the  following  formulas  may  exist : — 

2  A-f3  B:  2  A-f-5  B;  2  A+7  B,  etc. 
In  this  1£  is  considered  as  the  smallest  combining  proportional  of  B. 

259.  Law  of  Equivalent  Proportions,— When  an  ele- 
mentary body  (A)  unites  with  other  bodies  (B,  C,  D,  etc.), 
the  proportions  in  which  B,  C  and  D  unite  with  A,  will 
represent  in  numbers  the  proportions  in  which  they  will 
unite  among  themselves,  in  case  such  union  takes  place  ; 
in  other  words,  the  fixed  proportions  in  which  the  ele- 
ments unite  among  themselves,  may  be  represented  nu- 
merically. 

Oxygen  is  an  element  that  forms  at  least  one  definite  compound  with  every 
other  elementary  substance,  with  a  single  exception.  United  with  hydrogen 
it  forms  water,  and  100  parts  of  water,  as  before  stated,  contain  88-S9  parts 
of  oxygen  and  11 '11  hydrogen.  United  with  the  element  calcium,  it  forms 
lime,  and  100  parts  of  pure  lime,  if  examined,  will  be  found  to  consist  of  28'58 
parts  of  oxygen  and  71-42  of  calcium.  In  like  manner  100  parts  of  potash 
contain  1I7'02  of  oxygen  and  82*98  of  the  element  potassium.  It  will  be 
apparent,  from  these  illustrations,  that  the  quantity  of  oxygen  is  not  the  same 
in  its  compounds  with  the  different  elements,  and  the  inquiry  next  arises, 
does  any  constant  relation  exist  between  the  proportions  of  oxygen  and  the 
proportions  of  the  different  elements  which  unite  with  it  to  form  compounds  ? 
The  existence  of  such  a  relation  may  be  shown  in  the  following  manner : — 
Having  ascertained  the  proportions  in  100  parts  of  the  various  compounds 
which  each  elementary  body  forms  when  it  combines  with  oxygen,  determine 
by  calculation  the  proportion  in  which  each  element  unites  with  the  same 
fixed  quantity  of  oxygen,  as  8  parts,  for  example.  A  series  of  proportional 
numbers  will  thus  be  obtained,  which  will  represent  the  ratios  in  which 


QUESTIONS. — Illustrate  the  law  of  multiple  proportions.     What  is  the  law  of  equiva- 
lent proportions  ?    How  is  the  law  of  equivalent  proportions  demonstrated  ? 


PRINCIPLES    OF    CHEMICAL    PHILOSOPHY.      165 

each  of  the  elements  combines  with  oxygen.  For  example,  in  the  case  of 
water,  it  will  be  seen  that  for  each  8  parts  of  oxygen,  1  part  of  hydrogen  is 
present. 

For  88-89  (the  quantity  of  oxygen  in  100  parts  of  water) :  11 -11  (the  quan- 
tity of  hydrogen) : :  8:1. 

So  also  in  lime,  for  each  8  parts  of  oxygen,  20  of  the  element  calcium  are 
present. 

For  28-58  :  71*42  : :  8  :  20. 

And  in  potash,  for  every  8  of  oxygen  there  are  39  of  potassium. 

For  17-02  :  82'96  : :  8  :  39. 

In  like  manner  it  has,  by  careful  and  laborious  investigation,  been  shown 
that  the  proportions  which  exist  between  oxygen  and  the  other  elements  in 
their  respective  combinations,  are  capable  of  being  represented  numerically. 
Thus,  8  parts  of  oxygen  unite  with  14  of  nitrogen,  16  of  sulphur,  6  of  carbon, 
28  of  iron,  32  of  copper,  100  of  mercury,  104  of  lead,  108  of  silver,  and 
so  on. 

But  further  experiments  have  led  to  the  very  remarkable  discovery,  that 
these  numbers  not  only  represent  the  quantities  of  the  different  elements  which 
unite  with  8  parts  of  oxygen,  but  they  also  indicate  the  simplest  proportions  in 
which  the  different  elements  can  unite  with  each  other. 

For  example,  not  only  does  1  part,  by  weight,  of  hydrogen,  16  of  sulphur, 
28  of  iron,  and  100  of  mercury,  severally  unite  with  8  parts  of  oxygen,  but  1 
part  of  hydrogen  unites  to  form  a  compound  with  16  parts  of  sulphur,  and  16 
of  sulphur  in  turn  unites  to  form  different  compounds  with  28  parts  of  iron  and 
100  of  mercury,  or  39  of  potassium. 

260.  Law  of  Substitution . — It  very  often  happens  also,  that  through 
the  varying  force  of  affiinity,  one  element  is  able  to  expel  and  replace  an- 
other hi  a  compound  previously  formed.  When  such  a  substitution  takes 
place,  it  always  happens  in  the  quantities  indicated  by  their  proportional 
numbers. 

This  principle  may  be  illustrated  as  follows  :• — In  mercantile  transactions, 
100  dollars  in  money  will  purchase  6  ounces  of  gold,  or  12  ounces  of  platinum, 
or  100  ounces  of  silver,  or  1,500  ounces  of  mercury;  consequently,  6  ounces  of 
gold  have  the  same  commercial  value  as  12  ounces  of  platinum,  or  100  ounces 
of  silver,  etc.  The  same  principle  holds  good  in  chemistry:  28  ounces,  or  28 
parts  of  any  other  denomination  by  weight,  of  iron,  100  of  mercury,  108  of 
silver,  or  one  of  hydrogen,  combine  with  8  of  oxygen.  Accordingly  28  ounces 
of  iron  have  same  chemical  value  as  100  ounces  of  mercury,  108  of  silver,  or 
1  ounce  of  hydrogen. — STOCKHARDT. 

261,  Chemical  EquivalentsTt-The  proportions,  or 
quantities  by  weight,  in  which  different  substances  unite 

QTJESTIONS.— What  remarkable  fact  has  been  ascertained  respecting  the  proportion  of 
the  elements  which  combine  with  oxygen  ?  What  are  examples  ?  What  is  understood 
by  the  law  of  substitutions ?  How  is  this  illustrated?  What  is  the  meaning  of  chemical 
equivalents  fr 


166  INORGANIC     CHEMISTRY. 

to  form  definite  chemical  compounds,  are  called  Chemical 
Equivalents  (from  cequus,  equal,  and  valor,  value).  They 
are  also  sometimes  designated  as  combining,  or  equivalent 
weights.  The  numbers  representing  or  expressing  these 
proportions  are  termed  equivalent  numbers. 

Thus,  by  1  equivalent  of  oxygen  is  to  be  understood  8  parts  of  it  by 
•weight;  by  1  equivalent  of  iron,  28  parts  by  weight;  by  1  equivalent  of  mer- 
cury, 100  parts  by  weight. 

It  will  be  readily  observed  that  the  numbers  used  to  designate  equivalents 
merely  express  the  relative  quantities  of  the  substances  they  represent ;  it  ia 
therefore  a  matter  of  little  consequence  what  numbers  are  employed  to  ex- 
press them,  provided  the  relations  between  them  are  strictly  observed.  Thus 
we  may  represent  the  equivalent  of  hydrogen  (which  is  the  smallest  of  all 
the  equivalent  numbers)  by  100,  or  1,000  as  well  as  by  1,  provided  all  the 
other  equivalent  numbers  are  multiplied  hi  an  equal  ratio ;  or  hydrogen  may 
be  represented  by  .01  or  .001,  if  all  the  other  numbers  are  equally  re- 
duced. If  hydrogen  were  represented  by  100,  oxygen  would  be  800,  and 
iron  2,800.  Or  if  hydrogen  were  O'Ol,  oxygen  would  be  0*08,  and  iron  0'28. 
It  is  the  ratio,  or  relative  proportion,  which  gives  value  to  these  numbers. 

In  England  and  the  United  States,  the  combining  number  of  hydrogen  is 
made  the  unit  of  comparison.  The  reason  why  this  element  is  selected  is  be- 
cause it  combines  with  oxygen  and  other  elements  hi  a  smaller  proportion  by 
weight  than  any  other  known  substance,  and  the  numbers  representing  the 
combining  proportions  of  all  the  other  elements,  may  also,  with  few  excep- 
tions, and  without  material  error,  be  taken  as  multiples  by  whole  numbers  of 
the  equivalent  of  hydrogen.  The  equivalent  number  of  hydrogen  in  this 
scale  is  1,  and  as  one  part  of  hydrogen  is  united  in  water  with  exactly  8 
parts  of  oxygen,  the  equivalent  number  for  oxygen  is  8. 

On  the  Continent  of  Europe,  most  chemists  make  oxygen  the  unit  of  com- 
parison, and  assume  its  equivalent  number  to  be  100 :  the  equivalent  number 
of  hydrogen  will  be,  therefore,  8  times  less,  or  12-5,  and  the  equivalent  num- 
bers of  the  other  elements,  calculated  according  to  the  hydrogen  scale,  will 
also  be  changed  proportionally. 

In  the  following  table  the  elementary  substances  are  arranged  alphabetically, 
with  the  symbols  used  by  chemists  to  designate  them  affixed  to  each.  The 
numbers  representing  their  equivalent  or  combining  proportions,  calculated 
according  to  the  hydrogen  scale,  are  placed  opposite  to  each  element.* 


*  The  numbers  on  the  hydrogen  scale  will  be  adopted  in  this  work,  and,  generally 
speaking,  fractional  quantities  will  be  omitted. 

QUESTIONS.— What  of  equivalent  numbers?  May  the  numbers  expressing  equivalents 
be  varied  and  changed  ?  On  what  principle  ?  What  is  the  unit  of  the  scale  adopted  in 
England  and  the  United  States  for  indicating  the  numerical  relations  of  the  equivalents  ? 
Why  is  hydrogen  adopted  ?  What  is  the  unit  adopted  upon  the  Continent  of  Europe  ? 


PRINCIPLES    OP    CHEMICAL    PHILOSOPHY.      167 

The  names  of  the  elements  which  from  their  rarity  may  be  regarded  as  un- 
important, are  given  in  Italics. 

TABLE   OF   THE   ELEMENTARY   SUBSTANCES,   WITH  THEIR  EQUIVALENTS  AND 

SYMBOLS. 


Name. 

Symbol. 

11=1. 

Name. 

Symbol. 

H—  1. 

Al 

13-7 

Mo 

46' 

Sb 

129- 

Nickel 

Ni 

29  -6 

As 

75* 

Nb 

Ba 

63-50 

Nitrogen  

N 

14' 

Bismuth       .           ... 

Bi 

•21  2- 

Os 

99*6 

B 

10-9 

Oxygen  

o 

8- 

Br 

80- 

Pd 

53  .3 

Cd 

5(5- 

Pelopium  

Pe 

Ca 

20- 

p 

39* 

Carbon  

c 

6- 

Platinum  

Pt 

98-7 

Ce 

47- 

Potassium  (Kalium)  .     .  . 

J£ 

39  -2 

Cl 

35-59 

52  -2 

Cr 

20-7 

Ruthenium  

Ru 

59-2 

Cobalt  

Co 

29-5 

Se 

40' 

Cu 

31-7 

Silicium    or  Silicon 

Si 

21-3 

Di'dtjmium  

D 

Silver  (Argentum)  

ACT 

108- 

E 

Na 

23- 

Fl 

19- 

Sr 

44. 

Q 

0*9 

g 

16- 

Au 

93. 

Ta 

92' 

Hydrogen  

H 

1- 

Tellurium  

Te 

64* 

lltneniuin  

11 

Tb 

Iodine       

I 

127' 

Th 

59  '6 

Ir 

99- 

Tin  (Stannum) 

Sn 

59- 

Fe 

28- 

Ti 

25- 

La 

36. 

W 

94- 

Pb 

10!  -5 

u 

60- 

Lithium  

Li 

6-9 

v 

68-6 

Magnesium  

Mg 

12-2 

Yttrium. 

Y 

32-2 

Mn 

27-6 

Zinc 

Zn 

32-5 

Mercury  

Kg 

lOO- 

Zr 

22-4 

Three  other  substances  discovered  within  the  last  few  years,  and  desig- 
nated as  Aridium,  Donarium,  and  Norium,  are  claimed  to  possess  an  ele- 
mentary character.  If  then-  existence  is  fully  established,  the  number  of  the 
elements  must  be  considered  as  sixty-five. 

The  law  of  equivalents  applies  to  compound  substances\ 
equally  with  the  elements — >the  equivalent  of  a  combining  j 
number  of  a  compound  being  always  the   sum   of  the 
equivalent  of  its  components. 

Thus,  since  water  is  composed  of  1  equivalent,  or  8  parts  of  oxygen,  and  1 
equivalent,  or  1  part  of  hydrogen,  its  combinining  proportion  or  equivalent  is 
9.  The  equivalent  of  sulphuric  acid  is  in  like  manner  40,  because  it  is  a  com- 
pound of  1  equivalent,  or  16  parts  of  sulphur,  and  3  equivalents  of  oxygen ; 
(3X8=24),  and  16+24—40.  The  equivalent  number  of  potassium  is  39, 


QUESTION. — Does  the  law  of  combination  by  fixed  equivalents  extend  to  union  of  com- 
pound substances?    Illustrate  this. 


168  INORGANIC     CHEMISTRY. 

and  as  this  element  combines  with  8  of  oxygen  to  form  potash,  the  equiva- 
lent of  the  latter  must  be  39-|-8=47.  Now,  when  these  compounds  unite, 
one  equivalent  of  the  one  combines  with  one,  two,  three,  or  more  equivalents 
of  the  other,  precisely  as  the  elementary  substances  do.  For  example,  water 
unites  with  potash  to  form  a  compound,  but  it  does  so  only  in  the  proportion 
of  9  to  47  ;  sulphuric  acid  also  unites  with  potash  to  form  a  compound  (sul- 
phate of  potash),  but  only  in  the  proportion  of  40  to  47. 

To  illustrate  the  advantage  in  practical  operations  of  employing  the  scale 
of  equivalents,  we  will  suppose  a  person  wishes  to  manufacture  sulphate  of 
potash,  which  is  one  of  the  ingredients  which  enter  into  the  composition  of 
alum.  Having  purchased  in  the  market  the  necessary  components  of  sulphate 
of  potash,  viz.,  sulphuric  acid  and  potash,  he  mixes  the  two  together,  accord- 
ing to  their  equivalents,  in  the  proportion  of  40  parts  (pounds,  ounces,  or 
tons)  of  sulphuric  acid  with  47  parts  of  potash.  The  result  is.  that  all  tho 
sulphuric  acid  unites  with  all  the  potash,  and  the  greatest  product  of  the  com- 
pound is  obtained.  If,  on  the  other  hand,  he  had  mixed  the  sulphuric,  acid 
and  the  potash  in  any  other  than  the  above,  or  some  multiple  of  the  above 
proportions,  there  would  have  been  an  excess  or  deficiency  of  one  of  the 
ingredients,  and  consequently  a  loss  of  material.  The  sulphate  of  potash 
formed  by  the  partial  combination  would  also  prove  to  be  an  imperfect  article, 
from  the  mechanical  mixture  of  the  excess  of  one  of  the  ingredients  through- 
out its  substance. 

Previous  to  the  discovery  of  this  law  of  equivalents,  at  about  the  com- 
mencement of  the  present  century,  it  could  only  be  ascertained  by  laborious 
trials,  how  much  of  one  chemical  substance  was  required  to  combine  with,  or 
replace  another.  It  is  now  only  necessary  to  refer  to  the  table  of  the  propor- 
tional, or  equivalent  numbers  to  ascertain  beforehand  the  quantity  to  be  em- 
ployed. 

'-262.  Equivalent  Volumes, — When  bodies  are  capable 
of  assuming  the  form  of  a  gas,  or  vapor,  and  in  this  con- 
dition act  chemically  upon  and  combine  with  each  other, 
a  very  simple  ratio  prevails  between  the  quantities  which 
enter  into  combination,  measured  merely  by  their  bulk  or 
volume. 

Thus,  one  volume  of  a  gas,  which  may  be  distinguished  as  A,  unites  with 
one,  two,  or  three  volumes  of  B,  or  two  of  A  may  unite  with  three  of  B. 

If  when  two  gases  capable  of  union  by  contact  are  brought  together,  the 
volume  of  one  is  greater  than  its  combining  proportion,  the  excess  remains 
uncombined. 

The  volume  of  two  gases,  after  combination,  is  often  less  than  the  sum  of 


QUESTIONS. — Show  in  what  manner  the  law  of  equivalents  is  practically  applied  in  chem- 
ical operations  ?  "What  is  understood  by  equivalent  volumes  ?  Does  the  volume  of  the 
gases  always  remain  the  same  after  combination  ? 


PRINCIPLES     OF    CHEMICAL    PHILOSOPHY.      169 

of  their  volumes  in  their  separate  state ;  or  in  other  words,  the  two  gases  or 
vapors,  by  the  act  of  union,  sometimes  experience  a  condensation. 

It  is,  however,  a  very  curious  fact,  that  when  such  a  diminution  of  the 
volume  occurs,  it  always  takes  place  in  a  simple  ratio  to  the  volume  of  one 
or  both  of  the  combining  gases.  Thus,  three  volumes  of  hydrogen  and  one 
of  nitrogen  unite  to  form  ammonia ;  but  when  the  union  takes  place,  the  four 
volumes  instantly  contract  to  two,  or  one  half  their  former  bulk.  The  weight, 
however,  of  the  ammonia  formed  is  equal  to  the  united  weight  of  the  hydro- 
gen and  nitrogen  that  have  entered  into  its  composition. 

263.  Atomic  Theory . — A  consideration  of  the  facts  set  forth,  nat- 
urally suggests"  the  inquiry, — Why  is  it  that  all  the  different  kinds  of  matter 
with  which  we  are  acquainted,  in  entering  into  chemical  combination  with 
each  other,- are  constrained  to  do  so  according  to  certain  fixed  weights  and 
volumes,  and  not  otherwise?  The  response  from,  every  thinking  mind  will 
unhesitatingly  be  that  the  phenomena  in  question  must  originate  in  accordance 
with  some  great  law  or  principle  in  nature,  so  extensive  and  general  in  its 
character  as  to  affect  all  matter.  Experiment  and  observation  do  not,  and 
probably  can  not,  enable  us  to  say  definitely  what  this  law  is ;  but  a  careful 
consideration  and  comparison  of  all  the  facts  in  the  case,  led  Dr.  John  Dalton, 
an  eminent  English  chemist,  about  the  year  1808,  to  propose  a  theory  which 
so  satisfactorily  explains  the  remarkable  circumstances  attending  chemical 
combination,  that  scientific  men  of  all  countries  receive  it  as  substantially 
trua  This  theory  is  known  as  the  "  Atomic  Theory,"  or  the  "  Theory  of 
Atoms." 

The  atomic  theory  supposes,  in  the  first  instance,  that 
all  matter  is  composed  of  ultimate  particles,  or  atoms, 
which  are  incapable  of  subdivision.  (See  §  4,  page  10.) 

A  belief  in  this  hypothesis  dates  back  to  a  very  remote  period.  It  was  a 
doctrine  taught  by  that  sect  of  the  Greek  philosophers  known  as  the  Epicu- 
reans, and  during  the  middle  ages  it  formed  a  part  of  certain  theological  dog- 
mas maintained  by  parties  in  the  church.  In  more  modern  times,  it  received 
the  sanction  of  many  men  of  high  scientific  attainment,  as  Newton,  Bacon, 
and  others.*  These  opinions  can  not,  however,  be  regarded  in  any  other 
light  than  as  mere  speculations,  and  it  was  not  until  laborious  study  and 


*  "It  seems  to  me,"  says  Sir  Isaac  Newton,  "that  in  the  beginning,  God  formed  mat- 
ter in  a  solid  mass  of  hard,  impenetrable  particles ;  and  that  these  primitive  particles 
being  solids,  are  incomparably  harder  than  any  porous  bodies  compounded  of  them  ;  so 
very  hard  as  never  to  wear  or  break  in  pieces,  no  ordinary  power  being  able  to  divide 
what  God  made  one  in  the  first  creation." 


QUESTIONS. — What  inquiry  naturally  arises  in  the  mind  from  a  consideration  of  the  facts 
Btated  ?  According  to  what  theory  is  chemical  combination  explained  ?  Who  proposed  this 
theory  ?  What  does  the  atomic  theory  suppose  in  the  first  instance  ?  Is  this  supposition  of 
recent  origin  ? 

8 


170  INORGANIC     CHEMISTRY. 

research  had  elevated  chemistry  to  the  rank  of  an  exact  science,  that  any 
rational  evidence  upon  the  subject  could  be  appealed  to. 

The  atomic  theory,  as  proposed  by  Dalton,  further 
supposes,  that  the  atoms  of  each  separate  elementary  sub- 
stance have  all  the  same  characteristic  form  and  weight, 
and  that  when  combination  between  two  different  ele- 
ments takes  place,  one  or  more  atoms  of  one  substance 
arrange  themselves  in  the  most  symmetrical  manner  pos- 
sible by  the  side  of  one  or  more  atoms  of  another  substance, 
and  thus  form  a  compound  atom. 

In  the  simplest  combination,  one  atom  of  one  substance  combines  with  ono 
atom  of  another,  but  in  other  instances  the  proportion  may,  be  as  1  to  2,  3,  4, 
and  5,  or  as  2  to  3,  5,  7,  etc.  One  atom  of  one  kind  can  not  combine  with 
one  half  an  atom  of  a  different  kind,  or  with  any  other  fractional  part  of  an 
atom,  for  the  reason  that  no  such  quantities  exist — the  atoms  being-  incapable 
of  division.  Hence  the  immutable  nature  of  all  compound  bodies  existing 
either  in  nature  or  art. 

Furthermore,  as  combination  of  different  substances  takes  place  atom  by 
atom,  and  as  the  atoms  of  each  substance  have  a  size  and  weight  peculiar  to 
themselves,  we  have  an  explanation  of  the  circumstance  that  the  chemical 
union  of  quantities  of  different  kinds  of  matter  only  occurs  in  unchanging  pro- 
portions by  weight  and  volume — for  what  is  true  of  all  the  atoms  of  a  mass, 
must  be  true  of  the  whole. 

Again,  a  compound  atom  formed  by  the  union  of  two  dissimilar  atoms, 
must,  in  uniting  with  other  bodies,  necessarily  obey  the  same  laws  of  com- 
bination as  the  elementary  atoms,  and  be  in  turn  incapable  of  division,  since 
the  very  act  of  division  would  be  its  destruction,  so  far  as  its  compound  char- 
acter is  concerned. 

A  strong  argument  in  favor  of  the  truth  of  the  atomic  theory  is,  that  no 
reasonable  explanation  of  the  facts  pointed  out  can  be  given  by  the  adoption 
of  any  other  theory.  If  matter  is  infinitely  divisible,  and  if  atoms  have  no 
real  existence,  then  there  is  no  reason  why  bodies  should  not  combine  in  all 
proportions.  One  grain,  ounce,  or  pound,  of  one  substance  ought  to  combine 
with  the  half,  quarter,  tenth,  hundredth,  and  every  other  proportion  of  a 
grain,  ounce,  or  pound,  of  some  other  substance,  so  as  to  form  an  infinite  num- 
ber of  compounds,  all  possessing  different  properties.  But  this,  as  has  been 
already  stated,  never  happens. 

Dr.  Dalton  was  also  the  first  who  conceived  clearly  the  idea,  that  from  the 

QUESTIONS. — What  does  the  atomic  theory  of  Dalton  further  suppose  ?  How  does  the 
immutable  character  of  chemical  compounds  necessarily  follow  from  the  admission  of 
these  views?  How  is  the  doctrine  of  equivalent  proportions  explained  by  the  atomic 
theory?  What  is  a  strong  argument  in  favor  of  the  atomic  theory?  Can  the  relative 
•weights  of  the  ultimate  atoms  be  inferred  from  the  relative  actual  weights  of  the  ele- 
ments? 


PRINCIPLES    OF    CHEMICAL    PHILOSOPHY.      171 

relative  actual  weights  of  the  elements  which  make  up  the  mass  of  any  com- 
pound, the  relative  weights  of  the  ultimate  atoms  themselves  might  be  in- 
inferred,  and  represented  numerically.  The  method  of  reasoning  and  deduc- 
tion by  which  this  result  is  arrived  at  is  as  follows : — 

It  is  obvious  that  if  we  can,  by  any  method,  exactly  fix  the  relative  weights 
of  the  atoms  of  a  few  of  the  great  elementary  bodies,  oxygen,  hydrogen, 
nitrogen,  carbon,  etc.,  we  can,  by  an  extension  of  the-process,  solve  the  ques- 
tion for  all  other  simple  bodies,  and  for  the  most  complex  compounds  into 
which  they  enter.  Now,  to  attain  this  result,  it  is  necessary  to  take  one 
point  as  granted — the  truth  of  which,  although  not  susceptible  of  absolute  de- 
monstration, is  yet  rendered  probable  by  many  concurrent  facts.  This  once 
allowed,  the  process  becomes  one  of  simple  inductive  reasoning.  It  is 
assumed  that  when  two  elementary  substances  unite  in  several  proportions 
to  form  different  compounds,  that  the  combination  takes  place  in  the  first  or 
simplest  compound  in  the  proportion  of  one  atom  of  the  one  to  one  of  the 
other ;  in  the  second  compound,  of  one  atom  to  two  atoms ;  in  the  third,  of 
one  to  three,  and  so  on. 

Let  us  next  examine  the  practical  application  of  this  supposition.  "Water, 
composed  of  oxygen  and  hydrogen,  is  found  to  contain  these  ingredients  in 
the  proportion  of  8  to  1  by  weight.  Assuming,  which  many  reasons  make 
probable,  that  it  is  their  simplest  form  of  union,  viz.,  of  atom  to  atom,  we  ob- 
tain at  once  the  relative  weight  of  the  ultimate  atoms  of  oxygen  and  hydro- 
gen— as  8  and  1  respectively. 

Again,  we  have  a  series  of  five  chemical  compounds  of  oxygen  and  nitro- 
gen, in  which  the  proportion  of  oxygen  increases  uniformly  in  the  ratio  of  the 
simple  numbers,  so  that  nitric  acid,  the  fifth  in  order  of  these  compounds,  con- 
tains exactly  five  times  the  weight  of  that  which  exists  in  the  protoxide  of 
nitrogen,  the  first  of  the  series.  Concluding  that  the  latter  is  the  simplest 
form,  and  consists  of  a  single  atom  or  combining  proportion  of  each  of  its 
elements,  we  obtain,  by  analysis  of  this  gas,  the  relative  weights  of  8  and  14 
for  the  atoms  of  oxygen  and  nitrogen  composing  it.* 

Here  then  we  have  already  a  short  scale  of  proportions  fixed ;  in  which 
.hydrogen  is  the  unit,  oxygen  8,  and  nitrogen  14.  The  next  step,  in  complet- 
ing the  circle  of  combination,  furnishes  a  test  of  the  truth  of  these  results. 
Ammonia  is  a  compound  of  hydrogen  and  nitrogen ;  and  its  analysis,  exactly 


*  The  student  will  perhaps  he  able  to  obtain  a  clearer  idea  of  the  relation  of  -weights 
and  proportions  existing  in  the  five  compounds  of  oxygen  and  nitrogen  from  the  follow- 
ing table. 

RELATIVE  WEIGHTS.        RELATIVE  PROPORTIONS. 
Nitrogen.        Oxygen.  Nitrogen.      Oxygen. 

Protoxide  of  nitrogen, 14  8  1  1 

Binoxide  of  nitrogen, 14  16  1  2 

Hyponitrous  acid, 14  24  1  3 

Nitrous  acid, 14  32  1  4 

Nitric  acid,        14  40  1  6 

QUESTION . — How  is  this  conclusion  arrived  at  ? 


- 


172  INORGANIC    CHEMISTRY. 

made,  gives  proportions  of  the  two  which  involve  the  same  numbers  as  were 
obtained  by  the  preceding  methods. 

This  test  obviously  becomes  more  stringent  and  complete  as  we  extend  the 
number  of  bodies  thus  brought  into  conjunctions,  and  find  the  relative  weight, 
BO  determined  for  each,  strictly  maintained  in  all  their  forms  of  combination. 
The  atomic  weight  of  sulphur,  for  instance,  is  found,  by  analysis  of  its  com- 
pounds with  oxygen,  to  be  1 6.  Examining  its  simplest  form  of  union  with 
hydrogen,  in  sulphuretted  hydrogen,  the  proportion  is  found  to  be  exactly  16 
to  1,  or  one  atom  of  each,  thus  verifying  the  respective  numbers  before  ob- 
tained. In  a  like  manner  all  the  other  elementary  bodies  have  been  submit- 
ted, by  experiment,  to  the  same  law,  and  have  been  found  to  furnish  proofs 
precisely  similar  in  kind.  Thus  the  circle  of  demonstration  has  been  contin- 
ually enlarged ;  the  evidence  increasing  in  a  geometrical  ratio  with  the  num- 
ber of  objects  brought  within  the  scope  of  inquiry.  The  conclusion  is  as  cer- 
tain and  complete  as  any  one  of  pure  mathematics ;  or,  if  there  be  any  excep- 
tions, they  are  only  such  as  may  be  ascribed  to  imperfect  examination,  or 
some  other  cause  not  infringing  on  the  truth  of  the  fundamental  principle. 

From  what  has  been  stated,  it  follows  that  the  word 
atom  may  be  used  to  express  either  an  ultimate  individual 
particle  of  a  substance,  or  the  simplest  and  smallest  com- 
bining proportion  of  a  substance.  Indeed  it  is  customary 
in  chemical  works  to  employ  the  word  in  both  its  signifi- 
cations— atom  and  atomic  weights  expressing  the  same 
thing  as  equivalent  and  equivalent  weights. 

Many  other  curious  facts  and  relations  have  been  discovered  since  the  first 
announcement  by  Dalton  of  the  atomic  theory,  which  present  strong  addi- 
tional evidence  of  the  correctness  of  his  views. 

264.  Specific  Heat  of  Atom  s. — For  example,  there  appears  to  be 
a  relation  between  the  atomic  weight  of  a  body  and  its  capacity  for  heat. 
Thus,  the  atomic  weights  of  the  metals,  iron,  copper,  mercury,  and  lead,  are 
respectively  represented  by  the  numbers  28,  32,  100,  104.  Now  if  any  of 
these  four  metals  be  taken  in  these  relative  proportions,  it  will  require  the 
same  expenditure  of  heat  to  make  them  equally  hot.  104  pounds  of  lead  can 
be  heated  up  to  212°,  for  example,  by  burning  the  same  amount  of  alcohol 
which  will  heat  100  pounds  of  mercury,  32  of  copper,  or  28  of  iron.  A  simi- 
lar correspondence  is  also  known  to  exist  between  the  atomic  weights  and 
the  capacity  for  heat  of  tin,  zinc,  nickel,  cobalt,  gold,  platinum,  sulphur,  and 
tellurium,  and  according  to  some  authorities,  the  correspondence  extends  to 
all  the  elements.  If  this  last  supposition  is  true  (which  is  not  proved),  the 
determination  of  the  specific  heat  of  a  substance  would  also  afford  the  means 
of  knowing  its  atomic  weight  and  combining  equivalent.  Compound  atoms 

QUESTIONS.— Since  the  announcement  of  the  atomic  theory,  have  any  circumstances  con- 
firmatory of  its  correctness  heen  discovered  ?    la  there  a  relation  between  the  atomic 
of  an  element  and  its  capacity  for  heat  ? 


PRINCIPLES    OF    CHEMICAL    PHILOSOPHY.      173 

have  also,  in  some  instances,  been  proved  to  have  the  same  relations  to  heat 
as  the  simple  atoms  composing  them. 

There  has  also  an  interesting  relation  been  traced  between  the  atomic 
weights,  the  specific  gravities,  and  the  combining  measures  or  volumes  of 
those  elements  which  exist  in  the  gaseous  state,  or  are  capable  of  assuming 
it.  For  example,  a  cubic  foot  of  nitrogen  weighs  just  14  times  as  much  as 
a  cubic  foot  of  hydrogen  ;  a  cubic  foot  of  chlorine  35  times  as  much ;  of 
bromine,  80  times  as  much ;  of  oxygen,  16  times  a"s  much ;  and  the  same 
measure  of  the  vapor  of  iodine,  127  times  as  much.  Now,  these  numbers  re- 
spectively represent  the  density  or  specific  gravity  of  these  gases,  compared 
with  hydrogen  as  unity;  and  they  also  represent  the  atomic  weights,  or  com- 
bining equivalents,  of  these  several  elements, — with  the  exception  of  oxygen, 
which  is  double. 

It  is  important  for  the  student,  in  the  consideration  of  the  whole  subject, 
to  clearly  distinguish  between  the  doctrine  of  chemical  combination  by 
equivalents,  or,  as  it  is  often  termed,  "by  atomic  weight,"  arid  the  atomic 
theory.  The  first  is  a  truth  independent  of  all  theory,  and  rendered  manifest 
to  our  comprehension  by  experiment  and  practical  demonstration.  The 
atomic  constitution  of  matter,  on  which  the  law  of  combination  by  propor- 
tions is  supposed  to  depend,  can  not,  on  the  other  hand,  be  proved  by  ex- 
periment, and  still  remains,  and  probably  ever  must  remain,  in  the  condition 
of  a  highly  probable  theory.  The  most  subtile  and  refined  analysis  has  never 
yet  enabled  any  one  to  isolate  an  indivisible  portion  of  matter,  or  even  to 
adduce  any  direct  evidence  of  the  absolute  existence  of  matter  in  this  condi- 
tion.* 

•  Experimental  researches  have,  however,  in  some  instances  been  made  with  a  view  of 
obtaining  information  on  this  subject.  Dr.  Thompson,  of  England,  from  certain  assumed, 
but  probable  data,  estimated  an  atom  of  lead,  which,  according  to  the  table  of  equiva- 
lents, is  104  times  larger  than  an  atom  of  hydrogen,  as  only  1-31 0,000, 000,000th  of  a  grain. 
Ehrenberg,  the  eminent  microscopist,  has  proved  that  the  size  of  atoms,  if  they  exist, 
must  be  less  than  1-6,000,000  of  a  line  in  diameter,  a  line  being  assumed  as  l-12th  of  an 
inch.  More  recently,  Professor  Faraday  has  endeavored,  through  the  agency  of  light,  to 
obtain  some  evidence  of  the  existence  of  atoms.  (See  observations  on  divided  gold,  Lon- 
don Phil.  Mag.,  1856-57,  also  Annual  of  Scientific  Discovery,  1857-5S.)  The  only  posi- 
tive result  attained  to  was,  to  demonstrate  that  metallic  gold,  distributed  mechanically 
throughout  a  liquid  in  particles  so  minute  as  to  defy  detection  by  the  most  powerful  mi- 
croscope, still  retained  its  general  physical  properties. 

Concerning  the  form  of  atoms  two  views  are  entertained.  According  to  one  hypothesis, 
atoms  have  the  same  form  as  the  fragments  obtained  by  splitting  a  crystallized  body  in 
the  direction  of  its  lines  of  cleavage.  (See  p.  55,  §  73.)  Antimony,  which  may  be  cleft  in 
directions  parallel  to  the  faces  of  an  acute  rhombohedron,  is  resolved  by  this  mode  of  di- 
vision into  similar  rhombohedrons  of  continually  smaller  and  smaller  dimensions  ;  and  if 
we  conceive  the  cleavage  to  be  carried  to  the  utmost  possible  limit,  the  smallest  rhombo- 
hedrons thus  obtained  will  be  the  atoms  of  antimony.  Other  substances,  in  like  manner, 


QUESTIONS. — Is  there  any  relation  between  the  atomic  weight,  the  specific  gravity,  and 
combining  volume  of  certain  elements  ?  What  clear  distinction  should  be  made  between 
the  atomic  theory  and  the  law  of  equivalent  proportions  ? 


174  INORGANIC     CHEMISTRY. 

265.  Chemical  Nomenclature  and  Symbols, — Chemists 
recognize  three  great  classes  of  substances,  viz.,  Acids, 
Bases,  and  Salts. 

Acids, — The  common  idea  of  an  acid  is,  a  substance  so- 
luble in  water,  which  possesses  the  property  of  sourness, 
and  which  exerts  such  an  action  on  vegetable  blue  colors 
as  to  change  them  to  red.  The  chemist,  however,  disre- 
gards these  properties,  and  considers  all  those  substances 
to  be  acids  which  enter  into  combination  with  bases  to 
form  salts. 

Yinegar,  oil  of  vitriol  or  sulphuric  acid,  and  aquafortis  or  nitric  acid,  are  fa- 
miliar examples  of  the  class  of  acids. 

Bases, — A  substance  which  is  capable  of  entering  into 
combination  with  an  acid,  and  by  so  doing  destroys,  or 
neutralizes  its  properties,  is  called  a  Base.  The  bases  in- 
clude those  substances  known  as  the  alkalies,  beside  many 
other  bodies  of  entirely  different  character. 

Alkalies, — An  alkali  is  a  substance  possessing  many 
qualities  exactly  the  reverse  of  those  which  belong  to  an 
acid.  It  dissolves  in  water,  and  produces  a  liquid,  soapy 
to  the  touch.  It  has  an  acrid,  nauseous  taste,  and  restores 
the  blue  color  to  vegetable  extracts  which  have  been  pre- 
viously reddened  by  acid. 

Potash,  soda,  and  hartshorn  or  ammonia,  are  instances  of  well-known 
alkalies. 

Salts, — Any  compound  produced  by  the  union  of  an  acid 
and  a  base  is  termed  a  Salt. 

By  the  voltaic  pile,  salts  are  decomposed  into  acids  and  bases,  the  acids 
going  to  the  positive  pole,  and  the  bases  to  the  negative.  We,  therefore,  call 


admit  of  cleavage  into  cubes,  prisms,  etc.  This  view  of  the  form  of  atoms  offers  the 
easiest  explanation  of  the  regular  crystalline  form,  and  the  cleavage  of  simple  substances. 
The  second  hypothesis  supposes  that  atoms  have  a  spherical  form  ;  and  that  regular 
crystalline  forms  are  occasioned  by  the  peculiarity  of  their  arrangement  in  varying  num- 
bers and  angles.  Thus,  4  spheres  forming  a  base,  and  4  placed  perpendicularly  over 
them,  may  form  a  cube ;  2  or  4  layers  of  3  each  would  give  a  prism,  and  so  on. 

QUESTIONS. — What  three  great  classes  of  substances  are  recognized  by  chemists  ?  What 
is  an  acid  ?  What  are  examples  of  acids  ?  What  are  bases  ?  Define  an  alkali.  What 
are  examples  of  alkalies  ?  What  are  salts  ?  In  the  decomposition  of  a  salt  by  the  voltaio 
pile,  how  do  its  constituents  distribute  themselves  ? 


PRINCIPLES    OF    CHEMICAL   PHILOSOPHY.      175 

the  acid,  in  reference  to  its  electrical  character,  the  electronegative  constitu- 
ent of  a  salt,  and  the  base  the  electro-positive. 

Some  of  the  properties  of  acids  and  alkalies  may  be  experimentally  illus- 
trated by  means  of  a  colored  vegetable  solution,  such  as  the  purple  liquid 
prepared  by  slicing  a  red  cabbage  and  boiling  it  in  water.  If  a  quantity  of 
this  infusion  be  divided  into  two  portions,  and  to  the  one  be  added  a  little 
weak  sulphuric  acid,  a  red  liquid  will  be  obtained.  If  to  the  other  a  solution 
of  an  alkali  be  added,  as  potash  or  soda,  a  liquid  of  a  green  color  is  formed. 
On  gradually  adding  the  alkaline  solution  to  the  other,  stirring  the  mixture 
constantly,  the  green  color  of  the  portions  first  added  instantly  disappears,  and 
the  whole  liquid  remains  red ;  as  more  and  more  of  the  solution  containing 
the  alkali  is  added,  the  red  by  degrees  passes  into  purple,  and  on  continuing 
to  add  it,  a  point  is  reached  when  the  original  red  liquid  acquires  a  clear  blue 
tint.  At  this  moment  there  is  neither  free  alkali  or  free  acid  in  the  liquid,  for 
the  two  have  chemically  united  with  each  other,  and  have  lost  their  charac- 
teristic properties.  If  the  solution  be  now  evaporated  at  a  gentle  heat,  a 
solid  crystalline  substance  is  obtained,  resulting  from  the  combination  of  the 
sulphuric  acid  with  the  potash.  This  substance  is  a  salt,  and  is  called  sul- 
phate of  potash.* 

The  acids  and  the  alkalies  are  both  remarkable  for  their  great  chemical 
activity.  The  acids  dissolve  all  the  metals,  even  the  most  compact.  They 
also,  except  when  very  weak,  destroy  the  skin  and  nearly  all  animal  and 
vegetable  substances.  The  action  of  the  alkalies,  especially  potash  and  soda, 
is  no  less  marked.  They  destroy  the  skin,  if  allowed  to  remain  on  it.  and 
gradually  remove  the  glaze  from  vessels  of  glass  and  earthen- ware  which 
contain  them.  They  also  quickly  remove  paint  from  the  surface  of  any 
object  upon  which  their  solutions  fall.  But  the  most  remarkable  property  of 
acids  and  alkalies,  is  the  power  which  they  have  of  uniting  with  each  other, 
and  destroying,  or  neutralizing  the  chemical  activity  which  distinguishes  them 
when  separate. 

No  simple  or  elementary  substance  has  the  properties  of  either  an  acid  or 
alkali.  Consequently,  all  acids  and  alkalies  are  compounds  of  two  or  more 
elements. 

266.  Neutral  Bodies, — A  substance  which  possesses 
neither  the  properties  of  an  acid  or  a  base,  is  termed 
neutral. 

*  In  practical  chemistry,  a  blue  substance,  called  "litmus,"  extracted  from  a  species 
of  lichen,  is  used  extensively  for  determining  the  presence  of  an  acid  or  alkali.  Paper, 
colored  blue  with  the  tincture  of  litmus,  is  instantly  changed  to  red  by  contact  with  the 
most  minute  quantity  of  an  acid  in  solution ;  and  the  red  color  thus  obtained  is  as  quickly 
destroyed,  and  the  original  blue  restored  by  the.  action  of  an  alkali.  Little  strips  of 
blue  and  red  paper  thus  prepared,  are  kept  constantly  on  hand  in  the  laboratory,  and 
are  designated  as  "  test  papers.1' 

QUESTIONS. — How  may  the  properties  of  the  acids  and  alkalies  be  illustrated?  What 
are  the  characteristic  properties  of  acids  and  alkalies  ?  Does  any  simple  substance  possess 
the  properties  of  an  acid  or  alkali  ?  What  are  the  neutral  bodies  ? 


176  INORGANIC     CHEMISTRY. 

"Water  is  the  perfection  of  a  neutral  substance,  although,  in  some  instances, 
it  may  supply  the  place  of  an  acid  or  a  base. 

267.  Origin  of  Chemical  Nomenclature. — The  principles 
npon  which  chemical  nomenclature  is  founded,  were  established  by  a  com- 
mittee of  the   French  Academy  in  1787.     It  was  found  that  owing  to  the 
rapid  progress  of  science,  the  number  of  new  chemical  substances  increased 
so  fast,  that  unless  some   uniform  system  of  naming  and  classifying  were 
adopted,  the  most  inextricable  confusion  would  result.    The  committee,  there- 
fore, devised  a  nomenclature  which  aims  not  merely  to  give  a  distinguishing 
name  to  the  substances  spoken  of,  but  also  to  convey  a  knowledge  of  their 
components,  and  even  of  the  proportions  in  which  those  components  occur. 
This  object  was  in  a  great  degree  attained  to,  and  the  system  then  instituted 
remains  in  use,  so  far  as  its  essential  features  are  concerned,  to  the  present 
day. 

268.  Nomenclature  of  the  Elements  , — The  elements  which 
have  been  known  from  the  most  remote  period  retain  their  common  names, 
and  also  their  Latin  names,  to  a  considerable  extent — as  for  example,  Iron 
(FeirumX  Gold  (Aurum),  Copper  (Cuprum),  Mercury  (Hydragyrum),  Silver 
(Argentum),  Lead  (Plumbum),  Tin  (Stannum).    If  the  element  has  been  made 
known  in  modern  times  through  chemical  research,  the  name  it  bears  gener- 
ally indicates  some  distinguishing  feature  by  which  it  is  characterized ;  thus, 
Phosphorus  (from  the  Greek  0«f,  light,  and  $epu  to  bring),  from  its  property 
of  shining  in  the  dark;  Chlorine  (from  ^Awpof,  green),  from  its  peculiar  color; 
Bromine,  from  /3p£/*ofr  a  stench,  etc.     To  the  recently  discovered  metals,  a 
common  termination  in  um  has  been  assigned,  as  Platinum,  Palladium,  Indium, 
Potassium,  Sodium,  Aluminum,  etc. 

269.  Nomenclature  of  Compounds  , — When  two  elements  unite, 
the  product  is  called  a  binary  compotmd~^Irom  lis,  twice) ;  thus,  water,  com- 
posed of  oxygen  and  hydrogen,  sulphuric  acid,  composed  of  oxygen  and  sul- 
phur, and  oxyd  of  iron,  composed  of  oxygen  and  iron,  are  examples  of  binary 
compounds. 

Compounds  of  binary  combinations  with  each  other,  as  sulphuric  acid  with 
oxyd  of  iron,  are  called  ternary  compounds  (from  ter,  thrice),  three  elements 
being  concerned.  Most  of  the  minerals  are  ternary  compounds. 

Combinations  of  salts  with  each  other  are  named  quaternary  compounds, 
or  double  salts.  Alum  is  an  example,  being  a  compound  of  sulphate  of  pot- 
ash and  sulphate  of  aluminum. 

Compounds  of  oxygenjare  termed  oxyds.  Thus  water 
is  an  oxyd  of  hydrogen,  iron-rust  an  oxyd  of  iron. 

The  binary  compounds  of  chlorine,  bromine,  iodine,  fluorine,  and  several 
other  elements  which  resemble  oxygen  in  their  mode  of  combination,  are 

QTTESTIONS. — What  was  the  origin  of  the  chemical  nomenclature  nov  in  use?  What  is 
the  general  nomenclature  of  the  elements?  What  are  binary  compounds?  What  are 
examples?  What  are  ternary  compounds?  Give  examples.  What  are  quaternary 
compounds?  What  are  examples?  What  are  compounds  of  oxygen  called?  What  the 
compounds  of  chlorine,  iodine,  fluorine,  etc.  ? 


PRINCIPLES    OF   CHEMICAL    PHILOSOPHY.      177 

distinguished  by  the  final  termination  ide,  Thug  chlorine  forma  chlorides ; 
iodine,  iodides;  fluorine,  fluorides ;  sulphur,  sulphides,  etc.* 

When  oxygen  combines  with  the  same  element  in  more  than  one  propor- 
tion, forming  different  oxyds,  the  several  combinations  are  distinguished  from 
each  other  by  the  use  of  prefixes.  Thus,  the  first  oxyd,  or  the  one  which 
contains  but  one  equivalent  of  oxygen,  is  known  as  the  Protoxide  (from  the 
Greek  Trpwrof,  the  first) ;  the  compound  of  two  proportions  is,  in  like  manner, 
designated  as  the  deutoxyd  (dsvrepo^  double),  and  also  as  the  binoxyd  (/3i, 
double) ;  the  compound  of  three  proportions  is  also  known  as  the  tritoxyd 
(rpiTor,  third). 

The  oxyd,  also,  which  contains  the  largest  proportion  of  oxygen  with 
Which  the  body  is  known  to  unite,  is  termed  the  peroxyd.  In  like  manner, 
the  highest  combinations  of  chlorine,  sulphur,  iodine,  etc.,  are  termed  per- 
chlorides,  persulphides,  periodides, 

For  example,  oxygon  unites  with  hydrogen  in  two  proportions  :  the  first 
combination  is  the  protoxyd  of  hydrogen  (water);  the  second  and  highest 
is  the  peroxyd,  Again,  with  manganese,  oxygen  unites  in  three  propor- 
tions :  the  first  is  termed  the  protoxyd,  the  second  the  deutoxyd,  or  binoxyd, 
and  the  third  the  peroxyd. 

With  some  elements  oxygen  enters  into  combination  in  the  proportion 
of  3  to  2,  or  in  the  ratio  of  l£  of  oxygen  to  1  of  the  element,  Such  a  com- 
pound is  termed  a  sesquioxyd  (from  the  numeral  sesqui,  once  and  a  half). 
Certain  other  oxygen  compounds  are  formed  in  the  proportion  of  2  of  the 
element  to  1  of  oxygen ;  Buch  are  termed  suboxyds,  as  the  suboxyd  of 
copper. 

When  the  compounds  formed  by  the  union  of  oxygen  with  the  different 
elements  possess  an  acid  character  (as  very  many  of  them  often  do),  a  different 
plan  is  adopted  to  mark  this  peculiarity.  The  compound  is  then  termed  an 
acid,  and  its  name  is  derived  from  the  substance  which  combines  with  the 
oxygen,  with  the  termination  ic  added.  Thus,  sulphur  with  oxygen  gives  sul- 
phuric acid ;  carbon  with  oxygen,  carbonw;  acid ;  and  phosphorus  with  oxygen, 
phosphoric  acid,  It  frequently  happens,  however,  that  an  element  forma 
more  than  one  acid  with  oxygen,  When  this  is  the  case,  the  termination  ic 
is  applied  to  the  strongest  acid,  and  ous  to  the  weaker.  Thus  we  have  sulphuric 
and  sulphurous  acids,  nitric  and  nitrous  acids, 

The  salts  which  these  and  other  similar  acids  form  by  uniting  with  bases, 
are  named  in  an  equally  simple  manner,  the  acid  supplying  the  generic,  and 
the  base  the  specific  name :  the  ous  termination  of  the  acid  is  also  changed 
into  tie,  and  ic  termination  into  ate.  Thus,  sulphite  of  soda,  nitrite  of  potassa, 


*  Binary  compounds  of  sulphur,  phosphorus  and  Carbon,  are  also  Very  generally  know 
by  the  termination  uret,  as  sulphuret  of"  iron,  carburetted  hydrogen,  etc. 

QTTEBTIONS.-— How  are  the  first,  Second  and  third  oxyds  distinguished  ?  What  is  a  per- 
oxyd ?  What  is  a  protoxyd  ?  What  is  a  perchloride  ?  What  is  a  binoxyd  ?  What  are 
sesquioxyds  ?  What  are  suboxyds  ?  How  are  acid  compounds  of  oxygen  named  ? 


178  INORGANIC     CHEMISTRY. 

sulphate  of  soda,  and  nitrate  of  potassa,  are  salts  respectively  of  sulphurous, 
nitrous,  sulphuric  and  nitric  acids.* 

'  This  nomenclature  served  to  distinguish  these  acids  and  their  salts  until,  -aa 
the  science  of  chemistry  advanced,  a  compound  of  oxygen  and  sulphur  was 
discovered  containing  less  oxygen  than  the  sulphurous,  and  then  a  new  name 
was  required ;  it  was  therefore  called  hyposulphurous  acid,  and  the  -salt  formed 
with  it  is  termed  a  hyposulphite  (from  the  Greek  v~d,  under) ;  so  also,  when 
an  acid  was  discovered  containing  less  oxygen  than  the  sulphuric,  but  more 
than  the  sulphurous,  it  was  called  hyposulphuric,  and  its  salt  a  hyposulphate. 
In  some  cases  acids  have  been  discovered  containing  more  oxygen  than  those 
already  named  with  terminations  in  ic ;  to  these  the  prefix  hyper  (from  the 
Greek  virtp,  over)  is  attached.  Thus  chloric  acid  was  for  a  very  long  time 
the  highest  oxygen  compound  with  chlorine,  but  another  still  higher  is  now 
known.  The  last,  therefore,  is  designated  as  hyporchloric,  and  sometimes  as 
perchloric  acid.  Its  salts  are  called  hyperchlorates. 

270.  Classification  of  A_c  i  d  s , — It  was  once  supposed  that  the  pres- 
ence of  oxygen  in  a  substance  was  essential  to  its  acidity,  but  the  progress  of 
research  has  revealed  the  existence  of  acids  which  are  entirely  wanting  hi 
oxygen.     Most  of  the  acids  which  are  wanting  in  oxygen  contain  hydrogen 
in  its  place.     They  are  distinguished  by  prefixing  to  them  the  word  hydro, 
as  an  abbreviation  for  hydrogen.     Thus,  chlorine  and  hydrogen  form  an  acid, 
hydrochloric  acid,  often  called  muriatic  acid ;  cyanogen  and  hydrogen  form 
hydrocyanic  acid,  or  prussic  acid ;  sulphur  and  hydrogen  form  hydrosulphuric 
acid,  etc.f     Some  chemists,  especially  the  French,    transpose  these  terms; 
they  speak  of  chlorhydric  acid,  cyanhydric  acid,  sulphydric  acid,  etc.     There 
is  an  advantage  in  this  alteration,  as  it  avoids  any  ambiguity  which  might 
arise  from  the  use  of  the  prefix  hydro,  which  has  sometimes  been  applied  to 
compounds  which  contain  water. 

271.  Classification   of   Smalts . — In  the  early  days  of  chemistry, 
the  term  salt  was  applied  to  all  substances  indifferently,  which  resembled  com- 
mon salt  in  appearance  and  properties.     Subsequently,  the  use  of  the  term 
was  restricted  to  those  compounds  only  which  were  formed  by  the  union  of 
an  acid  and  a  base :  but  when  chemical  knowledge  had  still  further  progressed, 


*  It  may  here  be  Well  to  caution  those  who  arc  just  commencing  the  study  of  chemistry, 
of  the  necessity  of  distinguishing  clearly  between  compounds  such  as  the  sulphites  and 
the  sulphates,  or  the  sulphides  and  the  sulphites.  Sulphide  of  sodium  is  a  binary  com- 
pound of  two  elementary  bodies,  sodium  and  sulphur  ;  sulphite  of  soda  is  a  more  complex 
compound,  formed  by  the  union  of  sulphurous  acid  and  the  oxyd  of  sodium  (soda) ;  sul- 
phate of  soda  is  formed  by  the  union  of  sulphuric  acid  and  soda. 

t  The  acids  formed  by  the  union  of  sulphur  and  arsenic  with  hydrogen  are  also  very 
commonly  known  as  sulphuretted  hydrogen,  and  arseniuretted  hydrogen. 

QUESTIONS. — How  are  the  different  acid  compounds  distinguished  ?  How  are  salts 
named  ?  What  gives  the  generic  and  what  the  specific  name  to  a  salt  ?  How  do  acids  in 
forming  salts  change  their  terminations  ic  and  ous  ?  What  do  the  prefixes  hypo  and 
hyper  designate  ?  Is  the  presence  of  oxygen  essential  to  the  existence  of  an  acid  ?  What 
element  generally  supplies  the  place  of  oxygen  in  acids  wanting  this  element  ?  How  are 
hydrogen  acids  named  ? 


PRINCIPLES    OF    CHEMICAL     PHILOSOPHY.      179 

it  was  found  that  if  this  definition  was  rigidly  enforced,  it  would  exclude  from 
the  class  of  salts  a  considerable  number  of  compounds  which  possess  the 
physical  characteristics  of  a  salt  in  a  most  eminent  degree.  Among  these 
was  common  salt  itself,  which,  although  the  type  of  all  salts,  is  not  a  com- 
pound of  an  acid  or  a  base,  but  a  compound  of  two  elements,  chlorine  and 
sodium.  In  like  manner,  the  compounds  of  iodine,  bromine,  and  fluorine 
with  the  metals,  possess  in  a  very  high  degree  the  saline  character.  To  ob- 
viate, therefore,  the  somewhat  startling  proposition,  that  common  salt  is  no 
salt  at  all,  and  to  avoid  doing  violence  to  a  long-received  and  expressed  com- 
mon idea,  two  classes  of  salts  were  established. 

The  first  class  includes  all  those  binary  compounds  which,  like  common 
salt,  are  formed  by  the  direct  union  of  a  metal  with  some  other  substance, 
called  a  salt  radical,  as  chlorine,  fluorine,  bromine,  etc.  Compounds  of  this 
character  are  termed  Haloid  Salts. 

Radical . — The  term  radical  in  chemistry,  is  generally  applied  to  any 
substance^  simple  or  compound,  which  can  unite  with  hydrogen  to  form  an 
acid  compound,  and  with  a  metal  to  form  a  salt. 

The  second  class  includes  all  those  salts  formed  by  the  union  of  an  acid 
and  a  base.*  These  are  termed  oxy-salts,  or  oxygen  acid  salts. 

Many  of  the  compounds  of  sulphur  with  the  metals,  as  the  compound  of 
sulphur  and  potassium,  also  possess  a  saline  character,  and  are  termed  sul- 
phur salts. 

Such  in  general  are  the  principles  of  chemical  nomenclature,  as  established 
by  the  Committee  of  the  French  Academy.  As  before  said,  the  object  of  the 
inventors  of  this  language  was  not  only  to  give  a  distinguishing  name  to  the 
substances  spoken  of,  but  also  to  convey  a  knowledge  of  its  chemical  compo- 
sition. That  this  has  been  accomplished  in  a  great  degree,  will  be  evident 
from  one  or  two  illustrations.  Thus,  the  name  bi-chromate  of  potash  indicates 
by  simple  inspection  that  the  substance  is  an  oxygen  acid  salt,  composed  of 
chromic  acid  and  potash,  the  prefix  bi  showing  that  the  equivalent  or  pro- 
portion of  acid  to  base  is  as  two  to  ore.  Again,  the  name  permanganate  of 
potash  indicates  a  compound  of  manganic  acid  and  potash,  and  the  prefix  per 
shows  that  the  acid  in  question  is  the  highest  oxygen  compound  of  mangan- 
ese known. 

272.  Symbols. — Although  the  chemical  nomenclature  in  use  is  most 
convenientp-and  perhaps  as  perfect  in  principle  as  the  nature  of  our  language 


*  A  beautiful  illustration  of  the  universality  of  the  law,  that  bodies  replace  each  other 
4n  combination  in  fixed  equivalent  quantities,  is  found  in  the  combination  of  salts.  Thus, 
when  equivalents  of  two  neutral  salts,  which  are  capable  of  decomposing  each  other,  are 
brought  into  chemical  contact  with  each  other,  the  two  bases  exchange  acids  by  an  exact; 
compensation ;  the  original  compounds  are  altogether  lost,  and  two  new  salts  evolved, 
without  either  loss  or  addition  of  any  kind  in  the  process. 

QTTESTIONS.— What  two  classes  of  salts  have  been  recognized  in  chemistry?  What  art 
haloid  salts  ?  What  are  oxysalts  ?  What  are  sulphur  salts  ?  Illustrate  by  example  the 
manner  in  which  the  chemical  name  of  a  substance  indicates  its  composition.  What  In 
the  necessity  of  using  symbols  In  chemistry? 


180  INORGANIC     CHEMISTRY. 

•will  allow,  yet  the  impracticability,  in  many  cases,  of  contriving  convenient 
names  expressive  of  the  constitution  of  many  complex  chemical  compounds 
(the  existence  of  some  of  which  was  hot  known  or  even  anticipated  by  the 
inventors  of  chemical  language),  has  led  to  the  employment  of  symbols. 
These  constitute  a  species  of  short-hand,  which  not  only  supplies  all  de- 
ficiencies of  the  nomenclature,  but  enables  us  to  represent  to  the  eye,  and 
describe  with  mathematical  accuracy  and  rapidity  the  known  composition  of 
every  chemical  substance,  and  the  changes  which  it  may  undergo.  The  em- 
ployment of  symbols  has  now  become  universal,  and  is  also  indispensable  to 
both  teacher  and  student  in  the  study  of  chemistry. 

273^  Symbols  of  Elements, — It  has  been  agreed  by  all 
chemists  to  use,  as  symbols  of  the  elements,  the  first  let- 
ter of  their  Latin  names.  When  two  or  more  names  com- 
mence with  the  same  initial,  a  second  distinguishing  letter 
is  added. 

In  the  table  of  elementary  bodies,  the  symbol  of  the  several  elements  will 
be  found  opposite  to  their  names. 

The  symbols,  when  used  singly,  represent  not  merely  the  element  for  which 
they  stand,  but  one  equivalent  of  that  element.  Thus,  the  symbol  0  stands 
not  for  oxygen  in  general,  but  for  one  equivalent  of  oxygen,  or,  hydrogen 
being  unity,  for  the  number  8.  H,  in  like  manner,  stands  for  one  equivalent 
of  hydrogen,  and  the  number  1 ;  C  for  one  equivalent  of  carbon,  and  the 
number  6 ;  Pb  for  one  equivalent  of  lead,  and  the  number  104. 

If  more  than  one  equivalent  of  a  body  has  to  be  expressed,  it  is  signified 
either  by  writing  a  small  figure  to  the  right  of  the  symbol,  and  generally  be- 
low the  line.  Thus — 

Oa  stands  for  2  equivalents,  or  16  of  oxygen. 
0s          "        5  "          or  40       " 

The  same  may  be  represented  also  by  prefixing  the  number  to  the  symbol, 
as  20,  5O. 

The  symbol  may  also  be  considered  as  representing  the  atomic  constitution 
of  a  body.  For  example,  O  stands  for  one  atom  of  oxygen  as  well  as  for 
one  equivalent ;  Oa  for  two  atoms ;  O&  for  five  atoms. 

274.  Symbols  of  Compounds.— In  order  to  form  the 
symbol  of  a  compouncTpwe  unite  the  symbols  of  the  ele- 
ments of  which  it  consists,  one  after  the  other,  indicating 
by  means  of  figures  the  number  of  each  which  have  en- 
tered into  combination. 

'  Thus,  HO  is  the  symbol  of  water,  a  compound  consisting  of  one  equivalent, 
or  1  of  hydrogen,  and  of  one  equivalent,  or  8  of  oxygen;  80s  is  the  symbol 

QUESTIONS. — What  symbols  are  used  to  designate  the  elements?  What  does  a  single 
symbol  of  an  element  represent  ?  How  are  several  equivalents  of  an  element  represented 
by  symbols  ?  How  is  the  constitution  of  compounds  represented  by  symbols  ? 


PRINCIPLES     OF     CHEMICAL     PHILOSOPHY.      181 

of  sulphuric  acid,  a  compound  consisting  of  one  equivalent,  or  1G  of  sulphur, 
and  throe  equivalents,  or  24  of  oxygen.  €12  HH  On  is  the  symbol  of  com- 
mon sugar,  a  compound  consisting  of  twelve  equivalents  of  carbon,  eleven 
equivalents  of  hydrogen,  and  eleven  equivalents  of  oxygen. 

A  collection  of  symbols  indicating  the  constitution  of  compounds,  is  called 
a  formula. 

Compounds  united  with  compounds,  such  as  salts,  are  expressed  in  a  simi- 
lar manner,  the  base  of  the  salt,  or  the  electro-positive  element,  being  always 
placed  first.  Thus,  sulphuric  acid  has  the  formula  80s,  and  oxyd  of  iron, 
that  of  FeO,  consequently  the  formula  FeO-j-SOs  will  represent  one  equiva- 
lent of  sulphate  of  the  protoxyd  of  iron.  Frequently  a  comma  is  placed  be- 
tween the  two  compounds  instead  of  the  algebraic  sign  -f--  Thus,  sulphate 
of  iron  may  be  written  FeO,  80s.  This  mode  is  usually  adopted  to  express 
a  more  intimate  union  than  when  the  sign  -f-  is  used.  Thus,  SO,  HO,-{-2  HO 
indicates  that  an  equivalent,  or  compound  atom  of  sulphuric  acid  has  united 
with  three  equivalents  of  water,  two  of  which  are  loosely  retained,  and  ono 
very  strongly. 

"Where  it  is  necessary  to  indicate  more  than  one  equivalent  of  a  compound, 
the  whole  formula  of  that  compound  is  included  in  a  bracket,  and  preceded 
by  the  indicating  number.  Thus,  three  equivalents  of  sulphate  of  iron  would 
be  written  3  [FeO,  80s].  The  figure  prefixed  multiplies  nothing  beyond 
the  symbols  included  within  the  bracket.  Thus,  in  the  formula  for  crystal- 
lized alum — 

Als  08,  3[SOg]+KO,  SOs+24  HO, 

the  3  which  precedes  S  Os  only  indicates  that  three  equivalents  of  sulphuric 
acid  are  present.  Frequently  the  employment  of  brackets  is  neglected,  and 
then  the  figures  multiply  all  the  symbols  included  between  them  and  the  next 
comma  or  sign  of  addition. 

275.  Reactions  and  Reagents,— The  various  chemical 
changes,  to  which  all  matter  is  more  or  less  liable,  are 
termed,  in  the  language  of  chemistry,  reactions  and  the 
agents  which  cause  these  changes,  reagents. 

In  addition  to  the  information  which  symbols  convey  relative  to  the  com- 
position of  the  substances  for  which  they  stand,  they  can  also  be  so  combined 
in  the  form  of  equations,  as  to  show  in  the  most  perfect  manner  the  various 
products  which  result  from  chemical  reactions.  For  this  purpose,  the  symbols 
of  the  substances  involved  in  the  reactions  are  placed  together,  so  as  to  form 
one  side  of  the  equation,  and  the  symbols  of  the  products  resulting  from  the 
reactions  on  the  other  side.  But  as  not  the  smallest  particle  of  matter  can  be 
annihilated  by  any  chemical  action,  it  follows  that  the  value  of  both  sides  of 


.— What  are  chemical  formulae?  How  is  the  composition  of  salts  Indicated 
by  symbols?  Which  constituent  of  a  salt  is  placed  first?  What  does  the  sign  +  mean? 
What  is  to  be  understood  by  the  terms  reactions  and  reagents  ?  How  may  symbols  be 
arranged  so  as  to  indicate  chemical  reactions  and  their  products  ? 


182  INORGANIC     CHEMISTRY. 

the  equation  must  be  equal  or  in  other  words,  the  sum  of  the  weights  of  the 
products  of  every  reaction  must  be  always  equal  to  the  sum  of  the  weights 
of  the  substances  involved  in  the  change.  For  example,  the  decomposition 
of  carbonate  of  lime  (marble)  by  sulphuric  acid,  and  the  liberation  of  carbonic 
acid  gas  may  be  represented  by  the  following  equation : 

20+8,  -H6-J-16,  -j-16+24=20-[-8,+16+244-6-|-16=90. 
Ca    0,    G    02-fS     Os=Ca    0,      S     Og+C    02. 

The  correctness  of  this  equation  may  be  proved  by  adding  together  the 
equivalents  of  both  sides,  when  the  sums  will  be  found  to  be  equal. 

A  very  little  practice  will  render  the  use  of  symbols  familiar  to  all.  To 
expedite  the  acquisition  of  this  knowledge,  the  student  will  find  it  advan- 
tageous to  exercise  himself  in  the  expression  of  chemical  changes  by  sym- 
bols, whenever  the  opportunity  occurs,  until  he  is  thoroughly  acquainted  with 
their  signification  and  use. 

276.  Is  ojnje  r  i  s  m . — Until  within  a  recent  period,  it  was  an  acknowledged 
principle,  that  two  bodies  containing  the  same  elements  combined  in  exactly 
the  same  proportion,  must  of  necessity  possess  the  same  properties,  and  be 
mutually  convertible  into  each  other.  Such,  however,  is  not  the  fact,  and 
numerous  substances  are  now  known  to  exist,  which  are  identical  in  chemical 
composition  and  yet  exhibit  totally  distinct  physical  and  chemical  properties. 
Different  bodies  thus  agreeing  in  composition  but  differing  in  properties,  are 
said  to  be  isomeric  (from  urof,  equal,  and  /zepoj-,  part),  and  the  phenomenon  in 
general  is  termed  Isomerism. 

A  great  class  of  bodies  known  as  the  volatile  oils,  oil  of  turpentine,  oil  of 
rosemary,  oil  of  lemons,  and  many  others,  are  examples  of  bodies  which  dif- 
fer widely  from  each  other  in  respect  to  odor,  medicinal  effects,  boiling  point, 
specific  gravity,  etc.,  and  yet  are  exactly  identical  in  composition — that  is, 
they  contain  the  same  elements,  carbon  and  hydrogen,  in  the  same  propor- 
tions.* "  The  crystallized  part  of  the  oil  of  roses,  the  delicious  fragrance 
of  which  is  so  well  known,  a  solid  at  ordinary  temperatures,  although  readly 
volatile,  is  a  compound  body  containing  exactly  the  same  elements,  and  in 
the  same  proportion,  as  the  gas  we  employ  for  lighting  our  streets." 

The  difference  of  properties  in  isomeric  bodies  is  explained  very  simply  by 
the  atomic  theory.  "  It  is  supposed  that  the  atoms  in  each  particular  case 
are  differently  arranged,  in  the  same  way  as  the  most  manifold  grouping  may 
be  produced  on  a  chess-board  by  transposition  of  the  white  and  black  squares, 
as  is  shown  in  Fig.  76.  Each  figure  is  composed  of  eight  white  and  eight 
black  squares,  but  though  the  absolute  number  is  the  same,  the  grouping  is 
different.  In  a  one  and  one,  in  b  two  and  two,  in  c  and  d  four  and  four 


*  Two  conditions  of  isomcrism  may  be  noted  ;  one  in  -which  the  absolute  number  of 
atoms,  and  consequently  the  atomic  weight  of  the  compound,  is  the  same ;  the  other 
where,  though  the  relative  proportions  of  the  elements  are  the  same,  the  absolute  num- 
ber of  atoms  of  each  is  different 


QTTESTIONB.— Illustrate  this  by  example.     What  is  isomerism?     Give  examples  of 
isomeric  bodies.    How  is  isomerism  explained  ? 


PRINCIPLES    OF    CHEMICAL    PHILOSOPHY.      183 

squares  aro  so  joined  as  to  present  a  different  appearance.  If  we  imagine 
these  squares  to  be  atoms,  we  obtain  an  idea  of  isomeric  bodies,  and  it  is  thus 
rendered  clear  how  there  may  bo  bodies  of  the  same  constitution  and  form, 


yet  presenting  an  entirely  different  appearance  and  possessing  different  prop- 
erties.' ' — STOC  K  n  ARDT. 

277.  Allot  ropism  . — Many  of  the  elements  are  capable  of  existing  in 
two  or  more  different  conditions,  or  forms,  in  each  of  which  they  manifest 
different,  and  often  opposite  properties.  This  principle  is  termed  Allotropism, 
and  bodies  manifesting  changes  of  such  character  are  called  Allotropic  (from 
tU/lorpoTrof,  different  nature). 

One  of  the  most  striking  illustrations  of  allotropism  is  to  be  found  in  the 
case  of  the  element  carbon,  which  exists  in  a  pure  state  in  the  brilliant  trans- 
parent diamond,  in  the  opaque  and  black  charcoal,  and  in  the  mctallic-like 
body  known  as  graphite,  or  black-lead.  Sujphur,  phosphorus,  silicon,  boron, 
oxygen,  and  other  elements,  are  susceptible  of  similar  changes. 

Bodies  in  allotropic  conditions  differ  in  their  chemical  as  well  as  in  their 
physical  properties.  Carbon  as  the  diamond  is  almost  incombustible  ;  carbon 
as  lamp-black  inflames  at  a  low  temperature,  and  sometimes  ignites  sponta- 
neously. Phosphorus,  in  the  ordinary  condition,  is  soft,  yellowish  in  color, 
has  a  powerful  smell  and  taste,  and  can  scarcely  be  handled  with  impunity, 
since  it  bursts  into  a  flame  at  a  temperature  a  little  above  that  of  the  human 
body ;  allotropic  phosphorus,  on  the  contrary,  is  of  a  black  color,  hard,  de- 
void of  both  smell  and  taste,  and  may  bo  handled  without  danger,  and  bo 
even  carried  in  one's  pocket. 

The  explanation  of  allotropism  is  referred  to  difference  in  the  'arrangement 
of  the  particles  or  atoms  constituting  the  body.  Thus  the  same  fibres  of  cot- 
ton, when  closely  matted  together,  constitute  hard,  tough  paper ;  when  simply 
carded,  wadding ;  when  twisted,  yard,  or  thread  ;  and  when  intertwined,  cloth. 

QUESTIONS. — What  is  allotropism  ?  What  are  examples  of  allotropism  ?  IIow  is  this 
condition  explained  ? 


184  INOKGAN1C    CHEMISTRY. 

CHAPTER    VI. 

THE    NON-METALLIC    ELEMENTS, 

278.  The  generally  recognized  division  of  the  simple  substances  into  Metal- 
lic and  Non-metallic  elements,  or  the  Metals  and  Metalloids,  (from  /nera/^ov, 
metal,  and  si6o^  appearance,)  although  most  convenient  for  description,  is 
not  established  in  nature,  and  no  strict  line  of  separation,  moreover,  between 
the  two  classes  can  be  indicatedpsTnce  some  of  the  elements  possess,  in  a 
nearly  equal  degree,  the  characteristics  of  both, 

Metalloids, — The  number  of  the  elements  generally 
included  in  the  class  of  metalloids  is  fourteen,  which 
may  be  enumerated  as  follows  : — -Oxygen,  Hydrogen, 
Nitrogen,  Chlorine,  Iodine,  Bromine,  Fluorine,  Sulphur, 
Selenium,  Tellurium,  Phosphorus,  Silicon,  Boron,  and 
Carbon. 

Characteristics  of  the  Metalloids  .—The  characteristics 
which  serve  in  general  to  distinguish  the  metalloids  from  the  metals  are 
as  follows: — They  do  not  possess  a  metallic  appearance,  and  are  bad  con- 
ductors of  heat  and  electricity.  When  binary  compounds  of  the  metals  and 
metalloids  are  decomposed  by  the  agency  of  galvanism,  the  metalloids  always 
separate  at  the  positive  pole  (the  zinc  side),  and  the  metals  at  the  negative 
pole;  as  bodies  endowed  with  opposite  electricities  only  are  attracted,  the 
metalloids  are,  for  this  reason,  termed  electro-negative  elements,  and  the 
metals  electro-positive  elements.  Almost  all  the  metalloids  combine  with 
hydrogen,  but,  as  a  general  rule,  the  metals  do  not. 

SECTION    I. 

OXY  GEN. 
Equivahni  8.  Symbol  0.  Density  1-1.  (Air»*l.) 

279.  II  i  R  t  o  r  y, — Oxygen  gas  was  discovered  by  Dr.  Priest- 
leyj  an  English  clergymen,  in  1774.     He  called  it  depho- 
gisticated  air. 

In  the  following  year  it  was  again  discovered  by  Scheele,  a  Swedish  chemist, 
and  by  Lavoisier,  the  illustrious  French  chemist,  without  cognizance  of  Priest- 
ley's discovery.     The  latter,  supposing  it  to  be  the  sole  agent  which  imparted " 
to  bodies  their  acid  properties,  gave  it  its  present  name,  oxygen,  (from  o&c, 
acid,  and  yevaw,  I  give  rise  to). 

QUESTIONS.— How  are  the  elements  divided  ?  Is  this  division  founded  in  nature  ?  How 
many  of  the  elements  are  generally  Included  among  the  metalloids?  Name  them.  What 
are  the  characteristics  of  the  metalloids  ?  When  and  by  whom  was  oxygen  discovered  1 
From  whom  did  oxygen  derive  its  name  ? 


OXYGEN. 


185 


280.  Natural  History  and  D  is  tri  but  ion.  —  Oxygen  is  the 
most  abundant  of  all  the  elementary  substances,  but  is  never  met  with  in  na- 
ture in  a  pure  or  isolated  condition.     It  constitutes  at  least  one  third  part  of 
the  solid  crust  of  the  globe,  eight-ninths  by  weight  of  all  the  water  upon  its 
surface,  more  than  one  fifth  of  the  atmosphere,  and  eight-ninths  of  the  vapor 
contained  in  the  atmosphere.     It  is  also  an  essential  constituent  of  all  living 
structures,  and  is  the  immediate  agent  by  which  animal  life  and  all  the  pro- 
cesses of  combustion  are  sustained. 

The  meteoric  masses  which  fall  to  the  earth  from  the  inter  planetary  spaces, 
have  little  or  no  oxygen  in  their  composition,  and  in  this  respect  they  are 
unlike  any  of  the  compound  substances  which  compose  the  crust  of  the  globe. 
Hence  the  inference  has  been  drawn,  that  in  some  of  the  great  planetary  masses 
of  the  solar  system,  from  whence  meteorites  are  undoubtedly  derived,  oxygen 
does  not  exist  at  all,  or  in  much  smaller  proportions  than  upon  the  earth. 

281.  Preparation,  —Many  solid  substances,  which  con- 
tain oxygen  in  combination,  readily  evolve  it  in  a  gaseous 
form  when  subjected  to  a  sufficiently  high  temperature. 

A  very  easy  method  of  obtaining  a  small  quantity  of  oxy-  ^ 
gen  gas  for  experiment,  which  at  the  same  time  illustrates  the 
original  process  by  which  Priestley  discovered  it,  is  to  heat 
a  little  of  the  red  oxyd  of  mercury  in  a  thin  glass  tube  (Fig. 
77)  over  a  spirit-lamp.*  In  this  substance  the  affinity,  or 
chemical  attraction  which  holds  together  the  mercury  arid 
the  oxygen  is  so  feeble,  that  a  very  slight  degree  of  heat 
Buffices  to  bring  about  decomposition ; — the  mercury  collecting 
in  small  globules  on  the  bottom  and  sides  of  the  tube,  and  ^ 
the  oxygen  escaping  as  a  gas.  The  presence  of  the  latter 
element  may  be  demonstrated  by  holding  an  ignited  sub-: 
stance  over  the  mouth  of  the  tube. 

If  it  is  desired  to  collect  and  preserve  the  oxygen  liberated 
in  this  experiment,  one  end  of  a  bent  glass  tubef  is  fitted  by  means  of  a  per- 

•  Cylindrical  glass  tubes,  with  rounded  bot-  FIG.  78. 

toms,  known  as  "  test  tubes,"  are  generally  used 
in  chemical  experimentation.  A  simple  wooden 
rack,  as  in  Fig.  78,  serves  as  a  convenient  stand 
for  them.  Teachers  will  do  well  to  furnish 
themselves  with  a  supply  of  these  tubes,  as  they 
are  inexpensive,  and  can  be  use  for  a  great  va- 
riety of  purposes. 

t  Glass  tubing  prepared  expressly  for  chemical 
manipulations  can  be  procured  at  a  small  expense 
of  any  dealer  in  chemical  apparatus.  By  means 
of  a  Berzelius  spirit-lamp,  and  with  a  little  prac- 
tice, an  inexperienced  person  can,  in  a  short  time,  learn  to  bend  and  adapt  his  tubing 
to  his  apparatus  with  ease  and  rapidity. 

QTTESTIOKS.— What  is  said  of  the  importance  and  distribution  of  oxygen?  What  infer- 
ence has  been  drawn  from  the  composition  of  meteoric  stones  ?  How  is  oxygen  generally 
procured  ?  By  what  simple  method  may  a  small  quantity  of  oxygen  be  obtained  ? 


186 


INORGANIC    CHEMISTRY. 


FIG.  79. 


forated  cork  into  the  mouth,  of  the  generating  tube,  and  the  other  end  is  con- 
ducted into  a  vessel  filled  with  water.     The  apparatus  thus  arranged  may  be 

supported  by  means  of  a  piece 
of  cord  or  wire,  or  by  a  sort  of 
wooden  vice  (retort  holder)  con- 
structed for  chemical  purposes, 
and  represented  in  Fig.  79.  The 
oxygen  escaping  in  bubbles  from 
the  end  of  the  tube  under  water 
is  collected  in  a  glass  bottle  or 
jar,  which  has  been  previously 
i  filled  with  water  and  inverted 
in  the  vessel  j  care  being  taken 
either  to  close  the  mouth  of  the 
jar,  or  else  keep  it  continuously 
under  water  during  the  act  of 
inversion.  No  water  will  escape 
from  the  jar  until  bubbles  of  gas 
from  the  tube  are  passed  into  it ; 
but  when  this  is  permitted,  the 
gas,  by  reason  of  its  superior  levity,  ascends  and  displaces  the  water.  As 
soon  as  one  jar  is  filled  it  may  be  removed,  and  its  mouth  closed  with  a  cork, 
or  kept  below  the  water  level,  and  another  substituted  in  its  place.  (See 
Fig.  79.) 

For  the  production  of  oxygen  gas  in  considerable  quantity,  materials  less 
expensive  than  the  red  oxyd  of  mercury  are  used.  The  most  convenient,  and 
under  ordinary  circumstances  the  most  economical  method  which  can  be 
adopted  is,  to  expose  to  heat  in  a  retort,  or  flask  furnished  with  a  bent  tube, 
a  perfectly  dry  mixture  of  equal  parts  of  chlorate  of  potash  and  black  oxyd 
of  manganese.  A  common  Florence  flask  will  serve  for  this  purpose,  but  a 
flask  constructed  of  sheet  copper  and  fitted  with  a  small  lead  tube  and  screw- 
cap,  is  preferable.*  A  spirit-lamp  affords  sufficient  heat  to  effect  the  chem- 
ical decomposition,  and  the  gas  liberated  is  collected  in  the  manner  before 
described.  The  salt  chlorate  of  potash  is  very  rich  in  oxygen — every  124 
parts  of  it  by  weight  containing  48  parts  of  this  element  united  in  the  solid 
form  with  36  parts  of  chlorine  and  40  of  the  metal  potassium.  On  the  appli- 


*  Flasks,  or  generating  bottles  constructed  of  thin  sheet  copper,  and  furnished  with  a 
small  leaden  tube  and  a  screw-cup,  may  be  purchased  of  dealers  in  chemical  apparatus,  or 
can  be  easily  manufactured  by  a  coppersmith.  For  a  continuous  course  of  experiments 
their  employment  is  strongly  recommended,  as  they  obviate  entirely  the  annoyance  and 
trouble  arising  from  the  fracture  of  glass,  and  the  adjustment  and  preparation  of  tho 
tubes. 


QUESTIONS. — What  is  the  most  convenient  and  economical  method  of  obtaining  oxygen 
in  moderate  quantities  ?  Describe  the  method  of  obtaining  oxygen  from  chlorate  of  pot- 
ash? 


OXYGEN.  187 

cation  of  heat,  all  this  oxygen  is  driven  off  in  a  gaseous  state,  and  chlorine, 
united  with  potassium,  forming  the  chloride  of  potassium,  remains.  The  re- 
action may  be  represented  as  follows : — 

35  +  40  +  39+8-35  +  39+48-124 
<J1     Os   K    O-C1     K  +  Oo. 

Chlorate  of  potash  and  black  oxyd  of  manganese  both  yield  oxygen  when 
heated  separately,  but  under  the  conditions  of  heat  and  mixture  above  speci- 
fied, the  chlorate  of  potash  alone  disengages  oxygen.  The  manganese,  how- 
ever, without  taking  any  part  in  the  chemical  decomposition,  exercises  an 
important  influence  on  the  process,  apparently  by  its  mere  presence,  causing 
the  oxygen  to  be  liberated  with  the  utmost  facility  and  regularity,  and  at  a  • 
much  lower  temperature  than  when  the  chlorate  is  used  alone.  The  action 
of  the  manganese  in  producing  this  effect  has  been  explained,  by  suppos- 
ing that  it  mechanically  separates  the  particles  of  the  salt,  and  thus  dis- 
tributes the  heat  uniformly ;  but  if  this  is  true,  clean  sand,  powdered  glass, 
or  any  other  similar  material,  ought  to  act  equally  well,  which  is  not  the 
case. 

"When  very  large  quantities  of  FIG.  80. 

oxygen  are  required,  and  perfect 
purity  of  product  is  not  essential,  an 
economical  plan  is  generally  adopt- 
ed of  heating  the  black,  or  peroxyd 
of  manganese  to  redness  in  an  iron 
retort,  arranged  in  a  suitable  fur- 
nace. (See  Fig.  80.)  One  pound 
of  good  oxyd  of  manganese  thus 
heated,  will  yield  seven  gallons  of 
oxygen,  with  some  carbonic  acid.  This  last  may  be  entirely  removed  by 
causing  the  gas  to  pass  through  a  solution  of  potash.  In  this  process  MnO2 
becomes  converted  in  MnO-{-0. 

Oxygen  may  be  obtained  from  various  other  substances,  but  those  already 
mentioned  are  the  best,  and  the  most  frequently  employed.*  Red  lead  (oxyd 
of  lead),  and  likewise  saltpetre,  when  heated  strongly,  will  furnish  this 


*  A  new  method  of  preparing  oxygen  on  an  extensive  scale  for  economic  purposes,  has 
recently  been  proposed  by  M.  Boussingault.  He  states  that  caustic  baryta,  when  heated  to 
a  particular  temperature  in  the  free  presence  of  air,  absorbs  oxygen,  and  becomes  per- 
oxyd of  barium,  but  on  increasing  the  heat,  the  oxygen  absorbed  is  given  up.  Thus  the 
same  quantity  of  baryta  may  be  made  to  alternately  absorb  oxygen  and  evolve  it  into  a 
reservoir. 


QUESTIONS. — How  much  oxygen  does  this  substance  contain  *  "What  is  the  chemical 
reaction  in  this  process  ?  What  is  the  object  of  mixing  manganese  with  chlorate  of  pot- 
ash ?  Is  the  action  of  the  manganese  understood  ?  When  large  quantities  of  oxygen  are 
required,  what  method  is  adopted  ?  What  is  the  chemical  reaction  in  this  process  ?  From 
what  other  sources  may  oxygen  be  obtained  ? 


188  INORGANIC    CHEMISTRY. 

gas.  A  mixture  of  strong  sulphuric  acid  and  one  half  its  weight  of  black 
oxyd  of  manganese,  or  bichromate  of  potash,  will  liberate  oxygen  when 
heated. 

All  the  green  parts  of  plants  evolve  oxygen  when  exposed  to  the  light  of 
the  sun.  This  fact  may  be  readily  demonstrated-  by  placing  a  leafy  branch, 
which  is  still  connected  with  the  parent  plant,  or  a  number  of  fresh  leaves, 
under  ajar  filled  with  water,  and  then  exposing  them  to  the  influence  of 
solar  light.  After  a  short  time  smaii  air-bubbles,  consisting  of  pure  oxygen, 
will  collect  in  the  upper  part  of  the  vessel.  The  minute  bubbles,  also,  which 
may  be  often  seen  adhering  to  the  leaves  of  aquatic  plants  under  water,  are 
generally  pure  oxygen. 

282.  Properties  of  Oxygen . — Oxygen,  when  pure,  can  not  be 
distinguished  from  atmospheric  air,  being  colorless,  tasteless,  and,  under  or- 
dinary circumstances,  destitute  of  odor.  It  is,  however,  somewhat  heavier 
than  atmospheric  air ;  the  density  of  the  latter  being  represented  by  1-00, 
that  of  oxygen  would  be  MO. 

One  hundred  cubic  inches  of  dry  oxygen  weigh  34'20  grains.  In  its  sepa- 
rate condition  it  is  known  only  as  a  gas,  all  attempts  to  reduce  it,  by  im- 
mense pressure  and  extreme  low  temperature  acting  conjointly,  into  a  solid, 
or  even  liquid  condition,  having  failed.  Yet  the  learner  will  not  fail  to  per- 
ceive, that  oxygen  when  locked  up  in  combination  with  the  solid  substances 
from  whence  we  obtain  it,  must  be  itself  a  solid ;  and  this  consideration  en- 
ables us  to  form  some  conception  of  the  enormous  force  which,  under  the 
name  of  affinity,  is  capable  of  producing  this  effect. 

Oxygen  is  very  slightly  soluble  in  water ;  a  hundred  volumes  of  this  fluid, 
•  at  ordinary  temperatures,  dissolving  only  four  and  one  half  volumes  of  the 
gas.  Oxygen  possesses  a  wider  range  of  affinities  than  any  other  known 
substance,  and  combines  in  one  or  more  proportions  with  all  the  elements 
except  fluorine.  The  act  of  union  of  a  substance  with  oxygen  is  termed 
oxydation,  and  the  product  of  the  union  is  called  an  oxyd.  Oxyds  are  classi- 
fied and  divided,  as  has  been  before  shown  (§  265),  into  acids,  bases,  alkalies, 
etc. 

The  tendency  of  oxygen  to  unite  with  other  substances  varies  according  to 
the  circumstances  under  which  the  latter  are  presented  to  it,  being  greater 
under  the  influence  of  heat  than  of  cold,  and  greater  where  there  is  an  ex- 
cess than  where  there  is  a  deficiency  of  oxygen.  Oxygen,  at  ordinary 
temperatures,  enters  slowly  into  combination  with  most  of  the  metals.  This 
action  takes  place  much  more  rapidly  in  a  moist  than  in  a  dry  atmosphere. 
A  bar  of  polished  iron,  in  perfectly  dry  air  at  the  ordinary  temperature,  will 

QUESTIONS. — Do  plants  evolve  oxygen  ?  What  experiment  proves  this  ?  What  are  the 
properties  of  oxygen  ?  Has  oxygen  ever  been  condensed  into  a  liquid  or  solid  substance  ? 
Is  it  known  to  exist  in  either  of  the  latter  conditions?  What  is  said  of  its  solubility  in 
water  ?  Of  its  range  of  affinity  ?  What  are  the  products  of  the  union  of  oxygen  with 
other  substances  called  ?  How  does  the  tendency  of  oxygen  to  unite  with  other  sub- 
stances vary  ?  What  is  said  of  the  oxydation  of  the  metals  ?  Will  iron  rust  in  dry  air  at 
ordinary  temperatures? 


OXYGEN.  189 

remain  unchanged  for  any  length  of  time,  but  if  moisture  be  present,  it 
quickly  becomes  rusty.  In  the  case  of  iron,  the  oxydation  once  commenced 
will  spread  through  the  entire  mass  of  the  metal ;  but  in  other  instances,  as 
in  the  case  of  lead  and  zinc,  a  superficial  coat  of  the  oxyd  is  formed,  which 
adheres  firmly  to  the  surface,  and  protects  the  metal  beneath  from  further 
change, 

In  order  to  commence  and  carry  on  oxydation,  it  is  generally  necessary  to 
apply  heat.  An  iron  bar,  when  heated  red  hot,  and  exposed  to  the  oxygen 
of  the  air,  will  rapidly  become  covered  with  a  scale  of  oxyd,  or  rust.  A  stick 
of  charcoal  may  be  kept  in  oxygen  at  common  temperatures  for  years  with- 
out entering  into  combination  with  the  gas,  but  the  smallest  spark  upon 
the  surface  of  the  coal  will  cause  the  two  elements  to  unite  with  great 
rapidity. 

The  direct  union  of  oxygen  with  a  substance  is  always 
attended  with  an  evolution  of  heat. 

In  the  ordinary  rusting  of  iron,  the  disengagement  of  heat  is  too  slow  and 
feeble  to  be  readily  perceptible ;  but  in  some  instances,  where  the  union  with 
oxygen  at  ordinary  temperatures  is  rapid,  the  heat  accumulates,  and  often- 
times rises  sufficiently  high  to  cause  the  materials  to  burst  into  a  flame,  pro- 
ducing what  are  caltea  cases  of  "  spontaneous  combustion."  This  phenomenon 
is  often  exhibited  when  tow,  "  cotton- waste,"  or  other  fibrous  materials  that 
have  been  used  in  lubricating  machinery,  are  laid  aside  in  heaps.  The  oil 
upon  them  being  spread  over  a  large  surface,  absorbs  oxygen  with  great  rap- 
idity, and  the  temperature  of  the  mass  continues  to  increase  until  the  whole 
bursts  into  flame.  Charcoal,  reduced  to  a  fine  powder  and  exposed  to  the 
air,  moist  hay  in  stacks,  and  damp  cloths  in  bales,  frequently  take  fire  under 
the  same  circumstances. 

When  the  direct  union  of  oxygen  with  a  substance  is 
attended  with  an  evolution  of  both  light  and  heat,  the 
process  is  called  Combustion,  and  the  body  is  said  to 
burn.  On  the  other  hand,  the  body  which  can  combine 
with  oxygen  under  such  circumstances,  is  termed  a  Com- 
bustible, and  the  oxygen  a  supporter  of  combustion. 

All  the  ordinary  forms  of  combustion  are  simply  processes  of  oxydation, 
and  are  accompanied  by  a  withdrawal  of  free  oxygen  from  the  surrounding 
air ;  and  in  most  instances  the  oxydation  is  commenced,  or,  as  we  express  it, 
*'  the  fire  is  kindled,"  by  the  application  of  some  ignited  substance,  which 
raises  the  temperature  of  the  combustible  body  sufficiently  to  enable  it  to  at- 

QUESTIONS. — In  order  to  commence  and  carry  on  oxydation,  what  is  generally  neces- 
sary ?  What  are  examples  ?  What  phenomenon  always  accompanies  the  direct  union  of 
oxygen  with  a  substance  ?  What  is  spontaneous  combustion  ?  Give  examples.  What 
do  you  understand  by  the  ordinary  meaning  of  the  term  combustion  ?  What  is  a  combus- 
tible body?  Why  is  it  generally  necessary  to  apply  heat  in  order  to  cause  combustion  to 
commence  ? 


190 


INORGANIC     CHEMISTRY. 


tract  the  oxygen  of  the  air,  or  commence  burning;  afterward,  the  heat  which 
is  liberated  during  the  process  is  more  than  sufficient  to  carry  it  on,  and  thus 
the  combination  of  one  portion  of  oxygen  with  a  burning  body,  causes  the 
absorption  of  another  portion.* 

Bodies  which  will  burn  in  the  air,  together  with  many  substances  which 
are  generally  considered  as  incombustible,  burn  in  oxygen  gas  with  great 
splendor.  Experiments  illustrative  of  these  facts  are  among  the  most  bril- 
liant and  interesting  in  the  whole  science  of  chemistry. 

FIG.  81  If  we  blow  out  a  lighted  candle  in  the  air,  the  wick  continues 

to  glow  for  a  few  moments,  but  the  flame  does  not  sponta- 
neously re-appear.  If,  on  the  contrary,  the  candle,  still  pre- 
senting some  incandescent  points,  be  plunged  into  a  receiver 
containing  oxygen  (see  Fig.  81),  it  inflames  instantly,  and 
burns  with  great  brilliancy.  This  experiment,  which  may  bo 
repeated  with  a  small  narrow  mouth  jar  of  oxygen  a  great  num- 
ber of  times,  is  characteristic  of  pure  oxygen,  and  is  the  princi- 
pal test  used  to  detect  its  presence. 

A  glowing  slip  of  wood  introduced  into  oxygen,  bursts  into 
flame  with  a  slight  detonation.  A  bit  of  charcoal  bark,  slightly  ignited,  at- 
tached to  a  wire  and  lowered  into  a  jar  of  oxygen,  burns  with  great  rapidity, 
sending  off  showers  of  brilliant  scintillations  in  all  directions.  If  a  moistened 
slip  of  litmus  paper  (§  266)  be  introduced  into  the  jar  after  the  combustion, 
it  immediately  turns  red,  a  change  not  affected  by  atmospheric  air,  or  pure 
oxygen ;  consequently  an  acid  gas  has  been  formed  from  the  charcoal  and  the 
oxygen,  which  is  called  carbonic  acid. 

The  combustion  of  iron  in  oxygen  constitutes  a 
most  beautiful  experiment.  For  this  purpose  a 
piece  of  fine  iron  wire,  or,  what  is  still  better,  a 
steel  watch-spring,  coiled  in  the  form  of  a  spiral 
(see  Fig.  82)  is  employed.  One  end  of  the  wire 
is  tipped  with  a  bit  of  sulphur,  or  tinder,  and  the 
other  attached  to  a  cork,  so  that  the  spiral  may 
hang  vertically.  The  sulphured  end  is  then  lighted, 
and  the  wire  suspended  in  a  jar  of  oxygen,  open 
at  the  bottom,  as  is  represented  in  the  figure,  sup- 
ported upon  an  earthenware  plate.  The  wire  burns 
with  an  intense  white  light,  the  oxyd  of  iron  formed 
darting  out  in  brilliant  corruscations  in  every  direc- ' 
tion.  Melted  globules  of  oxyd  occasionally  fall  off, 
of  so  elevated  a  temperature,  that  they  remain  red  hot  for  some  time  under 


FIG  82. 


For  a  particular  consideration  of  combustion,  see  Chapter  VII. 


QUESTIONS. — How  does  pure  oxygen  act  on  combustible  substances  ?    Explain  the  exper- 
iments detailed. 


OXYGEN. 


191 


the  surface  of  water,  and  fuse  deeply  into  the  substance  of  the  plate  or  glass 
upon  which  they  strike. 

The  light  produced  by  phosphorus  burned  in  FiG.  83. 

oxygen  is  too  brilliant  and  intense  to  be  en-* 
dured  by  the  eye  ;  and  the  jar,  during  combus- 
tion, becomes  filled  with  a  dense  white  vapor, — 
phosphoric  acid,  which  is  slowly  absorbed  by 
water.  (See  Fig.  83.)* 

Kindled    sulphur    burns  in   oxygen  with  a 
beautiful  blue  light. 

283.  Oxygen  and  Respiration,— 
Oxygen  is  necessary  to  respiration, 
and  is  constantly  taken  into  the 
lungs,  from  the  atmosphere,  in  the 
process  of  breathing.  No  animal  can  live  in  an  atmos- 
phere which  does  not  contain  a  certain  portion  of  uncom- 
bined  oxygen. 

Oxygen,  by  the  chemical  action  involved  in  the  process  of  respiration,  passes 
from  a  free  state  into  a  state  of  combination  with  other  substances,  and  thereby 
becomes  unfitted  for  the  further  support  of  animal  life.  If  a  bird  be  con- 
fined in  a  limited  portion  of  atmospheric  air,  it  will  at  first  feel  no  inconve- 
nience; but  as  a  portion  of  oxygen  is  withdrawn  from  a  free  state  at  each 
inspiration,  its  quantity  diminishes  rapidly,  so  that  respiration  soon  becomes 
laborious,  and  in  a  short  time  ceases  altogether.  Should  another  bird.be  then 
introduced  into  the  same  air,  it  will  be  almost  immediately  suffocated ;  or  if 
a  lighted  candle  be  immersed  in  it,  its  flame  will  be  extinguished.  Respira- 
tion and  combustion  both  produce  the  same  effect,  in  causing  free  oxygen  to 
be  removed,  or  absorbed  from  the  atmosphere.  An  animal  can  not  live  in 

*  This  experiment  should  be  performed  with  great  care  ;  otherwise  the  combustion-jar 
is  liable  to  be  broken,  and  the  burning,  liquid  phosphorus  dispersed  in  every  direction. 
The  combustion  ladle  should  be  deep — an  iron  cup  or  a  piece  of  chalk  scooped  out  and  at- 
tached to  a  wire,  the  whole  perfectly  dry.  The  phosphorus  should  be  divided  under 
water,  and  afterward  dried,  not  by  wiping,  but  by  contact  with  bibulous  paper.  It  should 
not  be  allowed  to  project  above  the  level  of  the  deflagrating  ladle,  because  during  the  act 
of  combustion  burning  particles  might  disperse  and  stick  against  the  sides  of  the  jar,  thus 
infallibly  causing  rupture  of  the  glass.  A  similar  result  might  be  occasioned  by  employ- 
ing wet  phosphorus,  the  aqueous  moisture  from  which,  by  expanding  into  steam,  would 
scatter  the  melted  phosphorus  in  all  directions.  One  other  point  should  be  particularly 
attended  to.  The  phosphorus  placed  in  the  ladle,  and  lowered  into  the  jar,  should  be  ig- 
nited on  the  surface  by  touching  it  with  a  hot  wire,  and  not  by  holding  the  whole  ladle 
over  a  flame.  These  directions  being  attended  to  will  insure  the  success  of  the  experi- 
ment, whereas  by  neglecting  them,  simple  though  they  may  appear,  or  any  one  of  them, 
failure  of  the  experiment  is  certain,  and  danger  imminent.— FABADAY. 

QUESTIONS.— Is  oxygen  necessary  to  respiration  ?  What  effect  has  the  process  of  respi- 
ration on  oxygen  ?  Illustrate  this.  What  analogy  is  there  between  respiration  and  com- 
bustion ? 


192  INORGANIC     CHEMISTRY. 

air  unfitted  to  support  combustion  ;  and,  under  all  ordinary  circumstances, 
combustion  will  not  continue  in  air  containing  too  little  oxygen  for  respira- 
tion. 

Fermentation  also  acts  like  respiration  and  combustion  in  absorbing  free 
oxygen  from  the  atmosphere. 

Although  oxygen,  as  a  constituent  of  the  atmosphere,  is  necessary  to  respi- 
ration, it  is  destructive  of  animal  life  when  breathed  for  any  considerable 
length  of  time  in  a  state  of  purity.  When  a  rabbit,  for  example,  is  immersed 
in  an  atmosphere  of  pure  oxygen,  it  at  first  experiences  no  inconvenience, 
but  after  an  interval  of  an  hour,  or  more,  an  unnatural  e-xcitement  of  the  sys- 
tem is  occasioned,  accompanied  by  a  rapid  respiration  and  circulation  of  the 
blood  ;  this  is  soon  followed  by  insensibility,  and  death  ensues  in  from  six  to 
ten  hours. 

284.  Magnetism    of   0  x  y  g  e  n.  —  Oxygen  is  highly  magnetic  ;  that 
is,  it  sustains  the  same  relations  in  degree  to  a  magnet,  that  iron  does.     It  has 
been  further  proved  that,  like  iron,  it  loses  its  magnetism  when  strongly 
heated,  but  recovers  it  when  the  temperature  falls.     Faraday  computes  the 
magnetic  effect  of  oxygen  in  the  air  to  be  equal  to  that  of  a  metallic  shell  of 
iron,  l-250th  of  an  inch  in  thickness  surrounding  the  globe  of  the  earth. 

285.  Oxygen    in    Combination  .  —  The  force  which  holds  oxygen 
in  combination  varies  extremely  in  different  substances.     In  silica,  (quartz, 
rock  crystal,  etc.),  nearly  one  half  the  entire  weight  of  which  is  oxygon,  it  is 
combined,  or  imprisoned,  so  to  speak,  with  such  force,  that  its  liberation  can 
only  be  effected  by  the  most  powerful  agencies  —  heat  alone  failing  to  produce 
the  slightest  effect.     In  other  solid  oxygenized  bodies,  however,  the  affinities 
are  so  nicely  balanced,  that  the  slightest  decomposing  cause  is  sufficient  to 
rend  the  elements,  as  we  may  say,  from  each  other,  and  set  the  oxygen  free. 
A  very  striking  instance  of  this  is  furnished  by  chlorate  of  potash,  the  sub- 
stance generally  employed  in  the  production  of  oxygen  —  every  124  parts  of 
which,  by  weight,  contain,  as  before  stated,  48  of  oxygen.     A  very  slight 
degree  of  heat  suffices  to  overcome  the  admirably  poised  balance  of  affinities, 
by  which  the  combined  elements  of  this  salt  are  held  together,  and  liberate 
every  particle  of  oxygen.     But  this  result  can  be  effected  by  other  agencies. 
For  example,  if  we  take  a  small  quantity  of  sulphur,  charcoal,  phosphorus, 
sulphuret  of  antimony,  or,  to  generalize,  any  other  solid  which  has  a  strong 
attraction  for  oxygen,  and  mix  either  of  them  with  a  little  chlorate  of  pot- 
ash, carefully  and  with  an  avoidance  of  friction,  the  compound  so  obtained, 
when  struck  with  a  hammer  upon  an  anvil,  will  explode  violently.     The  ex- 
periment is  best  conducted  by  folding  the  mixture  in  a  piece  of  paper.     With 
phosphorus  the  explosive  violence  is  greatest,  with  charcoal  least,  the  varia- 
tion being  indicative  of  the  respective  tendency  of  these  substances  to  com- 
bine with  oxygen  under  the  circumstances  of  the  experiment. 


QUESTIOTJB.  —  What  effect  does  oxygen  have  on  animal  life  when  breathed  pure  ?  What 
is  said  respecting  the  magnetism  of  oxygen  ?  Illustrate  the  various  conditions  under 
which  oxygen  exists  in  combination  '? 


OXYGEN.  193 

Gunpowder  is  another  example  of  a  substance  holding  a  large  amount  of 
oxygen  in  combination,  ready  to  spring  into  action  with  an  almost  irresistible 
violence. 

286.  Active  and  Passive  Condition  of  Oxygen . — Oxygen, 
as  hitherto  considered,  assumes  two  conditions,  or  states,  widely  different  from 
each  other.     These  may  be  termed  its  active  and  passive  conditions.     As 
locked  up  in  rock-crystal,  flint,  clay,  and  other  solids ;  as  constituting  eight 
ninths  of  the  bland  liquid,  water ;  as  an  uncombined  gas  in  the  atmosphere, 
it  is  quiescent,  inactive,  waiting — retaining,  however,  all  its  forces  in  a  latent 
state.     This  inactivity  is  one  extremity  of  the  scale  of  qualities  possessed  by 
oxygen.     Intense  violence  characterizes  its  other  extreme  condition — u  mani- 
fested," says  Professor  Faraday,  "  with  tremendous  energy  in  the  phenomena 
of  combustion  and  explosion — rushing  with  violence  into  other  forms — dis- 
playing the  most  glorious  exhibitions  of  light  and  heat — generating  combina- 
tions of  characters  diametrically  opposed,  from  the  extreme  of  alkalinity  on 
the  one  hand,  to  the  most  violent  acidity  on  the  other,  and  finally,  having 
gone  through  its  metamorphic  phasos,  assuming  its  appointed  place  of  rest  in 
the  world's  economy." 

287.  Ozone  . — In  addition  to  these  two  extreme  conditions,  oxygen  may 
assume  another,  in  some  respects  stiU  more  extraordinary ; — a  state  in  which 
it  is  neither  fully  active  or  fully  passive,  but  intermediate  between  the  two 
former  conditions — a  state  in  which  the  activity  possessed  is  not  only  less  in 
amount,  but  different  in  quality.     This  condition  of  oxygen  is  characterized 
by  the  name  of  Ozone. 

It  has  long  been  noticed  that  the  working  of  an  electric  machine,  espe- 
cially in  a  close  apartment,  was  accompanied  by  a  peculiarinlphur-like  odor, 
and  also,  that  a  similar  odor  pertained  for  some  little  time  to  places  that  had 
been  struck  by  lightning.  Beside  recognizing  these  facts,  and  designating  the 
odor  in  question  as  "  the  electric  smell"  no  explanation  of  the  phenomenon 
was  attempted  by  scientific  men  until  within  a  very  recent  period;  (since  1840). 
It  was  at  last  noticed,  almost  accidentally,  that  if  a  piece  of  paper  moistened 
with  a  solution  of  starch,  and  a  peculiar  compound  of  iodine  (iodide  of  potas- 
sium), was  exposed  in  places  pervaded  by  this  odor,  it  was  speedily  turned 
blue.  Now,  this  turning  blue  is  an  indication  of  the  liberation  of  iodine  from 
its  combination ;  and  the  liberation  of  iodine  is  an  indication  of  the  agency 
of  oxygen;  so  that  in  the  determination  of  this  additional  fact,  a  connection 
was  established  between  oxygen  in  an  active  state  and — the  electric  smelL 

The  germ  of  knowledge  thus  obtained  was  expanded  and  generalized  by 
Professor  Schonbein  of  Bale,  who  showed,  by  carefully  conducted  experi- 
ments, that  the  same  smell  and  its  corresponding  action  might  be  generated 
at  pleasure,  by  various  means — that  the  agent  producing  the  odor  occasioned 
other  effects  beside  that  of  affecting  the  starch  paper,  such  as  bleaching,  de- 

QUESTKXNB — Under  what  two  conditions  does  oxygen  generally  manifest  itself  ?  What 
is  the  third  condition  of  oxygen  ?  What  is  this  condition  termed  ?  What  circumstances 
led  to  the  discovery  of  ozone  ?  What  discoveries  were  made  by  Schonbein  ? 

9 


194 


INORGANIC    CHEMISTRY. 


odorizing,  and  corroding — and  finally,  that  the  mysterious  gaseous  agency 
itself  was  neither  more  nor  less  than  oxygen — oxygen  gas  existing  iu  a 
marked  condition,  or,  as  it  is  termed,  in  its  aliotropic  form. — FARADAY. 

Preparation . — Ozone  may  bo  obtained  by  passing  a  succession  of 
electric  sparks  through  a  tube  or  vessel  containing  atmospheric  air,-  or  pure 
oxygen  gas.  It  is  also  produced  by  the  slo\v  action  of  phosphorus  upon  oxy- 
gen, or  atmospheric  air.  This  latter  reaction  may  bo  readily  demonstrated 
as  follows : 

Take  a  quart  glass  bottle,  and  place  in  it  a  little  water  and  a  stick  of 
phosphorus,  first  demonstrating  the  absence  of  ozone  by  testing  it  with 
iodine-starch  paper.*  Close  the  bottle,  and  allow  the  whole  to  remain  for 
a  little  time.  On  again  immersing  the  paper  slip,  it  changes  color,  assum- 
ing a  tint  of  blue.  This  result  is  not  due  to  the  vapors  of  phosphoric 
acid  which  may  be  noticed  in  the  bottle,  as  they  are  readily  absorbed  by 
passing  the  gaseous  contents  of  the  bottle  through  water,  while  the  ozone  re- 
mains unaltered. 

The  formation  of  ozone  may  be  also  shown  by  another  process  still  more 


FiG.  84. 


simple.  Take  a  glass  jar,  and  first  demonstrate 
by  the  iodine-starch  paper  the  absence  of  ozone. 
Then  pour  into  the  jar  a  little  ether,  and  there 
is  still  no  ozone ;  but  if  we  heat  a  glass  rod  in 
the  flame  of  a  spirit-lamp,  and  immerse  it  moder- 
ately hot  (see  Fig.  84),  ozone  will  be  abundantly 
produced. 

Properties . — Ozono  has  never  been  ob- 
tained in  a  separate  state,  arid  appears  to  bo 
entirely  insoluble  in  all  liquids.  It  has  a  pecu- 
liar odor,  whilst  ordinary  oxygen  is  totally  devoid 
of  all  smell.  It  possesses  powerful  blcaciiing 
properties,  and  if  a  solution  of  sulphate  of  indigo 
be  poured  into  a  vessel  containing  ozone,  its 
deep  blue  color  is  destroyed  with  great  rapidity. 
If  the  same  experiment  be  tried  with  common 

oxygen,  no  bleaching  action  takes  place.  Ozono  also  exercises  a  remarkable 
influence  over  certain  odors ;  thus,  if  a  piece  of  tainted  meat  be  immersed  in 
this  gas  (see  Fig.  85)  the  effluvium  is  instantly  destroyed. 

Ozone  is  perhaps  the  most  powerful  of  all  oxydizing  agents.  It  corrodes 
even  organic  bodies,  such  as  cork  and  India-rubber,  while  fragments  of  iron, 
«opper,  etc.,  rapidly  absorb  it,  and  become  converted  into  oxyds.  Silver, 


*  Iodine  starch  paper  ma7  be  simply  prepared  by  mixing  a  little  starch  with  a  solution 
of  iodide  of  potassium — a  salt  obtained  of  any  druggist — and  imbuing  unsized  paper  with 
the  compound. 


QUESTIONS.— How  may  ozone  be  obtained  ?    What  are  the  properties  of  ozona  ?    What 
1*  said  of  the  oxydizing  influences  of  ozone  ? 


OXYGEN. 


195 


FIG.  85. 


•under  ordinary  circumstances,  is  not 
affected  by  oxygen,  and  has  hence 
been  considered  as  one  of  the  noble 
metals ;  but  if  a  piece  of  silver-foil, 
moistened  with  water,  be  plunged 
into  ozone,  it  rapidly  crumbles  into 
dust — oxyd  of  silver.  Ozone  dis- 
places iodine  from  its  combinations 
with  the  metals,  setting  the  iodine 
free.  This  reaction  is  so  easily  pro- 
duced, and  is  so  sensitive,  that  it  fur- 
nishes the  readiest  and  most  delicate 
method  of  detecting  the  presence  of 
traces  of  ozone  in  the  air.  A  slip  of 
paper,  as  before  stated,  moistened  with 
starch  and  iodide  of  potassium,  and 
inserted  in  a  vessel  containing  the 
slightest  admixture  of  ozone,  becomes 
blue  from  the  action  of  the  liberated  iodine,  which  immediately  unites  with 
the  starch,  and  forms  the  blue  iodide  of  starch. 

One  of  the  most  singular  circumstances  connected  with  ozone  is  the  effect 
of  heat  upon  it.  A  temperature  not  much  higher  than  boiling  water  is  suf- 
ficient to  destroy  it  entirely.  Advantage  is  taken  of  this  fact  to  demonstrate 
the  absolute  chemical  identity  of  ozone  and  oxygen.  Ozone  passed  into  one 
end  of  a  red  hot  tube  comes  out  ordinary  oxygen  at  the  other  end.* 


*  Respecting  this  strange  condition  of  allotropism,  of  which  ozone  is  a  particular  ex- 
ample, Professor  Faraday,  in  a  recent  publication,  remarks : — "  There  was  a  time,  and 
that  not  long  ago,  when  it  was  held  among  the  fundamental  doctrines  of  chemistry,  that 
the  same  body  always  manifested  the  same  chemical  qualities,  excepting  only  such  va- 
riations as  might  be  due  to  the  three  conditions  of  solid,  liquid,  and  gas.  This  was  held 
to  he  a  canon  of  chemical  philosophy  as  distinguished  from  alchemy  ;  and  a  belief  in  the 
possibility  of  transmutation  was  held  to  be  impossible,  because  at  variance  with  this  fun- 
damental tenet.  But  we  are  now  conversant  with  many  examples  of  the  contrary ;  and, 
strange  to  say,  no  less  than  four  of  the  non-metallic  elements,  namely,  oxygen,  sulphur, 
phosphorus,  and  carbon,  are  subject  to  this  modification.  The  train  of  speculation  which 
this  contemplation  awakens  within  us  is  extraordinary.  If  the  condition  of  allotropism 
were  alone  confined  to  compound  bodies,  that  is  to  say,  bodies  made  up  of  two  or  more 
elements,  we  might  easily  frame  a  plausible  hypothesis  to  account  for  it ;  we  might  as- 
sume that  some  variations  had  taken  place  in  the  arrangement  of  their  particles.  But 
when  a  simple  body,  such  as  oxygen,  is  concerned,  this  kind  of  hypothesis  is  no  longer 
open  to  us ;  we  have  only  one  kind  of  particle  to  deal  with,  and  the  theory  of  altered 
position  is  no  longer  applicable.  In  short,  it  does  not  seem  possible  to  imagine  a  rational  » 
hypothesis  to  explain  the  condition  of  allotropism  as  regards  simple  bodies.  We  can  only 
accept  it  as  a  fact,  not  to  be  doubted,  and  add  the  discovery  to  that  long  list  of  truths 
which  start  up  in  the  field  of  every  science,  in  opposition  to  our  most  cherished  theories 
and  long-received  convictions." 


QTTESTIONS.— -What  reaction  takes  place  when  ozone  turns  iodine-starch  paper  blue  ? 
What  effect  has  heat  upon  ozone  ?    How  is  ozone  proved  to  be  simply  modified  oxygen  ? 


196  INORGANIC     CHEMISTRY. 

Ozone  may  be  generally  recognized  in  air  which  has  swept  over  the  ocean, 
although  generally  absent  in  air  which  has  swept  over  land  It  would  ap- 
pear that  a  moist  state  of  the  atmosphere  is  necessary  to  its  development.* 
Mr.  Wise,  the  celebrated  aeronaut  states,  that  when  on  one  occasion  during 
an  ascension,  he  became  enveloped  in  a  thunder-cloud,  he  found  the  surround- 
ing air  most  powerfully  impregnated  with  the  peculiar  odor  of  ozone. 

It  can  not  be  doubted  that  so  active  an  agent  as  ozone  present  in  the  at- 
mosphere, must  exercise  an  important  influence  in  the  economy  of  nature. 
What  this  influence  is,  is  not  definitely  known.  There  can  be  but  little 
doubt,  however,  that  it  acts  as  a  purifying  agent — oxydizing  or  burning  up 
noxious  products  floating  in  the  atmosphere.  This  supposition  coincides  with 
the  opinion  extensively  entertained,  that  when  ozone  is  in  excess  in  the  air, 
diseases  of  the  lungs,  influenza^  etc.,  prevail  (as  would  be  expected  from  its 
irritating  character)  :  and  that  when  it  is  deficient,  fevers,  etc.,  are  common. 
Observers  generally  agree,  that  during  those  seasons  in  which  cholera  rages, 
the  quantity  of  ozone  in  the  atmosphere  is  greatly  diminished. 

288.  Daily    Consumption   of  Oxygen . — "  It  is  not  easy,"  says 
Professor  Faraday,  "to  form  an  adequate  idea  of  the  aggregate  results  ac- 
complished by  oxygen  in  the  economy  of  the  world.     For  the  respiration  of 
human  beings  alone,  it  has  been  calculated  that  no  less  than  one  thousand 
millions  of  pounds  of  oxygen  are  daily  required,  and  for  the  respiration  of  ani- 
mals double  that  quantity  ;  whilst  the  processes  of  combustion,  fermentation, 
decay,  and  the  like,  continually  going  on,  increase  the  daily  sum  total  to  eight 
thousand  millions  of  pounds.     Reduced  to  tons,  we  have  the  figures  7,142,847 
as  representing  the  daily  consumption,  and  2,609,285,714  the  yearly  consump- 
tion.    Taken  in  connection  with  theSe  statements,  the  fact  that  from  one  half 
to  two  thirds  of  the  bulk  of  all  the  matter  upon  our  planet  consists  of  oxygen, 
does  not  seem  wonderful. 

SECTION    II. 

MANAGEMENT     OP    GASES. 

289.  Pneumatic    Trough  , —  For  collecting  gases  not  absorbed  to 
any  considerable  extent  by  water,  an  arrangement,  known  as  the  Pneumatic 
Trough,  is  always  employed.   For  small  operations  this  apparatus  may  bo  simply 
constructed  by  fixing  a  perforated  shelf  within  a  shallow  dish,  or  wooden  tub, 
in  such  a  way,  that  when  the  vessel  is  filled  with  water  to  the  proper  height, 


*  Prof.  Smallwood,  of  Montreal,  in  a  communication  to  the  American  Association  for 
the  Advancement  of  Science,  in  1S57,  stated  that  during  the  seven  years  ending  i:i  1856, 
there  were  at  Montreal,  913  days  on  which  rain  and  snow  fell ;  and  during  the  like  period, 
there  were  81C  days  on  which  ozone  was  present  in  the  air  ia  appreciahle  quantity. 


QUESTIONS. — Under  what  circumstances  is  ozone  noticed  in  the  atmosphere?  What 
influence  is  ozone  supposed  to  have  in  the  economy  of  nature?  What  is  said  respecting 
the  daily  consumption  of  oxygen  ?  How  are  gases  not  absorbed  by  water  collected  ?  De- 
scribe the  pneumatic  trough. 


MANAGEMENT     OF     GASES. 


197 


FIG.  86. 


the  shelf  will  be  covered  by  it  to  the  depth  of  about 
an  inch.  (See  Fig.  86.)  Another  and  more  elegant 
arrangement,  constructed  of  glass,  and  suitable  for 
a  lecture  table,  is  represented  by  Fig.  87.  The 
vessel  intended  for  the  reception  of  gas  is  filled  with 
water,  inverted  and  placed  upon  the  shelf  of  the 
pneumatic  trough,  with  its  mouth  directly  over  the 
perforation  in  it.  The  extremity  of  the  gas-delivering 

tube,  which  dips  into  the  water, 
is  brought  directly  beneath  the 
shelf,  in  such  a  way  that  the 
bubbles  of  gas  escaping,  ascend 
through  the  opening  in  the  shelf 
into  the  vessel  above. 

For  permanent  use,  the  pneu- 
matic trough  is  usually  construct- 
ed on  a  larger  scale,  of  copper  or 
tin  plate,  or  of  wood,  and  fur- 
nished with  perforated  shelves, 
arranged  below  the  water  level, 
of  sufficient  extent  to  accommo- 
date a  number  of  gas  receivers  at  the  same  time.  Fig.  88  represents  the  con- 
struction of  such  a  pneumatic  trough. 

Water  is  supported  in 
the  gas-receivers  above 
the  level  of  the  pneu- 
matic trough  by  reason 
of  the  pressure  of  the 
atmosphere,  on  the 
same  principle  as  mer- 
cury is  sustained  in  the 
tube  of  a  barometer. 

In  the  collection  of 
gases  over  the  pneu- 
matic trough,  it  should 
be  observed  that  the 

gas  which  first  comes  over  is  mixed  with  the  atmospheric  air  of  the  generating 
vessel,  or  retort;  hence  a  volume  of  gas  equal  to  about  twice  the  volume  of 
the  retort  should  be  allowed  to  escape,  as  impure.  This  precaution  is  espe- 
cially to  be  attended  to  in  the  case  of  gases  (such  as  hydrogen)  which  form 
explosive  mixtures  with  atmospheric  air.  Gases  may  be  transferred  from  one 
vessel  to  another,  over  the  pneumatic  trough,  with  the  utmost  facility,  by 
first  filling  the  vessel  into  which  the  gas  is  to  be  passed  with  water,  inverting 
it,  carefully  retaining  its  mouth  below  the  water-level,  and  then  bringing 

QUESTIONS. — "What  precaution  should  he  ohserved  in  collecting  gases  over  a  pneumatic 
trough  ?    How  may  gases  be  transferred  from  one  vessel  to  another  ? 


FlG.  88. 


198 


INORGANIC     CHEMISTRY. 


FIG.  89. 


beneath  it  the  mouth  of  the  ves- 
sel containing  the  gas.  (See  Fig. 
89.)  On  gently  inclining  the 
latter,  the  gas  passes  into  the 
second  vessel. 

Ajar,  wholly  or  partially  filled 
with  gas  at  the  pneumatic  trough, 
may  be  removed  by  placing  be- 
neath it  a  common  plate,  deep 
enough    to     contain     sufficient 
water  to  cover  the  edges  of  the  jar. 
In  this  way  gas,  especially  oxy- 
gen, may  be  preserved  for  a  con- 
siderable length  of  time  without 
admixture  with  the  external  air. 
290.    Gasometers. — In  order  to  collect  and  preserve  large  quantities 
of  gas,  and  to  experiment  with  them  more  conveniently,  capacious  vessels  of 
sheet-iron,  or  copper,  called  gasometers,  are  used.     They  consist  in  general 


PIG.  90. 


of  a  cylindrical  reservoir,  suspended 
with  its  mouth  downward,  and  fit- 
ting into  an  exterior  and  larger  cyl- 
indrical vessel,  or  cistern,  filled  with 
water,  as  is  shown  in  Fig.  90,  which 
represents  a  pair  of  gasometers.  The 
inner  cylinder  moves  freely  in  the 
outer  one,  rising  and  falling  as  the 
gas  is  forced  in  or  pressed  out.  The 
posts  on  each  side  of  the  cylinder 
are  hollow,  and  contain  weights, 
suspended  to  and  balancing  the  in- 
ner moveable  cylinder,  so  that  it 
only  presses  on  the  gas  as  required. 
An  upright  rod  of  metal,  shown  in 
the  engraving,  rising  from  the  inner 
cylinder,  and  passing  through  the 
supporting  frame-work,  keeps  the 
cylinder  steady  in  its  place,  as  it 
rises  or  falls.  Pressure,  for  forcing 
out  the  gas,  is  obtained  by  slipping 
on  to  this  rod  slit- weights  of  iron,  as 
is  seen  in  the  figure.  Gas  is  introduced  into,  and  discharged  from  the  gas- 
ometer, by  means  of  a  metal  pipe,  furnished  with  stop-cocks,  and  entering  at 
the  bottom  of  the  stationary  cylinder.  For  convenience,  this  pipe  is  carried 
up  in  front  of  the  gasometer  on  the  outside  (as  seen  in  the  engraving),  and  by 


QUESTIONS— What  are  gasometers  ?    How  are  they  constructed  ? 


HYDROGEN.  199 

means  of  flexible  tubes  of  India-rubber  or  gutta-percha,  which  screw  on  to  its 
extremity,  the  gas  can  be  conducted  to  any  distances  and  in  any  direction. 

The  stop  cocks  seen  at  the  bottom  of  the  gasometer  are  for  the  purpose  of 
letting  off  the  water,  whenever  this  becomes  necessary. 

The  large  gasometers  used  for  the  collection  and  storage  of  illuminating  gas 
are  constructed  upon  precisely  similar  principles.  Their  general  construction 
is  represented  in  Fig.  91.  The  gas  from  the  retorts  is  conducted  by  a  pipa 

FIG.  91. 


into  the  interior  of  the  gasometer,  and  elevates  it.  Another  pipe,  opening 
also  into  the  interior,  is  connected  with  the  service-pipes  which  supply  tho 
gas.  The  gasometer  is  balanced  by  counter  weights,  supported  by  chain?, 
which  pass  over  pulleys,  and  just  such  a  preponderance  is  allowed  to  it  as  13 
sufficient  to  give  the  enclosed  gas  the  compression  necessary  to  drive  it  through 
the  pipes  to  the  remotest  part  of  the  district  to  be  illuminated. 

SECTION     III. 

HYDROGEN. 

Equivalent  1.     Symbol  H.     Density  0*0692  (Air*- 1.) 

291.  History, — Hydrogen  was  first  correctly  described 
by  Cavendish,  an  English  chemist,  in  1766.  Before  this 
it  had  been  confounded  with  .several  of  its  compounds, 
under  the  designation  of  inflammable  air.  Its  name  is 
derived  from  vdwp,  water,  and  ye^vaw,  I  give  rise  to,  and 
refers  to  its  production  of  water  by  uniting  with  oxygen. 

QUESTIONS. — What  is  the  history  of  hydrogen  1    What  is  its  equivalent,  symbol,  and 


200 


INORGANIC    CHEMISTRY. 


292.  Natural  History  and  Distribution.— Hydrogen  is 
never  found  in  nature  in  a   free  state.     The  substance 
which  contains  it  in  the  greatest  abundance  is  water,  of 
which  it  forms  one  ninth  part  by  weight.     As  a  constituent 
of  other  inorganic  bodies,  it  is  not  very  abundant  in  nature, 
but  in  the  organic  kingdom  it  enters  largely  into  the  com- 
position of  most  animal  and  vegetable  substances. 

293.  Preparation. — -Hydrogen   is   always  obtained   for 
practical  or  experimental  purposes  from  the  decomposition 
of  water. 

It  is  liberated  in  the  state  of  greatest  purity  through  the  agency  of  the  vol- 


FIG.  92. 


o  . 


taic  current.  When  the  wires  connecting  the  poles 
of  a  galvanic  battery  in  action  are  caused  to  terminate 
in  water,  decomposition  is  occasioned — hydrogen 
being  evolved  at  the  negative  pole  and  oxygen  at  the 
positive.  (See  §  242,  p.  148.)  By  placing  tubes 
filled  with  water  over  the  respective  poles  (see  Fig. 
92)  the  two  gases  may  be  collected  in  a  separate 
state. 

Water  can  not,  under  all  ordinary  circumstances, 
be  decomposed  by  the  action  of  heat  alone.*    Hydro- 
^     gen  may,  however,  be  separated  from  water  by  heat- 
ing this  fluid  in  contact  with  substances  which  absorb  its  oxygen.     Thus,  if 
the  vapor  of  water  (steam)  is  passed  over  finely  divided  iron,  heated  to  bright 
redness,  the  water  is  decomposed,  oxygen  uniting  with  the  iron  to  form  oxyd 
of  iron,  and  hydrogen  being  set  free. 

us  experiment,  which  was  devised  by  Lavoisier,  hi  order  to  prove  that 
water  is  a    compound  substance,  is  pIG 

easily  performed  by  placing  a  quantity 
of  iron  filings  in  an  iron  tube  (a  gun- 
barrel,  or  better,  a  porcelain  tube, 
protected  by  a  covering  of  sheet-iron), 
arranged  in  a  furnace,  as  is  represent- 1« 
ed  in  Fig.  93 ;  one  end  of  the  tube  is 
connected  with  a  retort,  or  flask,  a, 
containing  a  small  quantity  of  water, 
from  which,  by  the  heat  obtained  from 


*  Mr.  Grove,  the  eminent  English  physicist,  has  recently  shown  that  the  vapor  of  water 
Is  decomposed  to  a  small  hut  sensible  extent  by  an  exceedingly  high  temperature,  and 
resolved  into  its  constituent  gases. 

QTTEBTIOXS.— -What  Is  said  of  its  natural  history  and  distribution  ?  How  is  hydrogen 
obtained?  What  process  yields  it  in  the  greatest  purity?  Under  what  circumstances 
can  water  be  decomposed  by  heat?  Describe  the  experiment  of  Lavoisier. 


HYDROGEN. 


201 


FIG,  94. 


a  spirit  lamp,  a  current  of  steam  is  driven  through  the  tube,  at  the  moment 
the  metal  has  attained  a  full  red-heat. 

If  the  conditions  of  this  experiment  are  reversed,  and  a  stream  of  hydrogen 
be  made  to  pass  over  oxyd  of  iron  heated  to  redness,  the  hydrogen  unites 
with  and  removes  the  oxygen  of  the  oxyd  of  iron,  thereby  leaving  metallic 
iron,  and  producing  water,  • 

If  we  sprinkle  water  in  small  quantity  upon  red-hot  coals,  a  portion  of  it 
Will  be  decomposed  on  the  same  principle  as  in  the  above  experiment  The 
oxygen  combines  with  the  carbon  and  increases  the  intensity  of  the  fire, 
while  the  liberated  hydrogen  burns  and  develops  a  very  high  degree  of  heat. 
Blacksmiths,  it  is  well  known,  are  accustomed  to  sprinkle  their  fires  with 
water,  in  order  tq  augment  the  heat,  and  too  little  Water  thrown  upon  a  confla- 
gration will  often  produce  more  injury  than  benefit. 

Some  of  the  metals,  such  as  potassium  and  sodium,  are  capable  of  decom- 
posing water  (combining  with  the  oxygen  and  liberating  hydrogen),  without 
the  aid  of  heat,  This  may  bo  shown  by  the  following  ex- 
periment : 

Fill  a  glass  tube  with  water,  from  which  the  air  has  been 
expelled  by  boiling,  and  invert  it  in  a  vessel  of  water.  Pass 
into  the  mouth  of  this  tube,  by  means  of  a  wire,  a  small 
piece  of  sodium,  as  is  represented  in  Fig,  93.  This  metal, 
being  lighter  than  water,  ascends  to  the  surface,  and  absorb- 
ing oxygen  from  the  water,  rapidly  liberates  hydrogen, 

Hydrogen  gas  is  most  conveniently  obtained  by  putting  pieces  of  fcino 
or  iron  into  oil  of  vitriol,  of  strong  sulphuric  acid,  diluted  with  six  or  eight 
times  its  bulk  of  water.  Practically,  this  process  may  be  conducted  as  fol- 
lows ; — Introduce  into  a  suitable  jar  or  bottle  a  small  quantity  of  sheet  zinc 

(or  in  the  absence  of  zinc,  scraps  of  iron, 
nails,  etc.)  cut  into  small  pieces,  together 
•with  water  sufficient  to  more  than  cover 
the  same.  Then  add  a  small  quantity  of 
Btrong  sulphuric  acid,  and  the  evolution  of 
gas  immediately  commences.  By  inserting 
into  the  opening  of  the  flask,  a  perforated 
cork,  to  which  a  bent  glass  tube  is  fitted 
(see  Fig.  96),  the  gas  is  easily  collected 
over  water  in  the  usual  way.  Particular 
care  should,  however,  be  taken  not  to  ad- 
mit the  gas  into  a  receiver,  until  all  the  at- 
mospheric air  in  the  flask  has  been  expelled, 
An  ounce  of  zinc  is  sufficient  to  liberate 
from  water  about  two  and  a  half  gallons  of 

QTTESTIOXS.— Why  does  a  blacksmith  sprinkle  his  fires  with  Water  ?  Do  any  of  the 
metals  decompose  water  without  the  aid  of  heat  ?  What  experiment  illustrates  this  fact  ? 
How  is  hydrogen  obtained  most  conveniently  ?  Describe  the  practical  performance  of  this 
process  ? 

9* 


FIG.  95. 


202  INORGANIC    CHEMISTRY. 

hydrogen,  and  the  evolution  of  the  gas  is  regulated  by  the  supply  of  acid.  By 
means  of  a  funnel-tube  fitted  into  the  cork  of  the  generating  vessel,  and  de- 
scending within  the  vessel  to  a  point  below  the  level  of  the  contained  liquid 
(see  Fig.  96),  the  acid  may  be  added  from  time  to  tune  in  exactly  the 
quantities  necessary  to  produce  the  best  effect,  No  gas  can  escape  by  this 

funnel-tube,  as  its  extremity  within  the  vessel  is  always  cov- 

.  . , 

ered  by  the  fluid. 

The  theory  of  the  liberation  of  hydrogen  in  this  process  is  as 
follows :  neither  zinc  or  iron  are  capable  of  uniting  directly,  as 
metals,  with  sulphuric  acid;  but  oxyd  of  zinc  and  of  iron 
combine  readily  with  it.  Thus  a  decomposition  of  water  is 
determined.  The  zinc  or  iron  takes  oxygen  from  the  water, 
and  forms  oxyds  of  these  metals  respectively,  while  the  hydro- 
gen before  in  combination  with  the  oxygen  passes  off  in  the- 
gaseous  form.  The  oxyds  of  zinc  and  iron  formed  are  inso- 
luble in  water,  but  are  readily  dissolved  by  the  sulphuric  acid, 
forming  salts  of  sulphate  of  iron  or  zinc.  The  surface  of  the  metal  is  thus  left 
clean  and  exposed  to  the  water,  from  which  it  attracts  another  portion  of 
oxygen,  which  is  dissolved  as  before.  The  reaction  which  takes  place  may 
be  expressed  by  the  following  equation  : — 

Zn+SOg-t-HO-Zn  0,  SOs+H. 

Sulphuric  acid  does  not  take  any  direct  part  in  the  decomposition  of  the 
•water ;  but  its  presence  seems  to  facilitate  the  processes  by  increasing  the  af- 
finity between  the  metal  and  the  oxygen  of  the  water ;  it  also  dissolves  the 
oxyd  as  fast  as  it  is  formed,  which  is  essential  to  the  continuance  of  the  ac- 
tion. 

294.  Properties  . — Hydrogen  is  a  colorless  gas,  which  has  never  been 
liquefied.  When  pure,  it  is  without  taste  or  odor,  but  as  prepared  in  the  way 
last  described,  it  has  a  nauseous,  disagreeable  odor,  arising  from  the  presence 
of  impurities  contained  in  the  materials  used.  It  is  slightly  soluble  in  water, 
and  does  not  support  respiration :  an  animal  plunged  in  it  soon  dies  for  want 
of  oxygen.  "When  mingled  •with  a  large  quantity  of  air,  it  may  be  breathed 
for  a  time  without  inconvenience,  and  the  voice  of  the  person  inhaling  it,  ac- 
quires a  peculiar  shrill  squeak.  Sounds  produced  in  this  gas  are  hardly  per- 
ceptible. 

Hydrogen  is  the  lightest  substance  in  nature,  being  sixteen  times  lighter 
than  oxygen,  and  14'4  lighter  than  air ;  100  cubic  inches  of  it  weigh  only 
2 '14  grains.  Owing  to  its  levity,  it  has  been  extensively  used  in  filling  bal- 
loons, which  begin  to  rise  when  the  weight  of  the  material  of  which  they 
are  made  and  the  hydrogen  together,  are  less  than  the  weight  of  an  equal 
bulk  of  ah*.  At  the  present  time,  coal  gas,  owing  to  the  greater  facility  with 
Which  it  can  be  obtained,  is  generally  substituted  in  the  place  of  hydrogen  for 

QUESTIONS. — What  is  the  theory  of  the  liberation  of  hydrogen  under  such  circumstances  ? 
"What  is  the  chemical  reaction  ?  What  part  does  the  sulphuric  acid  sustain  ?  What  are 
the  properties  of  hydrogen  ?  What  is  said  of  the  lightness  of  hydrogen  ? 


HYDROGEN.  203 

• 

aerostatic  purposes — although  of  much  greater  density.  Soap-bubbles  inflated 
with  hydrogen  rise  rapidly  through  the  air.  In  order  to  obtain  these  bubbles, 
we  fill  a  bladder,  or  gas-bag,  provided  with  a  stop-cock,  with  hydrogen  gas, 
and  attach  to  the  stop-cock  a  common  tobacco-pipe,  or  what  is  better,  one  of 
metal.  (See  Fig.  99.)*  The  extremity  of  the  pipe  is  dipped  into  soap-suds, 
and  the  bubbles  are  blown  by  opening  the  stop-cock  and  gently  pressing  tho 
bladder. 

Hydrogen,  beside  being  the  lightest  body  in  nature,  possesses  also  tho 
greatest  tenuity,  and  there  is  reason  for  supposing  that  its  atoms  or  molecules 
are  smaller  than  those  of  any  other  known  substance.  No  receptacle  that  is 
at  all  porous,  as  a  bladder  or  India-rubber  bag,  can  be  used  for  storing  hy- 
drogen for  any  considerable  length  of  time,  the  remarkable  law  of  the  diffu- 
sion of  gases  already  explained  (§  52,  p.  39)  promoting  its  escape,  and  caus- 
ing an  interchange  of  the  surrounding  air.  Faraday,  in  an  attempt  to  liquefy 
hydrogen  through  the  agency  of  cold  and  pressure,  found  that  it  would  leak 
freely  with  a  pressure  of  28  atmospheres  through  stop-cocks  which  were  per- 
fectly tight  with  nitrogen  at  60  atmospheres.  A  minute  crack  in  a  glass  jar, 
quite  too  small  to  leak  with  water,  will  allow  hydrogen  to  escape  readily. 
Hydrogen  also  enters  into  combination  in  a  smaller  proportionate  weight  than, 
any  other  element,  and  has  hence  been  chosen  as  the  unit  of  the  scale  of 
equivalents.  Owing  to  the  lightness  of  hydrogen,  a  jar  may  bo 
filled  with  it  by  displacement,  without  using  the  pneumatic  FIG.  97. 
trough.  Thus,  if  a  bottle  or  jar  be  inverted  over  the  extremity 
of  an  upright  tube  delivering  the  gas  (see  Fig.  97),  the  air  it 
contains  will  be  entirely  displaced  by  the  hydrogen  rising  into 
it.  The  gas  may  be  retained  for  some  minutes,  even  when  re- 
moved from  the  source  of  supply,  provided  the  jar  be  still  held 
in  an  inverted  position ;  but  if  its  mouth  be  turned  upward,  the 
gas  almost  immediately  escapes. 

295.  Combustion   of   Hydrogen . — Hydrogen  is  ex- 
tremely inflammable ;  when  a  lighted  taper  is  plunged  into  a 
jar  of  it,  the  gas  takes  fire,  but  the  taper  is  extinguished,  since 
there  is  no  oxygen  above  the  mouth  of  the  jar  to  support  com- 
bustion.    This  experiment  is  best  shown  by  thrusting  up  a 
lighted  bit  of  candle  into  an  inverted  jar,  or  bottle  of  hydrogen. 
The  ignited  gas  burns  quietly  at  the  mouth  of  tho  jar,  and  the  extinguished 
candle  may  be  again  relighted  by  it.     If  the  bottle  is  suddenly  reversed  after 
the  gas  has  burned  awhile,  the  remaining  gas  will  burst  into  flame  with  a 
slight  explosion. 

•  India-rubb«r  gas-bags,  -with  metal  pipes,  stop-cocks,  etc.,  are  prepared  especially  for 
this  purpose  by  dealers  in  chemical  apparatus.  A  tobacco-pipe  attached  to  the  India- 
rubber  delivery-tube  of  a  gasometer  may  also  be  employed. 

QUESTIONS. — What  of  its  tenuity  and  smallness  of  particles  ?  What  are  some  illustra- 
tions of  these  properties  ?  Why  has  hydrogen  been  chosen  as  the  unit  of  the  scale  of 
equivalents  ?  What  is  said  of  the  inflammability  of  hydrogen  ? 


204  INORGANIC     CHEMISTRY. 

A  jet  of  hydrogen  bums  with  a  bluish  white  flame,  and  a  feeble  light.     The 
experiment  can  be  shown  by  adapting  to  the  cork  of  a  flask  from  which  hy- 
FIQ.  98.        drogen  is  evolved,  a  piece  of  pipe-stem,  or  a  small  glass  tube 
drawn  out  to  a  point.     (See  Fig.  98.) 

If  a  dry,  cold  tumbler  be  held  over  a  jet  of  burning  hydro- 
gen, its  interior  will  rapidly  become  covered  with  a  copious 
deposition  of  moisture.  This  results  from  a  condensation  of 
the  vapor  of  water  produced  by  the  union  of  the  hydrogen 
with  the  oxygen  of  the  atmosphere. 

296.  Explosion  of  Mixed  Oxygen  and  Hy- 
drogen . — If  the  hydrogen  before  being  kindled  is  mixed 
with  air  sufficient  to  burn  it  completely,  or  with  between  two 
and  three  times  its  volume,  and  then  ignited,  combustion  takes 
place  instantaneously  throughout  the  whole  mass,  and  is  attended  with  a  vio- 
lent explosion.  Hence  particular  caution  is  necessary  in  using  hydrogen  to 
avoid  the  slightest  admixture  of  common  air. 

When  pure  oxygen  is  substituted  in  the  place  of  air,  the  explosion  is  much 
more  violent. 

A  mixture  of  oxygen  and  hydrogen  will  never  unite  under  ordinary  cir- 
cumstances of  temperature  and  pressure ;  but  the  passage  of  an  electric  spark, 
or  the  application  of  an  intensely  heated  body,  will  cause  instantaneous  union, 
accompanied  by  an  explosion.  The  product  of  such  combination  is  always 
water. 

In  illustrating  by  experiment  the  explosive  combination  of  oxygen  and  hy- 
drogen, the  proportions  which  produce  the  best  effect  are  2  of  hydrogen  to  5 
of  air,  or  2  of  hydrogen  to  1  of  oxygen.  As  the  explosions  are  most  violent, 
small  quantities  only  of  the  mingled  gases  can  be  safely  employed. 

The  experiments  may  be  varied  by  inflating  a  soap-bubble  with  the  gas- 
eous mixture,  and  igniting  it 

with  a  candle  as  it  ascends ;  FlQt  "• 

or  by  blowing  up  a  quantity 
•of  bubbles  in  a  shallow  dish, 
as  is  represented  in  Fig.  99; 
or  by  filling  a  bladder  with 
the  mixed  gases,  and  ignit- 
ing it  from  a  distance  by 
means  of  a  candle  fixed  to  ^sj 
the  end  of  a  pole. 

What  is  called  the  hydrogen-gun  consists  of  a  strong  tin  tube,  about  an 
inch  in  diameter  and  eight  inches  in  length,  open  at  one  end  and  provided 
with  a  small  vent  hole  at  the  other.  In  loading  it,  the  vent  is  stopped  by 

QUESTIONS.—  What  are  the  peculiarities  of  the  hydrogen  flame  ?  If  a  cold  glass  tum- 
bler be  held  over  the  jet,  what  phenomenon  is  noticed  ?  If  hydrogen,  before  ignition,  be 
mingled  with  air,  what  happens  ?  Will  oxygen  and  hydrogen  unite  of  their  own  accord  ? 
What  are  the  best  explosive  mixtures  of  oxygen  and  hydrogen  *  How  may  the  explosive 
effects  of  mixed  hydrogen  and  oxygen  be  illustrated  ?  Explain  the  hydrogen-gun. 


HYDROGEN.  205 

•wax,  the  tube  filled  with  -water,  and  the  proper  mixture  of  gases  introduced 
from  a  receiver  under  water.  The  tube  thus  filled  is  closed  with  a  cork,  and 
afterward  fired  at  the  vent.  The  explosion  is  sufficient  to  expel  the  cork 
with  violence,  and  produce  a  loud  report.  The  same  experiment  may  be 
more  simply  performed  by  inverting  a  vial,  or  test  tube  over  a  jet  of  hydro- 
gen, and  allowing  the  escaping  gas  to  mingle  with,  but  not  wholly  displace  the 
air.  The  mixture  thus  obtained  may  be  exploded  by  applying  flame  to  the 
mouth  of  the  tube. 

The  loud,  sharp  report  which  attends  the  combination  of  oxygen  and  hy- 
cro^en  under  these  circumstances,  is  explained  as  follows : — The  steam,  which 
i.-s  the  resulting  product  of  the  union,  suddenly  expands  from  the  high  tem- 
perature attendant  on  the  combustion,  and  immediately  afterward  condenses  • 
great  dilatation  is  first  produced,  followed  by  the  formation  of  a  partial  vacuum ; 
the  surrounding  air  rushes  in  to  fill  the  void,  and  by  the  collision  of  its  par- 
ticles produces  the  report.* 

The  inflammation  of  an  explosive  mixture  of  oxygen  and  hydrogen,  or  of 
hydrogen  alone,  in  contact  with  air,  is  not  only  effected  by  a  lighted  taper,  or 
the  electric  spark,  but  it  likewise  takes  place  in  the  cold  by  the  action  of  cer- 
tain substances,  the  principal  of  which  is  "platinum  sponge,"  or  platinum  in 
a  loosely  coherent  state,  f 

If  we  throw  a  piece  of  platinum  sponge  into  a  vessel  containing  a  mixture 
of  2  parts  of  hydrogen  to  1  of  oxygen,  a  combination  of  the  two  gases,  ac- 
companied by  an  explosion  immediately  ensues.  The  same  thing  also  takes 
place,  but  more  slowly,  when  a  thin  plate  of  platinum,  rendered  chemically 
clean,  is  employed. 

This  phenomenon  has  been  considered  as  one  of  catalysis  (p.  161),  or  in 
other  words,  as  due  solely  to  the  mere  presence  of  the  platinum ;  but  it  is 
now  generally  believed  to  be  the  result  of  adhesion  (§  48).  The  gases,  it  is  sup- 
posed, by  reason  of  a  strong  adhesion  to  the  metal,  are  condensed  upon  its 
surface,  and  being  thus  brought  within  the  sphere  of  each  other's  attraction, 


*  "The  whole  range  of  natural  phenomena,"  says  Professor  Faraday,  "  does  not  pre- 
sent a  more  •wonderful  result  than  this  violent  combination  of  oxygen  and  hydrogen. 
Well  known  and  familiar  though  it  be — a  fact  standing  on  the  rery  threshold  of  chem- 
istry— it  is  one  which  I  ponder  over  again  and  again  with  wonder  and  admiration.  To 
think  that  these  two  violent  elements,  holding  in  their  admixed  parts  a  force  of  the  most 
extraordinary  kind — a  force  which,  if  we  reduce  it  to  a  certain  kind  of  comparison,  will  be 
found  equal  to  the  power  of  many  thunder-storms— should  wait  indefinitely  until  some 
cause  of  union  be  applied,  and  then  furiously  rush  into  combination,  and  form  the  bland, 
unirritating  liquid,  water; — is  to  me,  I  confess,  a  phenomenon  which  continually  awakens 
new  feelings  of  wonder  as  often  as  I  view  ft" 

t  Platinum  sponge  is  easily  prepared  by  soaking  a  small  piece  of  bibulous  paper  in  a 
solution  of  platinum  (the  bi-chloride  of  platinum)  and  afterward  drying  and  igniting  it. 
A  little  pellet  of  asbestos  maybe  substituted  with  advantage  in  place  of  the  paper.  The 
sponge,  after  a  little  time,  loses  its  peculiar  property,  bnt  it  can  be  again  restored  by  being 
Btrongly  ignited. 

QUESTIONS. — What  occasions  the  detonation?  How  may  a  mixture  of  oxygen  and  hy- 
drogen be  exploded  without  the  direct  application  of  an  ignited  substance?  What  is 
spongy  platinum  ?  What  experiment  illustrates  its  action  ? 


206 


INORGANIC     CHEMISTRY. 


unite.  By  the  act  of  combination  heat  is  evolved — the  platinum  becomes 
red  hot — the  remaining  uncombined  gases  are  ignited  by  it,  and  an  explosion 
occurs. 

Other  finely  divided  substances  beside  platinum  possess  this  property  of 
favoring  tha  combination  of  oxygen  and  hydrogen  in  an  inferior  degree. 
Even  pounded  glass,  charcoal,  pumice,  rock-crystal,  etc.,  if  warmed  to  600° 
F.  produce  this  effect.  Finely  divided  palladium,  rhodium,  and  iridiura  act 
in  the  same  manner  as  platinum. 

If  we  project  a  jet  of  hydrogen  alone  upon  platinum  sponge,  this  substance 
becomes  incandescent,  and  the  gas  inflames. 

297.    Dobereiner's     Inflammable     Lamp.  —  Advantage  has 


FIG.  100. 


been  taken  of  this  circumstance  to  construct  a  machine  for 
obtaining  fire  instantly  by  means  of  hydrogen  gaa  It 
consists  of  a  conical  glass,  Fig.  100,  attached  to  a  plate  and 
stop-cock,  and  suspended  in  a  receiver,  a,  containing  sul- 
phuric acid  and  water.  Within  the  outer  vessel  a  piece  of 
zinc,  z,  is  suspended,  and  this  by  contact  with  the  dilute 
acid  evolves  hydrogen.  The  gas  accumulating  in  the  in- 
ner vessel  forces  the  acid  into  the  outer  vessel,  until  it  no 
longer  touches  the  zinc,  and  thus  stops  the  further  evolu- 
tion of  hydrogen.  By  opening  the  stop-cock,  c,  the  accu- 
\  mulated  gas  issues  upon  a  ball  of  spongy  platinum,  d,  and 
almost  immediately  takes  fire.  As  fast  as  the  gas  escapes 
from  the  interior  vessel,  the  sulphuric  acid  which  has  been 
displaced  rises  to  take  its  place,  and  again  coming  in  contact  with  the  zinc, 


FIG.  101. 


evolves  a  fresh  supply  of  hydrogen. 

298.  Musical  Tones . — if  a  glass  tube,  open  at 
both  ends,  be  held  over  a  jet  of  burning  hydrogen  (see  Fig. 
101),  a  rapid  current  of  air  is  produced  through  the  tube, 
which  occasions  a  flickering  of  the  flame,  attended  by  a 
series  of  small  explosions,  that  succeed  each  other  so  rap- 
idly, and  at  such  regular  intervals,  as  to  give  rise  to  a 
musical  note,  or  continuous  sound,  the  pitch  and  quality 
of  which  varies  with  the  length,  thickness,  and  diameter 
of  the  tube.  By  sounding  the  same  note  with  the  voice,  a 
tuning-fork,  or  musical  instrument,  the  singing  of  the 
flame  may  be  interrupted,  or  caused  to  cease  entirely ;  or 
when  silent,  to  recommence. 

299.  Heat  Generated  by  the  Combustion 
of  Hydrogen . — The  flame  of  hydrogen,  although 
slightly  luminous,  produces  a  great  degree  of  heat.  When 
the  combustion  is  assisted  by  oxygen  gas,  the  heat  gen- 

Q0K8TION8.—  What  other  substances  possess  similar  properties  ?  When  a  jet  of  hydro- 
gen is  thrown  upon  spongy  platinum,  what  ensues  ?  What  is  the  construction  of  Dobe- 
reiner's lamp  ?  When  hydrogen  is  burned  from  a  jet  in  a  tube,  what  phenomenon  it  no- 
ttced  ?  What  is  said  of  the  heating  effects  of  the  hydrogen  flame  ? 


H  Y  D  11  O  G  E  N  . 


207 


FIG.  102. 


erated  is  most  intense,  and  is  only  exceeded  by  that  produced  by  electrical 

agency. 
300.  Oxy  hydrogen   Blow -pipe. 

— The  practical  arrangement  for  effecting 

the  combustion  of  hydrogen  by  oxygen, 

is    known    as    the    "  Oxy hydrogen"   or 

"  Compound"  Blow-pipe.     As  commonly 

constructed,  it  consists  of  two  gasometers, 

containing,  the  one  oxygen,  and  the  other 

hydrogen.    (See  Fig.  102.)    Tubes  leading 

from  these  are  brought  together  at  their 

extremities,  and  the  two  gases  delivered 

from  apertures  situated  l-30th  of  an  inch 

apart,  are  burned  in  a  single  jet.     The 

best  result  is  attained  by  so  arranging  the 

Stop-cocks  of  tho  gasometers,    that    the 

volume  of  hydrogen  flowing  out  shall  be 

double  that  of  the  oxygen. 

The  effects  of  the  compound  blow-pipe 

may  be  produced  in  a  degree  by  passing 

a  stream  of  hydrogen  through  the  flame 

of  a  spirit-lamp,  as  is  represented  in  Fig. 

103. 

The  effects  of  the  oxyhydrogen  blow- 
pipe are  very  remarkable.     Substances  that  are  infusible  in  tho  most  intense 
pIG   jog  blast  furnaces,  melt  in  the  heat  of 

its  focus  with  the  rapidity  of  wax. 
Iron,  copper,  zinc,  and  other  metals, 
melt  and  burn  in  it  readily ;  tho 
first  (when  a  watch-spring  or  steel 
file  is  employed)  with  beautiful  scin- 
tillations, and  tho  latter  with  char- 
acteristic colored  flames.  Thick 
platinum  "wire  melts  in  it  with  ease, 

and  may  be  even  volatilized.     Rock-crystal  can  bo  liquefied  and  drawn  out 

into  threads  like  glass,  and  the  stem  of  a  tobacco-pipo  may  bo  fused  into  an 

enamel-like  bead. 

When  the  jet  of  the  two  gases,   after  being  set  on  fire,  is  directed  under 

water,  it  continues  to  burn  beneath  the  surface  of  the  liquid,  in  tho  form  of  a 

globe,  and  fuses  and  burns  metallic  wires  hell  in  it. 

301.  D  r  u  m  m  o  n  d    Light  —Tho  flame  of  tho  oxyhydrogen  blow-pipo 

is  very  pale  in  itself,  but  diffuses  a  dazzling  light  as  soon  as  any  solid  body 

is  introduced  into  it.     By  causing  the  flame  to  fall  upon  a  cylinder  of  quick- 


. — Describe  the  oxyhydrogen  blow-pipe.     What  are  some  of  the  effects  pro- 
duced by  it  ?    What  is  the  Drummond  light  ? 


208  INORGANIC     CHEMISTRY. 

lime,  an  artificial  light  is  produced,  which  for  whiteness  and  brilliancy  may  bo 
compared  to  the  sun  itself.  With  the  requisite  supply  of  gases  this  light  may 
be  maintained  for  hours,  care  being  taken  to  exposo  to  the  flame  fresh  sur- 
faces of  the  lime,  by  causing  it  to  revolve  by  clock-work  continually,  but 
slowly.  This  light  is  generally  known  as  the  "  Drummond  Light,"  from  tho 
name  of  an  English  engineer,  who  first  Used  it  for  signalizing  at  great  dis- 
tances ;  it  is  also  often  termed  the  "  lime  light." 

The  distances  at  which  this  light  may  be  seen  when  its  rays  are  concen- 
trated by  a  parabolic  mirror,  are  Very  great.  In  one  instance,  during  tho 
prosecution  of  the  trigonometrical  survey  of  Great  Britain,  it  wag  seen  by 
observers  stationed  upon  a  mountain  peak,  at  a  distance  of  108  miles,  during 
daylight. 

The  combination  of  hydrogen  with  other  bodies  is  not  attended  with  tho 
development  of  light  and  heat,  with  the  exception  of  oxygen  and  chlorine- 
two  of  the  most  highly  electro-negative  of  all  known  substances. 

302.  The  Chemical  Characteristics  of  Hydrogen  ally 
it  very  .closely  with  the  metals — particularly  with  zinc  and  copper — and  thero 
are  some  reasons  for  supposing  that  it  is  itself  a  metal,  exceedingly  volatile, 
and  sustaining  in  this  respect  the  same  relation  to  mercury,  that  mercury 
does  to  platinum.  The  fact  that  it  is  wanting  in  luster,  hardness,  and  bril- 
liancy— qualities  which  are  popularly  considered  as  essential  attributes  of  tho 
metals — is  no  argument  against  this  supposition,  inasmuch  as  mercury,  when 
vaporized  through  heat,  is  as  transparent  and  colorless  as  hydrogen  itself. 
The  vapor  of  mercury  and  of  other  volatile  metals  is  also,  like  hydrogen,  a 
non-conductor  of  heat  and  electricity.  Yet  mercury,  in  tho  state  of  vapor,  is 
no  less  a  metal  than  in  its  ordinary  condition. 

Although  hydrogen  is  the  lightest  and  the  most  attenuated  substance  in 
nature,  and  combines  in  the  emallest  proportional  quantity  of  all  the  elements, 
its  active  power,  considered  in  relation  to  its  combining  weight,  is  very  great. 
Thus,  it  combines  with  chlorine  in  the  ratio  of  1  part  by  weight  to  36  ;  with 
bromine  1  to  80  5  and  with  iodine  as  1  to  125  j  yet  in  each  case  it  abun- 
dantly satisfies  the  combining  affinities  of  the  other  elements,  generates  by 
its  union  powerful  and  not  easily  decomposed  acids,  and  in  every  other  re- 
spect manifests  an  equality  of  force.  This  circumstance  of  so  much  power 
existing  hi  connection  with  so  little  ponderable  matter,  is,  regarded  by  Pro- 
fessor Faraday,  as  one  of  the  most  remarkable  characteristics  of  hydrogen. 

303.  Compounds  of  Hydrogen  with  Oxygen, — But  two 
compounds  of  hydrogen  with  oxygen  are  certainly  known  to 
exist* — the  protoxyd  of  hydrogen,  or  water,  whose  chem- 

*  According  to  some  authorities,  there  is  a  third  compound— the  saboxyd  of  hydrogen 
—formed  by  the  gradual  absorption  of  hydrogen  by  water. 

QUESTIONS. — To  what  distance  is  this  light  visible  ?  Are  the  combinations  of  hydrogen 
generally  accompanied  by  evolutions  of  light  and  heat?  What  is  said  of  the  nature  of 
hydrogen  ?  What,  according  to  Faraday,  is  one  the  most  remarkable  characteristics  of 
hydrogen  ?  What  compounds  does  hydrogen  form  with  oxygen  1 


HYDROGEN.  209 

ical  symbol  is  HO,  and  the  peroxyd  or  binoxyd,  whose 
symbol  is  H0.2.  Water  is  the  only  natural  combination  ; 
the  binoxyd  being  an  artificial  preparation. 

304.  VV  a  t  e  r  is  the  most  important,  and  at  the  same  time  the  most  re- 
/markable  of  all  chemical  compounds.     It  is  the  most  abundant  substance  ex- 
isting in  a  separate  condition  upon  the  face  of  the  earth,  and  covers  to  an 
unknown  depth  three  fourths  of  its  surface.     Water  enters  largely  into  the 
composition  of  nearly  all  organized  matter,  and  of  every  structure  that  pos- 
sesses corporeal  vitality,  it  is  an  essential  element.* 

305.  Composition    of   Water . — Water,  as  has  been  already  stated, 
is  formed  by  the  union  of  two  volumes  of  hydrogen  and  one  of  oxygen,  or 
by  weight,  of  8  parts  of  oxygen  to  1  of  hydrogen.     The  composition  of  water 
by  measure  and  by  weight,  upon  which,  as  a  basis,  the  whole  theory  of  atomic 
constitution  and  the  doctrine  of  equivalent  proportions  rests,  may  be  proved 
by  a  great  variety  of  experiments,  both  by  analysis  and  by  synthesis. 

By  analysis,  by  decomposing  water  by  the  galvanic  current  (§  242,  p.  148), 
and  by  passing  the  vapor  of  water  over  red  hot  iron  (§  293).  By  synthe- 
sis, by  uniting  the  two  gases  in  proper  proportions  by  combustion — by  the 
action  of  spongy  platinum — by  the  electric  spark — and  by  passing  a  current 
of  hydrogen  over  oxyd  of  copper,  heated  to  bright  redness. 

The  most  reliable  synthetical  process  is  that  last  indicated.  The  hydrogen 
passing  over  the  heated  metallic  oxyd,  combines  with  its  oxygen  and  forms 
water,  which  passes  off  as  steam — the  copper  being  left  in  a  metallic  state, 
the  steam  collected  and  condensed  gives  the  weight  of  the  water  formed ;  the 
loss  in  weight  which  the  metallic  oxyd  experiences  gives  the  weight  of  the 
oxygen  which  has  entered  into  the  composition  of  the  water ;  and  the  dif- 
ference between  these  two,  gives  the  weight  of  the  hy-  FIG.  104. 
drogen  contained  in  the  water. 

Eudiometer . — An  apparatus  by  which  a  mixture 
of  oxygen  and  hydrogen  can  be  exploded  by  the  electric 
spark,  and  the  resulting  product  collected  and  examined, 
is  termed  an  Eudiometer.  It  consists  of  a  graduated 
glass  tube  usually  placed  over  mercury,  and  so  arranged 
that  an  electric  spark  can  be  passed  into  its  interior.  (See 
Fig.  104.)  When  a  mixture  of  oxygen  and  hydrogen  is  ex- 
ploded in  such  a  tube  over  mercury,  a  vacuum  is  formed 

*  A  man  of  154  Ibs.  -weight  is  made  up  of  116  Ibs.  of  water  and  only  38  Ibs.  of  dry 
matter:  yet  tbis  proportion  of -water  is  small  in  comparison  -with  the  amount  that  enters 
i-ito  the  economy  of  certain  of  the  lower  orders  of  animals.  Of  that  class  of  sea-animals 
known  as  the  medusas,  for  example,  it  is  estimated  that  at  least  99-100ths  of  their  whole 
structure  by  weight  consists  of  water.  They  have,  therefore,  not  inaptly  been  termed 
"  living  forms  of  water." 

QUESTIONS.—  What  is  said  of  water  ?  What  is  the  composition  of  water  by  measure  and 
weight  ?  How  is  the  composition  of  water  proved  by  analysis  ?  How  by  synthesis  ? 
What  is  the  most  reliable  synthetical  method,  and  how  is  the  composition  of  water  calcu- 
lated from  the  results  obtained  ?  What  is  an  eudiometer  ? 


210  INORGANIC     CHEMISTRY. 

by  reason  of  their  union  and  condensation,  and  the  mercury  rises  to  fill  it. 
If  the  gases  are  mingled  in  the  exact  proportion  to  form  water,  the  com- 
bination will  be  complete,  and  both  will  disappear  entirely.  If,  however, 
one  of  the  two  elements  is  in  excess,  a  gaseous  residuum  will  remain.  Thus, 
suppose  we  introduce  into  the  eudiometer  100  measures  of  hydrogen  and 
75  of  oxygen,  we  shall  find  after  combustion  25  of  oxygen  remaining,  but 
none  of  hydrogen.  Therefore,  100  of  hydrogen  have  combined  with  50  of 
oxygen,  or  the  union  has  taken  place  in  the  proportion  of  2  volumes  to  1. 
The  graduations  marked  on  the  eudiometer  tube  enable  us  to  proportion 
the  quantities  of  the  gases  to  be  introduced,  and  also  to  estimate  by  tho 
space  unoccupied  the  volume  of  the  residuum  remaining  after  the  combination. 

306.  History . — The  history  of  water  constitutes  one  of  the  most  inter- 
esting portions  of  the  whole  record  of  physical  philosophy.  The  old  Greek 
philosopher  Thales,  in  the  earliest  dawn  of  scientific  speculation,  taught  that 
water  was  the  "  first  and  fontal"  element  of  all  material  things — the  earliest 
created  substance.  At  a  subsequent  period,  it  was  considered  to  be  one  of 
four  primal  elements;  earth,  air,  and  fire  being  the  other  three.  This  vie\v 
of  the  elementary  character  of  water  remained  unquestioned  until  nearly  tho 
close  of  the  18th  century,  or  about  the  time  of  the  first  French  revolution. 
Von  Helmont,  a  contemporary  of  Galileo,  and  one  of  the  most  eminent  scien- 
tific men  of  his  day,  maintained  the  doctrine  that  water  was  convertible  into 
earth,  and  the  following  experimental  results  were  appealed  to  as  affording 
indisputable  evidence  of  the  fact,  viz.,  that  a  tree  when  transferred  from  earth 
to  water  continues  to  develop  itself  and  derive  solid  constituents  from  the 
liquid;  and  that  when  water  was  evaporated  to  dryness  in  a  vessel,  an 
earthy  residuum  always  remained.  The  inference  from  these  experiments  wa-s 
not,  however,  that  water  was  a  compound  body,  but  rather  that  it  possessed 
a  generative  character,  and  produced  all  tho  elements  necessary  for  vegetable 
existence.* 

Sir  Isaac  Newton,  in  1704.  in  the  course  of  his  optical  researches,  remarked 
that  water  and  the  diamond  both  refracted  light  in  the  same  way  as  sub- 
stances of  a  highly  inflammable  character,  lie  in  consequence  predicted  the 


*  It  is  not  a  little  singular  that  the  compound  character  of  water  should  have  remained 
so  long  undetected  by  the  Egyptians,  Greeks,  and  Romans,  who  carried  some  branches 
of  economical  chemistry  to  a  high  degree  of  perfection,  or  in  later  times,  by  the  Arabian 
chemists,  or  the  mediaeval  alchemists.  It  would  seem  as  if  the  phenomena  of  vegetation, 
and  of  animal  life,  if  they  had  been  watched  with  attention,  would  have  shown  that  thu 
elementary  character  of  water  was  a  most  questionable  doctrine.  "  Not  a  weed  ever  grew 
but  what  was  possessed  of  the  secret  of  its  composite  nature  ;  not  an  animalcule  overlived 
but  daily  decomposed  and  changed  the  '  indivisible'  into  its  own  structure.  No  one,  how- 
ever, understood  their  language,  or  tried  to  interpret  it,  and  hieroglyphics  which  seem  to 
us  pictures  which  tell  their  own  story,  revealed  nothing  to  those  who  had  already  decided 
that  they  had  no  meaning." 

QUESTIONS— How  may  the  composition  of  water  be  determined  by  the  use  of  the  en- 
diometer?"  What  opinions  were  formerly  entertained  respecting  the  nature  of  water? 
What  doctrine  respecting  water  was  advanced  by  Von  Helmont  ?  Upon  what  did  he  base 
hia  conclusions?  What  facts  were  ascertained  by  Sir  Isaac  Newton? 


HYDROGEN.  211 

future  combustion  of  the  diamond,  and  it  is  inferred  that  he  anticipated,  in 
a  like  manner,  the  combustibility  of  one  of  the  elements  of  water. 

Three  quarters  of  a  century  after  this,  Lavoisier  devised  and  carried  out 
an  experiment  which  is  regarded  as  the  commencement  of  the  modern  sys- 
tem of  chemistry.  He  doubted  the  conclusions  of  Yon  Helmont,  "  and  he 
asked  nature  if  water  could  or  could  not  be  turned  into  stone,  and  asked  in 
such  a  way  that  she  granted  an  intelligible  and  unmistakable  answer.  Ho 
took  an  alembic,  which  may  be  described  as  an  air-tight  still  or  retort,  in  which 
the  condensed  steam  or  distilled  liquor  always  flows  back  into  the  boiler — 
weighed  it — put  an  ascertained  quantity  of  water  in  it — made  it  air-tight — 
and  set  the  water  boiling ;  the  steam  or  distilled  liquor  rising,  became  con- 
densed, and  continually  trickled  back  through  the  tubular  arms  of  the  alem- 
bic into  the  original  vessel.  This  arrangement  was  kept  boiling  for  one 
hundred  and  one  days  and  nights.  At  the  end  of  that  period,  the  whole  ap- 
paratus had  lost  no  weight;  the  alembic,  however,  had  lost  17  grains,  but 
the  water  had  gained  weight,  and  was  muddy  with  earthy  particles.  "When 
this  muddied  water  was  evaporated  to  dryness,  there  remained  20  grains  of 
earth,  17  of  which  had  clearly  been  worn  out  of  the  substance  of  the  vessel ; 
but  where  had  the  other  3  come  from  ?  Lavoisier  at  first  assigned  them  to 
the  incidental  errors  of  the  experiment,  but  it  was  afterward  shown  that  they 
were  derived  from  the  water  itself — from  the  saline  and  organic  matter 
which  it  held  in  solution.  Thus  the  earth,  which  Von  Helmont  traced  to 
the  transformation  of  water,  was  discovered  to  have*come  from  the  earthy 
vessel  in  which  the  water  had  been  continuously  boiled.  Scheele,  an  eminent 
Swedish  chemist,  followed  up  the  experiment,  by  analyzing  the  earth  pro- 
duced, and  proved  it  to  be  the  same  as  the  material  of  the  apparatus. 

"  The  notable  circumstance  in  this  experiment  is  the  use  of  the  balance. 
Until  this  weighing  of  the  alembic  the  balance  had  not  been  used  in  chem- 
istry as  an  implement  of  research.  Quality  and  not  quantity  was  only  re- 
garded. But  when  Lavoisier  ordered  a  balance  with  a  view  to  its  employ- 
ment in  research,  the  fate  of  old  theories  was  sealed.  The  very  thought  of 
the  balance  implied  the  perception,  by  him  that  thought  of  it,  of  the  central 
idea  of  all  positive  chemistry,  namely,  .that  every  chemical  operation  ends  in 
an  equation;  and  that  if  100  grains,  ounces,  or  pounds  of  any  substance 
whatsoever  are  burned,  distilled,  or  in  any  way  altered  by  a  chemical  process, 
then  100  pounds,  ounces,  or  grains  of  material  must  be  accounted  for  after  the 
operation,  for  nothing  is  ever  lost." — BREWSTER. 

A  few  years  after  this  experiment  of  Lavoisier,  oxygen  was  discovered, 
and  hydrogen  first  correctly  described  by  Cavendish.  Subsequently  the  com- 
position of  water  was  discovered  almost  simultaneously  by  James  Watt,  the 
inventor  of  the  steam-engine,  by  Cavendish,  and  by  Lavoisier ;  the  first  two 
by  burning  hydrogen  in  oxygen,  and  the  last  by  decomposing  the  vapor  of 
water. 


QUESTIONS. — What  experiment  was  instituted  by  Lavoisier  ?    What  were  the  results  of 
this  experiment  ?   What  was  the  most  noticeable  circumstance  attending  this  experiment? 


212  INORGANIC    CHEMISTRY. 

307.  Properties,  —  The  physical  properties  of  water  are  so  well 
known,  and  have  been  discussed  to  such  an  extent  in  the  preceding  depart- 
ments of  this  work,  that  no  lengthened  description  is  necessary  in  the  present 
connection. 

In  its  ordinary  condition  as  a  liquid,  and  free  from  admixture,  water  is  col- 
orless, transparent,  inodorous,  and  tasteless;  it  boils  at  212°  F.,  freezes  at 
32°  F.,  and  evaporates  at  all  temperatures.  It  is  815  times  heavier  than 
an  equal  bulk  of  air. 

:308.  Coloration  of  Water , — The  peculiar  colors  which  large  bodies 
Df  water  assume  have  not  been  satisfactorily  accounted  for.  The  color  of  the 
Dcean  "  on  soundings"  is  generally  of  a  greenish  hue  ;  but  off  soundings  it  ap- 
pears blue.  It  is  maintained  by  some  authorities  that  the  blue  tint  of  tho 
ocean  is  only  apparent,  and  is  owing  to  a  reflection  of  the  most  refrangible 
of  the  rays  of  solar  light  (the  blue)  in  greater  proportion  than  those  which  aro 
less  so.  Sir  Humphrey  Davy  attributed  the  blue  color  of  the  ocean  to  an 
admixture  of  iodine,  and  others  have  referred  the  very  remarkable  bright  blue 
color  of  the  Mediterranean  to  the  presence  of  salts  of  copper ;  but  although 
iodine  exists  in  combination  in  all  sea-water,  and  copper  has  been  found  in 
the  waters  of  the  Mediterranean,  the  quantities  present  do  not  appear  to  be 
sufficient  to  produce  any  perceptible  coloration.  The  coloring  matter  of  the 
Eed  Sea,  which  at  particular  seasons  of  the  year  is  sufficiently  intense  to 
justify  the  appellation  bestowed  upon  this  body  of  water,  has  been  proved  to 
be  owing  to  the  presence  of  a  prodigious  quantity  of  microscopic  plants. 

309.  Transparency  of  the  Sea , — The  transparency  of  the  sea 
varies  with  the  temperature.  The  maximum  of  visibility  under  water,  under 
the  most  favorable  circumstances  does  not  exceed  25  fathoms,  or  150  feet. 

310.  Purity  of  Water, — In  nature,  water  is  never  found 
perfectly  pure. 

Rain- water  collected  hi  the  country  after  a  long  continuance  of  wet  weather 
is  the  purest  natural  water,  but  even  this  always  contains  atmospheric  air, 
and  the  gases  floating  about  in  it,  to  the  extent  of  about  2£  cubic  inches  of 
air  in  100  of  water.  After  rain-water,  in  the  order  of  purity,  comes  river- 
water  ;  next  the  water  of  lakes  and  ponds ;  next  ordinary  spring  waters ;  and 
then  the  waters  of  mineral  springs.  Succeeding  these  are  the  waters  of  great 
arms  of  the  ocean  into  which  large  rivers  discharge  their  volumes,  as  the 
Black  Sea,  the  water  of  which  is  only  brackish ;  then  the  waters  of  the  main 
ocean ;  then  those  of  the  Mediterranean  and  other  inland  seas ;  and  last  of 
all,  the  waters  of  those  lakes  which  have  no  outlets,  as  the  Dead  Sea,  Cas- 
pian, Great  Salt  Lake  of  Utah,  etc. 

311.  Spring    Waters ,— Spring  water,  although  it  may  be  perfectly 

QUESTIONS.— What  are  the  physical  properties  of  -water?  How  much  heavier  than  air 
is  water  ?  To  what  has  the  coloration  of  bodies  of  water  been  ascribed  ?  What  is  said 
of  the  transparency  of  the  ocean  ?  Is  water  found  pure  in  nature  ?  What  is  the  purest 
natural  water  ?  What  is  the  relative  purity  of  different  waters  ?  What  is  said  of  spring- 
waters? 


HYDROGEN.  213 

transparent,  always  contains  more  or  less  of  mineral  matter  dissolved  in  it. 
The  nature  of  these  substances  will  of  course  vary  with  the  character  of  the 
soil  through  which  the  water  percolates.  The  most  usual  impurities  are  car- 
bonate of  lime,  common  salt,  sulphate  of  lime  (gypsum),  sulphate  and  carbon- 
ate of  magnesia,  and  compounds  of  iron.  Most  spring  waters  also  contain  a 
proportion  of  carbonic  acid  gas. 

312.  Mineral    Springs . — When  the  waters  of  springs  retain  in  so- 
lution so  large  a  proportion  of  mineral  matter  as  to  give  them  a  decided  taste, 
they  are  termed  mineral  waters,  and  are  usually  reputed  to  have  some  medi- 
cinal quality,  varying  with  the  nature  of  the  substance  in  solution. 

Waters  which  contain  iron  in  quantity  sufficient  to  impart  to  them  an  inky 
taste  are  termed  cha-lyb'e-ate;  the  iron  exists  in  the  water  most  frequently 
in  the  state  of  carbonate,  dissolved  in  carbonic  acid,  and  rarely  in  a  propor- 
tion exceeding  one  grain  in  a  pound  of  water. 

Waters*1  impregnated  with  sulphuretted  hydrogen  gas  are  termed  sulphurous, 
or  sulphuretted;  they  may  be  readily  recognized  by  their  nauseous  taste  and 
odor.  Remarkable  springs  of  this  character  exist  at  Sharon,  New  York,  and 
also  in  Virginia. 

313.  Saline    Springs . — Springs  whose  waters  contain  a  large  pro- 
portion of  earthy  or  alkaline  salts,  are  called  saline,  although  this  term  is  gen- 
erally applied  to  particularly  designate  springs  containing  common  salt. 

In  some  springs  carbonic  acid  is  very  abundant,  and  imparts  to  the  water 
an  effervescent,  sparkling  character,  like  that  noticed  in  the  "  Seltzer"  and 
"  Saratoga"  waters. 

314.  T  h  e  r  m  a  1    Springs . — Many  mineral  springs  are  of  a  temperature 
considerably  higher  than  that  of  the  surface  of  the  earth  where  they  make 
their  appearance,  and  not  unfrequently  discharge  boiling  water.     The  major- 
ity of  hot  springs  occur  either  in  the  vicinity  of  volcanoes,  or  they  rise  from 
great  depths  in  rocks  of  the  oldest  geological  periods.     With  few  exceptions, 
they  discharge  at  all  times  the  same  quantity  of  water,  and  their  temperature 
and  chemical  constituents  remain  constant.     There  is  evidence  to  show  that 
the  temperature  of  some  hot  springs  has  not  diminished  for  upward  of  a  thou- 
sand years. 

315.  River-water  is  less  fitted  for  drinking  purposes  than  spring- 
water,  although  it  often  contains  a  smaller  amount  of  dissolved  salts.     But 
river-water  usually  holds  in  solution  or  suspension  large  quantities  of  or- 
ganic matter  of  vegetable  origin,  derived  from  the  surface  of  the  country 
drained  by  the  stream.     If  the  sewerage  of  large  towns  situated  on  its  banks 
be  allowed  to  pass  into  the  stream,  it  is  of  course  less  fit  for  domestic  pur- 
poses. 

Water,  however,  which  is  contaminated  with  animal  and  vegetable  matter, 

QUESTIONS. — When  are  waters  termed  mineral  ?  What  are  chalybeate  waters  ?  What 
are  sulphurous,  or  sulphuretted  waters?  How  may  they  be  recognized?  What  are 
saline  springs ?  What  gives  to  Saratoga  and  Seltzer  waters  their  sparkle?  What  are 
thermal  springs?  In  what,  localities  are  they  generally  found?  What  is  said  of  river- 
water  ?  Can  water  purify  itself? 


214  INORGANIC    CHEMISTRY. 

is  endowed  with  a  self-purifying  power  of  the  utmost  importance.  The  action 
of  the  oxygen  of  the  air  generates  a  species  of  fermentation,  whereby  the  or- 
ganic matters  contained  in  the  water  become  oxydated,  deprived  of  both  color 
and  odor,  and  precipitated  in  part  as  sediment.  The  water  of  the  river  Thames, 
contaminated  with  the  sewerage  of  London,  is  a  remarkable  illustration  of 
this  fact.  Taken  on  board  ships,  it  is  at  first  nauseous,  but  after  standing  in 
casks  for  a  few  days,  it  becomes  sweet  and  wholesome. 

316.  Sea-water* . — The  most  abundant  substance  in  sea- water  is  com- 
mon salt ;  next  the  chloride  of  magnesium  and  the  sulphate  of  magnesia, 
which  compounds  give  to  the  water  its  saline,  bitter  taste ;  then  salts  of  cal- 
cium, potassium,  with  traces  of  iron,  iodine,  bromine,  fluorine,  silver,  and  some 
other  of  the  metals.     The  specific  gravity  of  sea-water  varies  slightly  in  dif- 
ferent locations.     The  waters  of  the  Baltic  and  of  the  Black  Sea  are  less 
salt  than  the  average,  while  those  of  the  Mediterranean  and  some  portions 
of  the  Gulf  of  Mexico,  are  more  so.     The  whole  amount  of  mineral  constitu- 
ents in  the  waters  of  the  main  ocean  ranges  from  3£  to  4  per  cent. 

The  soluble  earthy  matters  washed  from  the  land  by  rains  into  the  rivers, 
and  by  them  carried  into  the  ocean,  remain  there,  since  pure  water  alone 
evaporates  from  the  surface  of  the  ocean.  The  quantity  of  saline  matter, 
therefore,  in  the  ocean  is  continually  accumulating.  It  is  an  error  to  attrib- 
ute the  saltness  of  the  sea  to  the  presence  of  vast  beds  of  mineral  salt ;  but 
fche  sea  undoubtedly  owes  all  its  salts  to  washings  from  the  land.  The 
streams  that  have  flowed  into  it  for  ages  have  been  constantly  adding  to 
the  quantity,  until  it  has  acquired  its  present  briny  and  bitter  condition. 
The  evidence  on  this  point  is  most  conclusive  ;  the  saline  condition  of  sea- 
water  is  but  an  exaggeration  of  that  of  all  ordinary  lakes,  rivers,  and  springs. 
These  all  contain  more  or  less  of  the  mineral  constituents  of  sea- water,  but 
as  their  waters  are  continually  changing  and  flowing  into  the  sea,  the  salts 
in  them  do  not  accumulate. 

Again,  every  lake  into  which  rivers  flow,  and  from  which  there  is  no  out- 
let except  by  evaporation,  is  a  salt  lake ;  and  it  is  extremely  curious  to  ob- 
serve that  this  condition  disappears  when  an  artificial  outlet  is  provided. 
Examples  of  such  lakes  are  the  Dead  Sea,  the  Caspian,  the  Sea  of  Aral, 
and  the  Great  Salt  Lake  of  Utah,  the  saltness  of  all  of  which  greatly  ex- 
ceeds that  of  the  ocean.  Thus  the  waters  of  the  ocean  contain  from  2  to 
3,000  grains  of  saline  matter  in  the  gallon  (70,000  grains) ;  those  of  the  Dead 
Sea,  in  some  places,  11,000  grains,  and  those  of  the  Salt  Lake  of  Utah 
22,000  grains,  or  nearly  one  third  of  their  whole  weight.  In  some  instances, 
even  this  last  proportion  is  exceeded. 

317.  Relative    Fitness   of   Waters  for    Use . — Any  water 
which  contains  less  than  15  grains  of  ordinary  mineral  matter  in  a  gallon  is 
considered  as  comparatively  pure,  and  may  be  employed  for  all  domestic 

QUESTIONS. — "What  is  an  illustration  of  this  fact  ?  What  are  the  mineral  constituents 
of  sea-water  ?  Why  is  the  sea  salt  ?  What  proof  is  there  respecting  the  origin  of  salt 
in  the  ocean  ?  What  is  said  of  the  relative  fitness  of  waters  for  use  ? 


HYDROGEN.  215 

purposes,  provided  it  does  not  contain  too  large  a  proportion  of  organic 
matter.  Water,  of  which  a  gallon  contains  60  grains  of  ordinary  mineral 
matters,  may  be  still  good  for  drinking,  but  it  is  not  fit  for  cooking  vege- 
tables or  washing  linen  when  it  contains  8  grains  to  the  gallon  of  either 
lime  or  magnesia.  Waters  which  contain  6  grains  of  organic  matter  to  the 
gallon  are  not  fit  for  any  domestic  use ;  if  this  limit  is  exceeded,  they  act 
disastrously  upon  the  animal  economy,  and  may  occasion  dysentery  and  va- 
rious other  maladies.  The  presence  of  magnesia  in  considerable  quantity  in 
drinkable  waters  is  undoubtedly  injurious ;  the  use  of  such  waters  in  Swit- 
zarland  is  supposed  to  give  rise  to  the  frightful  diseases  known  as  "  goitre" 
and  "  cretinism."*  The  disagreeable,  earthy  taste  of  certain  well-waters,  in 
most  cases,  arises  from  the  presence  of  alumina,  held  in  solution  by  carbonic 
acid. 

One  of  the  purest  natural  waters  ever  examined  is  that  of  the  river  Loka, 
in  the  north  of  Sweden,  which  flows  mainly  over  granitic  rocks,  upon  which 
water  produces  little  impression.  It  contains  only  l-20th  of  a  grain  (0'05G6) 
of  solid  mineral  matter  per  gallon.  Such  instances,  however,  are  very  rare ; 
but  water  containing  as  little  as  4  or  5  grains  of  solid  matter  to  the  gallon  are 
not  unfrequent.  The  quantity  of  organic  matter  in  water  is  always  greatest 
in  summer,  and  disappears  for  the  most  part  when  the  temperature  of  the 
water  sinks  to  the  freezing-point.  Water,  by  filtration  through  finely  pow- 
dered charcoal,  may  be  almost  entirely  deprived  of  organic  impurities. 

•318.  Hard  and  Soft  Waters  — Water  is  familiarly  spoken  of  as 
hard  or  soft,  according  to  its  action  on  soap.  Those  waters  which  contain 
compounds  of  lime  or  magnesia  occasion  a  curdling  of  the  soap,  as  these  earths 
produce  with  the  fat  of  the  soap  a  substance  which  is  not  soluble  in  water. 
Soft  waters  do  not  contain  these  earths,  and  dissolve  the  soap  without  diffi- 
culty. Many  hard  waters,  become  softer  by  boiling,  in  which  case  the  carbonic 
acid  gas  which  holds  the  lime  and  magnesia  for  the  most  part  in  solution,  13 
expelled  by  heat,  and  the  mineral  substances  are  deposited  upon  the  interior 
of  the  boiler,  causing  a  "fur,"  "scale,"  or  incrustation. 

Soft  water,  or  that  which  is  free  from  dissolved  mineral 
matter,  possesses  a  greater  solvent  power  than  hard  water ; 
-therefore  it  is  most  suitable  for  washing  and  for  the  prep- 
aration of  solutions.  In  culinary  operations,  where  the 
object  is  mainly  to  soften  the  texture  of  animal  or  veget- 
able substances,  or  to  extract  from  them  and  present  in  a 


*  G  oitre  is  a  swelling  of  the  glands  of  the  neck,  and  cretinism  is  a  variety  of  idiotcy. 


QUESTIONS. — How  much  organic  matter  in  water  will  render  it  unsuitable  for  use? 
What  effect  is  magnesia  supposed  to  have  in  water?  What  in  general  is  the  cause  of  the 
earthy  taste  of  certain  waters  ?  How  does  the  organic  matter  contained  in  waters  vary  ? 
When  are  waters  said  to  be  hard,  or  soft?  What  occasions  the  incrustation,  or  scalfi, 
upon  the  interior  of  boilers  ?  What  is  said  of  the  solvent  action  of  hard  and  soft  waters? 
What  of  their  respective  application  for  culinary  operations? 


216  INORGANIC     CHEMISTRY. 

liquid  form  some  valuable  constituent,  as  in  the  prepara- 
tion of  soups,  tea,  coffee,  etc.,  soft  water  is  the  best.  In 
other  instances,  in  which  it  is  desired  to  cook  a  substance, 
and  not  to  dissolve  it  or  extract  its  juice,  hard  water  is 
preferable.  To  prevent  the  over-dissolving  action  of  soft 
water  in  cooking,  salt  is  frequently  added,  which  hardens 
it.* 

319.  Much  speculation  has  been  occasioned  by  the  circumstance  that  fresh 
•water  can  generally  be  obtained  by  excavating  for  a  few  feet  or  inches  on  low- 
sandy  beaches,  or  islands  in  close  proximity  to  the  sea,  and  also  by  the  oc- 
currence, on  many  of  the  low  coral  islands  of  the  Pacific,  of  fresh  water  springs 
which  ebb  with  the  tide.     The  explanation  of  these  facts  seems  to  be,  that 
the  fresh  waters  are  derived  from  rains,  and  being  lighter  than  the  salt  water 
of  the  ocean,  remain  suspended  in  the  sands,  resting  upon  the  denser  water 
beneath.     They  consequently  rise  and  fall  with  the  motion  of  the  tides.     It  is 
also  true  that  the  water  of  the  ocean,  by  nitration  through  sand,  is  deprived 
in  part  of  its  saline  constituents. 

320.  All  ordinary  water  contains  in  solution  air,  and  generally  a  portion  of 
carbonic  acid  gas.     The  quantity  of  these  gases  absorbed  by  water  varies 
with  its  temperature,  and  also  with  the  pressure  of  the  atmosphere — cold 
water  dissolving  and  retaining  a  larger  quantity  than  warm  or  tepid  water. 
"When  cold  waters  from  springs  or  fountains  are  exposed  to  warm  air,  they 
become  elevated  in  temperature,  and  the  gases  contained  in  them  escape,  ren- 
dering the  water  flat  and  insipid.     The  principal  agent  in  imparting  a  sparkle 
and  freshness  to  water  is  atmospheric  ah-,  and  not  carbonic  acid  gas,  as  is 
often  supposed  and  taught. 

Air  and  other  gases  existing  in  water  may  be  expelled  from  it  by  raising 
the  water  to  a  boiling  temperature,  or  by  removing  the  pressure  of  the 
atmosphere.  The  presence  of  air  in  water  may  be  beautifully  illustrated 
by  placing  a  vessel  of  spring-water  beneath  the  receiver  of  an  air-pump 


*  "  These  facts  explain  why  it  is  impossible  to  correct  and  restore  the  flavor  in  veget- 
ables that  have  been  boiled  in  soft  water  by  afterward  salting  them.  It  is  also  well 
known  that  peas  and  beans  do  not  boil  soft  in  hard  water.  This  is  owing  to  the  effect 
which  lime  exerts  in  hardening  or  coagulating  a  peculiar  substance  ("  casein"),  which 
abounds  in  these  seeds.  Onions  furnish  a  good  example  of  the  influence  of  quality  in 
water.  If  boiled  in  pure  soft  water,  they  are  almost  entirely  destitute  of  taste  ;  though 
when  cooked  in  salted  water,  they  possess,  in  addition  to  the  pleasant  saline  taste,  a  pe- 
culiar sweetness  and  a  strong  aroma ;  and  they  also  contain  more  soluble  matter  than 
when  cooked  in  pure  water.  The  salt  hinders  the  solution  and  evaporation  of  the  soluble 
and  flavoring  principles."  —  Youmarfs  Household  Science. 


QUESTIONS. — How  is  the  presence  of  fresh  water  in  close  proximity  to  the  sea  accounted 
for  ?  What  is  said  of  the  presence  of  air  in  water  ?  Why  are  waters  which  have  been 
heated  flat  and  insipid  ?  How  may  air  and  the  gases  contained  in  water  be  expelled  from 
it  ?  How  may  the  presence  of  air  in  water  be  demonstrated  ? 


HYDROGEN.  217 

(Fig.  105),  and  gradually  exhausting  the  air.     As  the  exhaus-       FIG.  105, 
tion  proceeds,  the  dissolved  air  escapes  so  rapidly  as  to  oc- 
casion the  appearance  of  ebullition. 

Fishes  and  other  marine  animals  are  dependent  upon  the  air 
which  water  contains  for  their  respiration  and  existence.  If 
we  place  a  fish  in  water  which  has  been  entirely  deprived  of 
air,  it  is  almost  immediately  suffocated.  This  fact  can,  if 
desired,  be  demonstrated  with  the  aid  of  an  air-pump.  The 
quantity  of  air  retained  by  water,  at  an  altitude  of  6,000  or 
8,000  feet,  owing  to  a  reduced  atmospheric  pressure,  is  two-thirds  less  than 
the  usual  proportion.  Hence  it  is  that  fishes  can  not  live  in  high  mountain 
lakes — the  amount  of  air  contained  in  the  waters  being  inadequate  for  their 
respiration. 

A  remarkable  evidence  of  design  on  the  part  of  Providence  in  supplying  the 
wants  of  marine  animals,  which  extract  the  oxygen  they  require  for  the  sup- 
port of  life  from  the  water  in  which  they  live,  would  appear  to  be  found  in  the 
circumstance  that  water  absorbs  oxygen  and  nitrogen — the  constituents  of  air 
— in  proportions  different  from  those  existing  in  the  atmosphere.  Thus,  ordinary 
air  contains  about  21  per  cent  of  oxygen,  but  air  which  exists  in  water  con- 
tains from  30  to  33  per  cent  Marine  animate,  therefore,  can  obtain  more 
easily  the  necessary  supply  of  oxygen  from  air  which  contains  one-third  of 
this  gas,  than  from  air  containing  but  one-fifth. 

It  has  also  been  recently  discovered  by  Dr.  Hayes,  that  the  water  of  the 
ocean  contains  more  oxygen  near  its  surface  than  at  a  depth  of  one  or  two 
hundred  feet  This  fact  has  probably  some  connection  with  the  comparative 
scarcity  of  animal  life  at  great  depths. 

When  water  is  in  contact  with  an  atmosphere  of  mixed  gases,  it  dissolves 
of  each  a  quantity  precisely  equal  to  that  which  it  would  have  dissolved  if  in 
contact  with  an  atmosphere  of  this  gas  alone. 

Absolutely  pure  water  can  only  be  obtained  by  repeated  distillations  in 
clean  vessels  of  hard  glass. 

321.  Solvent  Properties  of  Water,— The  solvent  prop- 
erties of  water  far  exceed  those  of  any  known  liquid. 

Most  bodies  are  more  soluble  in  hot  than  in  cold  water,  the  solubility  in- 
creasing with  the  temperature.  Among  the  few  exceptions  to  this  rule  may 
be  mentioned  common  salt,  the  solubility  of  which  is  nearly  the  same  at  all 
temperatures,  and  lime,  which  is  more  soluble  in  cold  than  in  hot  water. 

322.  Chemical  Properties   of   Water, — Water    is    the 
perfection  of  a  neutral  substance,  and  enters  into  combi- 


QUESTIONS. — What  relation  does  air  in  water  sustain  to  animal  life  ?  What  arc  illus. 
trations  ?  What  peculiarity  characterizes  the  air  contained  in  water  ?  What  is  the  con- 
dition of  air  at  the  surface  and  at  the  bottom  of  the  ocean  ?  In  what  manner  does  water 
absorb  different  gases  ?  How  may  absolutely  pure  water  be  obtained  ?  What  ia  said  of 
the  solvent  action  of  water  in  general  ?  What  of  the  chemical  properties  of  water  ? 

19 


218  INORGANIC     CHEMISTRY. 

nation  most  extensively  with  acids,  bases,  with  a  large 
proportion  of  the  salts,  and,  in  short,  with  most  bodies 
which  contain  oxygen. 

A  compound  of  water,  in  definite  proportions  with,  some 
other  substance,  is  termed  a  hydrate  ;  and  a  body  entirely 
free  from  water  in  combination  is  said  to  be  anhydrous. 

When  a  salt  simply  dissolves  in  water,  the  act  of  solution  is  uniformly  at- 
tended with  the  production  of  cold ;  but  when  water*  chemically  combines 
with  a  salt,  or  forms  a  definite  hydrate,  the  formation  is  always  attended  with 
heat ;  this  circumstance  indicates  an  essential  difference  between  solution  in 
water  and  chemical  combination  with  water. 

"  Slacked  lime"  is  a  familiar  example  of  a  hydrate.  When  water  is  added 
to  quick  lime,  it  rapidly  combines  with  it,  producing  great  heat,  and  a  chem- 
ical compound  results,  which  is  a  "hydrate  of  lime."  When  water  unites 
with  potash  and  soda  under  the  same  circumstances  the  chemical  union  be- 
tween the  two  substances  is  so  strong,  that  no  amount  of  heat  alone  is  sufficient 
to  separate  them.  So  also  when  an  acid  has  once  been  allowed  to  combine 
with  water  the  entire  separation  of  the  two  is  seldom  practicable,  unless  some 
base,  for  which  the  acid  has  a  greater  affinity  than  for  water,  be  presented  • 
in  such  a  case  the  base  displaces  the  water,  and  its  expulsion  by  heat  is  then 
easily  effected.  For  example,  suppose  that  sulphuric  acid  has  been  freely 
diluted  with  water:  upon  the  application  of  heat,  the  water  at  first  passes 
off  readily,  leaving  the  less  volatile  acid  behind.  By  degrees,  however,  it 
becomes  necessary  to  increaso  the  temperature  in  order  to  continue  the  dis- 
tillation of  the  water,  and  at  last  the  acid  begins  to  evaporate  also,  and  finally 
no  further  separation  can  be  effected,  as  when  the  temperature  rises  to  about 
620°  F.,  both  water  and  acid  distil  over  together.  It  is  found  on  analyzing 
the  water  when  it  has  reached  this  point,  that  the  liquid  contains  one  equiv- 
alent of  acid  and  one  of  water,  its  composition  being  represented  by  the  sym- 
bols S03,  HO.  If  to  this  concentrated  acid  an  equivalent  of  potash  be  added, 
the  water  is  easily  expelled,  and  an  equivalent  of  anhydrous  sulphate  of 
potash  (KO,  S03)  remains.  Yvrater,  when  it  thus  supplies  the  place  of  a  base 
in  combination  with  acids,  is  called  basic  water. 

323.  Peroxyd,  or  Binoxyd  of  Hydrogen,  sometimes 
called  oxygenated  water,  was  discovered  by  Thenard,  in 
1818.  It  contains  twice  as  much  oxygen  as  water,  and  is 
a  body  characterized  by  most  remarkable  properties. 

*  For  explanation  of  water,  of  crystallization,  deliquescence,  efflorescence,  etc.,  see  §§ 
Ci,  65,  66,  67,  pp.  48,  49. 

QUESTIONS What  is  a  hydrate?     When  is  a  body  said  to  be  anhydrous?     What  fact 

illustrates  the  difference  between  a  solution  in,  and  a  combination  with,  water  ?  What 
are  illustrations  of  water  in  combination  ?  When  is  water  said  to  be  basic  ?  "What  is 
said  of  tho  second  oxyd  of  hydrogen  ? 


NITKOGEN.  219 

It  is  formed  by  decomposing  peroxyd  of  barium  by  sulphuric  or  hydroflu- 
oric acids.  The  process,  however,  is  most  difficult  and  complicated. 

Peroxyd  of  Hydrogen  is  a  syrupy  liquid,  of  specific  gravity  T45,  transparent, 
colorless,  and  almost  inodorous,  but  possessed  of  a  most  nauseous  and  astrin- 
gent taste.  Although  it  differs  from  water  only  in  containing  an  additional 
equivalent  of  oxygen,  it  is  a  powerful  bleaching  agent ;  and  when  applied  to 
the  skin  for  any  length  of  time,  whitens  and  destroys  its  texture.  It  can  be 
preserved  only  at  a  temperature  below  59°  F.  Heat  rapidly  decomposes  it 
into  water  and  oxygen  gas,  and  at  a  temperature  of  212°  F.,  the  evolution 
of  gas  is  so  rapid  as  to  occasion  an  explosion.  The  mere  contact  of  carbon, 
and  of  many  of  the  metals  and  metallic  oxyds  also  occasions  its  instantaneous 
decomposition,  accompanied  by  an  explosion  and  evolution  of  light. 

The  known  properties  of  this  substance  render  it  highly  probable  that  it 
would  prove  most  valuable  in  its  application  to  art — as  a  bleaching  and  oxyd- 
izing  agent.  The  expense  and  difficulty  attending  its  preparation  have,  how- 
ever, thus  far  prevented  its  employment  for  any  practical  purpose. 

SECTION    IV. 

NITROGEN,     OR     AZOTE. 

Equivalent  14     Symbol  N.     Density  0-971. 

324.  History , — Nitrogen  was  first  recognized  as  a  dis- 
tinct element  by  Dr.  Rutherford,  of  England,  in  1772. 

Its  name  is  derived  from  the  Greek  virpnv,  niter,  and  yevvau,  I  form  (the 
generator  of  niter).  Lavoisier,  from  its  inability  to  support  life,  termed  it 
Azote  (from  a  privative,  and  £w??,  life). 

325.  Natural    History, — Nitrogen  is  one  of  the   most 
abundant  of  the  elements. 

As  a  constituent  of  the  inorganic  kingdom  of  nature,  we  find  it  in  the.  at- 
mosphere, of  which  it  constitutes  four-fifths;  in  ammonia;  in  bituminous  coal ; 
in  the  well-known  salts,  nitrate  of  potash  and  nitrate  of  soda  (niter,  saltpeter), 
and  in  many  other  mineral  compounds.  In  the  organic  kingdom,  nitrogen 
especially  characterizes  animal,  in  contradistinction  to  vegetable  products; 
nevertheless  it  is  found  in  the  latter,  but  in  small  quantities.  One-fifth  of  the 
weight  of  the  dried  flesh  of  animals  is  nitrogen.  Tho  plants  which  contain  it 
in  greatest  quantity  belong  to  the  orders  cruciferse  (turnips,  cabbages,  horse- 
radish, mustard),  and  fungaccae  (mushrooms,  etc.).  Inasmuch 'as  animals  con- 
tain so  much  nitrogen,  and  vegetables  so  little,  Berzelius  imagined  that  nitro- 
gen was  generated  in  some  unknown  way  by  the  animal  functions.  This 
idea,  however,  has  been  opposed  by  Liebig,  who,  with  the  majority  of  chemists, 
believes  that  the  nitrogen  existing  in  plants,  upon  which  all  animals  directly 

QUESTIONS.— How  is  it  formed  ?  What  are  its  properties  ?  Has  the  peroxyd  of  hydro- 
gen been  applied  to  any  practical  use  ?  What  is  the  history  of  nitrogen  ?  What  is  said 
of  its  distribution  in  nature  ?  What  plants  contain  it  in  greatest  abundance  ?  * 


220  INORGANIC     CHEMISTRY. 

or  indirectly  feed,  is  sufficient  to  account  for  the  large  quantities  of  that  element 
locked  up  in  the  tissues  of  animals.  It  is  yet,  however,  one  of  the  great 
unsettled  questions  in  chemistry,  and  also  in  agriculture,  -whence  plants  derive 
their  nitrogen ; — whether  from  the  soil  (from  manures  and  decaying  organic 
matter),  or  from  the  ah1  directly,  or  from  the  ammonia  contained  in  the  air. 

826.  Preparation. — The  usual  methods  of  obtaining  a 
supply  of  nitrogen  for  the  purpose  of  experiment  are  based 
upon  the  removal  of  oxygen  from  atmospheric  air — leaving 
the  nitrogen  isolated  or  alone. 

The  simplest  plan  consists  in  placing  a  few  fragments  of  phosphorus  in  a 
little  metallic  or  porcelain  cup,  which  is  floated  upon  the  surface  of  the  water 
FIG  106  of  a  Pneumatic  trough.     The  phosphorus  is  ignited,  and 

a  glass  jar  or  receiver,  filled  with  air,  is  then  inverted 
over  it,  with  its  lip  in  the  water.  (See  Fig.  106.)  The 
phosphorus  burns  at  the  expense  of  the  oxygen  in  the 
confined  air,  and  by  reason  of  its  great  affinity  for  oxy- 
gen, it  combines  with  every  portion  of  this  element  con- 
tained in  the  receiver,  leaving  the  nitrogen  compara- 
tively pure.  As  the  combustion  proceeds,  the  water  of 
the  pneumatic  trough  gradually  rises  in  the  jar  to  supply 
the  place  of  the  consumed  oxygen.  The  product  of  the  union  of  the  phosphorus 
and  the  oxygen  is  phosphoric  acid,  which  at  first  pervades  the  receiver  as  a 
dense  white  vapor,  but  after  a  little  time  is  absorbed  by  the  water. 

Alcohol,  ignited  in  a  little  cup,  may  be  substituted  in  the  place  of  phos- 
phorus in  this  experiment,  but  it  does  not  consume  the  oxygen  entirely,  and 
produces  also  a  certain  quantity  of  carbonic  acid. 

The  removal  of  oxygen  from  the  air  may  also  be  effected  more  slowly  in 
various  ways.  A  stick  of  phosphorus  introduced  into  a  jar  of  air  standing 
over  water,  will  slowly  absorb  the  oxygen,  and  in  two  or  three  days  about 
four  fifths  of  the  original  bulk  of  the  air,  consisting  of  nitrogen  nearly  pure, 
will  be  left.  Moistened  iron  filings  produce  a  similar  result,  the  metal  gra- 
dually becoming  oxydized,  as  is  seen  by  the  rusty  appearance  which  it  as- 
sumes. 

Nitrogen  may  also  bo  obtained  by  conducting  chlorine  gas  into  a  solution 
of  ammonia  ;*  by  exposing  muscle  (flesh)  to  the  action  of  nitric  acid  in  a  re- 
tort to  which  heat  is  applied ;  and  in  a  state  of  great  purity  by  passing  a  cur- 
rent of  air  through  a  tube  containing  copper  turnings  heated  to  redness ;  the 
oxygen  in  this  experiment  being  entirely  absorbed  by  the  copper  to  form 
oxyd  of  copper,  while  the  nitrogen  passes  off. 

327.  Properties . — Nitrogen  is  a  colorless,  tasteless,  and  odorless  gas, 


*  This  experiment  is  a  somewhat  dangerous  one.     (See  chloride  of  nitrogen.) 


QUESTIONS. — Is  it  known  in  what  manner  plants  obtain  their  nitrogen  ?  How  is  nitro- 
gen obtained  ?  Enumerate  some  of  the  methods  employed  ?  What  arc  the  physical  prop- 
erties of  nitrogen  ? 


NITROGEN.  221 

which  as  jot  has  resisted  every  effort  to  liquefy  it.  It  is  somewhat  lighter 
than  atmospheric  air,  having  a  specific  gravity  of  0*971  (air  =  I'OO). 

One  of  the  most  distinguishing  characteristics  of  nitrogen  is  its  inertness,  or 
"sluggishness;"  it  being,  so  far  as  chemical  properties  are  concerned,  in  strik- 
ing contrast  with  oxygen,  which  is  one  of  the  most  energetic  of  the  elements. 
It  is  neither  acid  or  alkaline,  and  neither  supports  combustion,  or  burns.  A 
burning  taper  is  instantly  extinguished  in  this  gas,  and  an  animal  immersed 
in  it  quickly  perishes;  not  because  the  gas  is  injurious,  but  for  want  of  oxy- 
gen, which  is  required  for  both  respiration  and  combustion.  It,  however, 
enters  into  the  lungs  with  every  act  of  inspiration ;  is  a  constituent  of  our  most 
nutritious  food,  and  a  necessary  component  of  the  animal  frame. 

Nitrogen  docs  not  unite  directly  with  any  other  single  element;  but  its 
combination  with  the  various  elements  all  result  from  the  agency  "  of  indirect, 
oblique,  or  circuitous  processes,  which  conditions  being  accorded,  we  fre- 
quently have  whole  classes  of  substances  springing  into  existence ;  whereas, 
Jh  the  case  of  hydrogen,  the  combining  tendency  is  satisfied  with  the  forma- 
tion of  only  one  or  two  compounds." — FARADAY. 

A  striking  illustration  of  the  non-combining  properties  of  nitrogen,  is  found 
in  the  fact,  that  no  less  than  six  tons  of  air  pass  through  an  average-sized 
iron  blast-furnace  every  hour,  during  which  transit  the  oxygen  part  of  the  ail 
is  most  active  in  forming  combinations,  while  the  nitrogen,  although  subjected 
to  precisely  similar  conditions  of  heat  and  contact,  emerges  as  it  entered,  un* 
combined. 

328.  Instability  of  Nitrogen  in  Composition, — Nitro- 
gen, of  aft  ponderable  substances,  appears  to  have  the  greatest  affinity  for 
heat,  and  when  in  combination,  constantly  tends  to  unite  with  it,  and  resume 
its  elementary  condition  of  a  gas.  In  consequence  of  this,  and  also  by  reason 
of  its  slight  affinity  for  the  other  elements,  the  compounds  of  nitrogen  are  re- 
markably unstable.  Many  of  them  are  decomposed  with  extreme  suddenness 
by  the  slightest  causes — the  nitrogen  being  disengaged  in  the  gaseous  form, 
and  often  producing  most  violent  explosions.  Most  of  the  explosive  sub> 
stances  known  are  compounds  containing  nitrogen  as  an  essential  constitu- 
ent ;  as,  for  example,  gunpowder,  gun-cotton,  fulminating  mercury  (percussion- 
cap  powder),  fulminating  silver,  etc. 

A  substance  known  as  the  iodide  of  nitrogen  strikingly  illustrates  by  its 
mode  of  preparation  the  peculiarly  indirect  processes  demanded  by  nitrogen 
for  calling  its  powers  of  combination  into  play,  and  by  its  character  when 
formed,  the  instability  of  the  same  element  when  forced  into  union  with  an- 
other body.  Iodide  of  nitrogen  is  a  simple  compound  of  iodine  and  nitrogen. 
These  two  elements  when  mixed  together  directly  manifest  no  disposition  to 
unite,  and  may  be  preserved  in  contact  unchanged  for  an  indefinite  period. 
But  when  nitrogen  is  brought  in  contact  with  iodine  by  an  indirect  process, 

QUESTIONS.— What  is  one  of  the  most  distinguishing  characteristics  of  nitrogen  ?  Illus- 
trate this.  What  is  said  of  the  combinations  of  nitrogen  ?  What  circumstance  illustrates 
the  non-combining  properties  of  nitrogen  ?  What  peculiarity  has  nitrogen  in  composition  ? 


222  -INOKGANIC    CHEMISTBT. 

as  when  a  strong  solution  of  ammonia  is  mingled  in  a  glass  vessel  with  a  satu- 
rated solution  of  iodine  in  alcohol,  combination  almost  immediately  ensues, 
and  a  black  powder,  iodide  of  nitrogen,  is  formed.  This,  after  standing  for 
about  a  quarter  of  an  hour,  is  separated  from  the  liquid  by  filtration,  washed 
in  the  filter  with  pure  water,  and  dried  by  exposure  to  the  air  in. a  cool 
situation.  As  thus  prepared,  it  is  one  of  the  most  explosive  substances 
known,  the  nitrogen  being  held  by  so  slight  an  excess  of  force,  that  the  merest 
friction  between  the  particles  of  the  compound  is  sufficient  to  shatter  it  into 
its  elements.  This  result  may  be  illustrated  by  a  variety  of  experiments.  A 
small  quantity  projected  upon  water  explodes  the  instant  it  strikes  its  surface ; 
the  same  result  attends  the  dropping  of  a  fragment  from  a  slight  elevation 
upon  a  hard  surface,  or  by  placing  a  small  quantity  upon  one  end  of  a  counter 
and  striking  the  other  end  with  a  hammer.* 

Nitrogen,  in  some  mysterious  way,  appears  to  be  associated  with  all  the 
higher  forms  of  animal  existence.  The  blood,  the  muscle,  the  brain,  the. 
nerves  of  animals,  all  contain  it  in  large  quantity,  and  these  substances,  of 
all  organic  compounds,  are  the  ones  most  susceptible  of  decomposition. 

Organic  bodies  which  contain  a  large  amount  of  nitrogen,  generally  emit  a 
most  offensive  odor  when  they  decay.  The  odor  occasioned  by  the  putre- 
faction of  a  dead  human  body,  which  is  rich  in  nitrogen,  is  one  of  the  most 
offensive  in  nature.  Plants  which  contain  this  element  in  considerable  quan- 
tity, as  the  cabbage  and  mushroom,  putrefy  with  an  animal  odor.  Sub- 
stances containing  nitrogen  also  emit  an  offensive  and  peculiar  odor  when 
burned;  as  for  example,  the  smell  of  burnt  hair,  leather,  flesh,  bones,  etc. 
This  odor  may  be  regarded  as  an  invariable  test  of  the  presence  of  nitro- 
gen. 

Nitrogen  constitutes  an  essential  element  of  many  of  the  most  valuable 
and  potent  medicines,  as  quinia  and  morphia,  and  also  of  some  of  the  most 
dangerous  poisons,  as  prussic  acid  and  strychnia. 

A  suspicion  has  always  existed  that  nitrogen  may  be  a  compound  body. 
One  circumstance  which  ha!  led  to  this  idea,  is  its  demeanor  as  respects  elec- 
tricity. Most  of  the  binary  compounds  yield  up  their  elements  in  obedience 
to  the  direction  of  this  force,  but  electricity  determines  no  liberation  of  nitro- 
gen from  any  of  its  combinations.  All  attempts,  however,  to  decompose  it 
have  failed,  and  its  position  among  the  elements  must  therefore  remain  undis- 
puted. 

*  Iodide  of  nitrogen,  prepared  as  above,  is  not  liable  to  explode  while  moist,  and  in 
very  small  quantities  may  be  used  without  danger.  For  the  purpose  of  experiment  mi- 
nute portions  of  it  should  be  taken  upon  the  point  of  a  penknife  blade,  or  upon  the  end 
of  a  glass  rod. 

QTTESTIONS. — Into  what  class  of  compounds  does  it  particularly  enter  as  a  constituent? 
What  characteristics  of  nitrogen  are  illustrated  by  the  compound,  iodide  of  nitrogen  ? 
What  is  said  of  nitrogen  in  the  animal  system  ?  What  circumstance  characterizes  the 
decay  of  bodies  rich  in  nitrogen?  What  is  one  of  the  tests  of  the  presence  of  nitrogen  in 
ft  body  ?  What  is  said  of  the  elementary  character  of  nitrogen  ? 


NITROGEN.  223 

THE  ATMOSPHERE. 

329.  History . — The  air  was  formerly  supposed  to  be  an  element,  but 
was  not  altogether  regarded  iu  the  light  of  a  material  substance.  The  posi- 
tion which  it  held  in  the  old  systems  of  philosophy  was  similar  to  that  as- 
signed to  light,  heat,  and  electricity  in  some  systems  of  the  present  day — a 
fluid  substance  without  weight,  form,  color,  or,  in  short,  any  of  the  ordinary 
attributes  of  matter. 

It  was  not  until  1673  that  it  was  even  suspected  that  airs,  other  than  at- 
mospheric air,  might  have  an  existence.  About  that  time  Robert  Boyle,  au 
English  chemist,  maintained  "that  some  solid  bodies  do,  in  certain  circum- 
stances, as  when  heated,  throw  off  artificial  airs  resembling  atmospheric  air 
in  thinness  and  elasticity,  as  well  as  in  dryness  and  permanency,  but  differing 
from  it  he  could  not  well  tell  how." 

In  the  beginning  of  the  17th  century  the  workmen  in  certain  German 
mines  were  molested  (as  miners  still  are)  by  certain  agencies,  some  of  which 
were  liable  to  suffocate  them  silently  but  summarily  (carbonic  acid),  whilo 
others  burned,  or  exploding,  blew  thorn  into  fragments,  (firerdamp  carburetted 
hydrogen).  Yon  Ilelmont,  the  old  alchemist,  explained  these  phenomena  by 
referring  them  to  the  agency  of  spirits,  the  guardians  of  the  mineral  treas- 
ures, whom  he  called  geists  (ghosts).  From  this  originated  the  English  word 
gas,  which  is  still  employed  to  designate  aeriform  substances. 

Torricelli,  a  pupil  of  Galileo,  first  proved,  in  1643,  that  atmospheric  air  pos- 
sessed weight ;  and  one  hundred  and  fourteen  years  afterward,  or  in  1757, 
Joseph  Black,  a  Scotch  chemist  of  Edinburgh,  first  discovered  and  collected 
in  a  separate  state  a  gas  other  than  atmospheric  air.  He  ascertained  that 
limestone  (chalk,  marble,  or  oyster-shells)  when  burned  in  a  kiln,  or 
heated  with  a  strong  acid,  parts  with  a  kind  of  air  in  which  no  animal  can 
breath  and  live.  This  gas  (which  we  now  call  carbonic  acid)  Black  termed 
fixed  air,  because  it  was  imprisoned  in  the  rock  until  the  furnace  or  the  acid 
extricated  it  from  its  fixture. 

This  discovery  was  one  of  the  greatest  that  has  ever  been  made  in  chem- 
istry, since  it  for  the  first  time  clearly  proved  that  there  may  exist  different 
kinds  of  airy  matter  (just  as  there  are  different  kinds  of  solid  and  liquid  sub- 
stances), differing  as  much  from  the  gas  of  the  atmosphere  as  oil  or  sulphuric 
acid  differ  from  water,  or  as  slate  or  marble  from  sandstone. 

Shortly  after  this  discovery  by  Black,  Dr.  Priestley  devised  the  pneumatic 
trough  (once  known  as  the  Priestleyan  trough)  and  by  so  doing  rendered  easy 
the  collection  and  handling  of  gaseous  substances.  He  also  discovered  and 
isolated  nine  different  gases,  and  among  them  oxygen.  Scheele,  working  in 
an  obscure  Swedish  town,  with  no  other  apparatus  but  phials  and  bladders, 
about  the  same  time  added  two  or  three  more  to  the  list.  Discoveries  of  the 

QUESTIONS How  was  air  regarded  by  the  ancients?  When  was  the  existence  of  sepa- 
rate gases  first  suspected  ?  What  was  the  origin  of  the  term  "gas  ?"  Who  first  demon- 
strated the  weight  of  air  ?  Who  first  collected  and  recognized  a  separate  gas  ?  What 
was  the  nature  of  Black's  discovery  ?  What  is  said  of  the  importance  of  this  discovery  ? 
What  discoveries  succeeded  that  made  by  Black  ? 


224  INORGANIC     CHEMISTRY. 

game  kind  then  took  place  in  rapid  succession  all  over  Europe.  Cavendish 
followed  with  hydrogenr -Rutherford  with  nitrogen,,  while  Lavoisier  overthrew 
the  great  old  doctrine  of  the  elementary  nature  of  air,  by  proving  that  it  con- 
sisted of  two  gases  mingled  in  unequal  proportions.* 

Within  a  comparatively  recent  period  it  has  been  admitted  as  a  fundamental 
principle  in  physical  science,  that  "  gases  are  merely  the  steams  of  liquids 
which  boil  at  immensely  low  points  of  temperature,  these  liquids  being  the 
liquefactions  of  solid  bodies  which  melt  at  temperatures  lower  still,  and  that 
therefore  there  may  be  no  end  to  the  number  of  the  kinds  of  gaseous  mat- 
ter, precisely  as  there  is  ao  known  limit  to  the  vast  variety  of  liquids  and 
solids." 

330.  Atmospheric  Air  consists  essentially  of  nitrogen 
and  oxygen  mixed  together  in  the  proportion  of  four  fifths 
by  volume  of  the  former  to  one  fifth  of  the  latter. 

More  correctly,,  the  composition  of  air  which  has  been  freed  from  the  pres- 
ence of  all  foreign  ingredients  may  be  represented  by  measure  and  weight  as 
follows : — 

By  -weight.          By  measure. 

Nitrogen 76-90  79-10 

Oxygen 23-10  20-90 

100-00  100-00 

In  addition  to  oxygen  and  nitrogen,  the  atmosphere  always  contains  small 
and  variable  proportions  of  carbonic  acid  gas  and  aqueous  vapor ;  and  very 
often,  minute  quantities  of  ammonia,  nitric  acidr  the  aroma  of  flowers,  and  va- 
rious other  organic  and  inorganic  products ; — in  short,  as  the  sea  contains 
traces  of  almost  every  thing  that  is  soluble,  so  the  air  contains  traces  of  almost 
every  thing  that  is  volatile. 

The  oxygen  and  nitrogen  existing  in  the  air  are  merely  intermingled,  and 
not  chemically  combined  with  each  other;  but  then*  relative  proportions 
never  vary.  This  has  been  proved  by  the  analysis  of  air  collected  upon  the 
summit  of  Mount  Blanc,  and  upon  the  Andes;  at  an  elevation  of  21,000  feet 
by  Guy  Lussac  in  a  balloon  ;  over  marshes ;  in  hospitals ;  over  deserts ;  and 
at  the  bottom  of  the  deepest  mines. 

The  quantity  of  carbonic  acio,  on  the  contrary,  being  much  influenced  by 
local  causes,  varies  considerably.  The  average  quantity  is  4.9  volumes  in 
10,000  of  air,  bat  is  observed  to  vary  from  6.2  as  a  maximum  to  3.7  as  a 
minimum  in  10,000  volumes.  Its  proportion  near  the  surface  of  the  earth  is 


*  The  experiment  by  which  Lavoisier  arrived  at  this  result  is  described  under  the 

head  of  Combustion. 

t 

QUESTIONS. — "What  is  now  understood  to  be  the  trne  nature  of  gases?  What  is  the 
composition  of  atmospheric  air  ?  In  what  condition  do  oxygen  and  nitrogen  exist  in  the 
*ir  ?  Are  the  proportions  of  those  two  gases  variable?  What  is  the  proportion  of  car- 
bonic acid  in  the  air  r  Under  what  circumstances  does  it  vary? 


NITROGEN,  225 

greater  in  stltntnei1  than  in  winter,  and  during  night  than  during  day.  It  ig 
also  rather  more  abundant  in  elevated  situations,  as  on  the  summits  of  high 
mountains,  than  in  plains )  this  is  probably  owing  to  an  absorption  of  the  gas 
near  the  surface  of  the  earth  by  plants  and  moist  surfaces.  An  enormous 
quantity  of  carbonic  acid  gas  is  discharged  from  the  elevated  cones  of  the  vol- 
canoes of  America,  which  may  partially  account  for"  the  high  proportion  of 
this  gas  in  the  upper  regions  of  the  atmosphere.  The  gas  emitted  from  the 
Volcanoes  of  the  Old  World  is  said  to  be  principally  nitrogen 

The  quantity  of  watery  vapor  contained  in  the  air  Varies  with  the  temper" 
nture  (§  141,  page  92),  It  seldom  forms  more  than  If  60th  or  less  than 
l-200th  of  the  bulk  of  the  air, 

Notwithstanding  the  difference  in  density  between  each  of  the  principal 
constituents  of  the  atmosphere— ^-nitrogen,  Oxygen,  carbonic  acid,  and  the 
Vapor  of  water—and  notwithstanding,  also,  the  absence  of  any  chemical 
union  between  them,  they  are  always,  through  the  action  of  the  law  of  the 
diffusion  of  gases  (§  51,  page  39),  found  uniformly  mingled  together".  The 
operations,  also,  of  combustion,  respiration,  vegetation,  and  the  like,  continu* 
ally  going  on  upon  the  earth's  surface,  remove  great  quantities  of  oxygen 
from  the  air,  and  substitute  a  variety  of  other  gases,  the  principal  of  which  is 
carbonic  acid ;  yet  so  beautifully  adjusted  is  the  balance  of  chemical  action 
in  nature,  that  no  perceptible  change  in  the  composition  of  the  atmosphere 
lias  been  observed  since  accurate  experiment  on  the  subject  was  first  eonv 
menced, 

Ammonia/  seems  to  be  an  almost  constant  constituent  of  the  atmosphere  in 
exceedingly  minute  quantity,  Recent  most-carefully  conducted  experiments 
by  M,  Ville  of  France,  fix  the  average  quantity  as  1  volume  in  28,000,000  of 
air.  Other  experimenters  have  deduced  a  much  greater  result. 

Nitric  acid  may  be  usually  detected  in  the  rain-water  obtained  during  a 
thunder*shower,  It  is  supposed  to  be  formed  by  the  union  of  the  oxygen, 
nitrogen,  and  aqueous  Vapor  of  the  air,  through  the  agency  of  electricity, 

Organic  matter  of  some  kind  is  almost  always  present  in  the  atmosphere  \ 
but  it  not  unfrequently  happens  that  chemical  tests  fail  to  detect  it,  when  the 
sense  of  smell  and  a  peculiar  effect  upon  the  human  constitution  give  abun- 
dant evidence  of  its  presence,  This  is  especially  true  of  the  odoriferous  mat- 
ters of  flowers,  and  the  miasnlata  of  marshes,  Dew  collected  over  rice-fields 
often  contains  so  much  decomposing  organic  matter,  as  to  become  putrid  after 
standing  for  a  short  time,  Exposure  to  the  night  air  of  these  localities  in  the 
hot  season,  invariably  produces  in  the  Caucasian  race,  malignant  and  almost 
incurable  fevers. 

The  principal  office  which  nitrogen  appears  to  sustain  in  the  atmosphere, 
is  that  of  a  dilutent  of  the  oxygen,  If  the  quantity  of  oxygen  in  the  air  was 
increased  much  beyond  its  present  proportion,  the  inflammability  of  most  sub- 

QTTESTIONS.—  tfotf  does  the  quantity  of  aqueous  ^apof  vary  ?  What  is  said  of  the  uni- 
formity of  the  condition  of  the  atmosphere  ?  What  of  the  ammonia  of  the  atmosphere  ? 
What  of  nitric  acid  ?  What  of  organic  matter  7  What  office  does  nitrogen  appear  to 
sustain  in  the  atmosphere? 

10* 


INORGANIC    CHEMISTRY. 


stances  would  be  greatly  augmented;  and  the  functions  of  life  would  be 
called  into  such  rapid  action  as  to  soon  exhaust  the  powers  of  the  system. 
Nitrogen  being  the  most  indifferent  of  all  substances,  and  wanting  in  any 
poisonous  qualities,  dilutes  the  too  active  oxygen,  and  prolongs  its  action 
upon  the  system,  in  the  same  Way  as  water  dilutes  and  diminishes  the  stim- 
ulating action  of  spirituous  liquors.  Eecent  researches  have  also  rendered  it 
probable  that  the  nitrogen  of  the  aif  discharges  an  important  office  in  respir- 
ation, by  preserving  the  volume  and  tension  of  the  cells  and  extreme  tubes 
of  the  lungs. — PKOF.  MOITLTRIE. 

Oxygen  is  strikingly  magnetic ;  nitrogen  is  singularly  the  reverse ;  and 
the  atmosphere,  a  mixture  of  both,  is  nearly  neutral  as  respects  magnetism  in 
all  its  relations  to  matter, 

Another  illustration  of  the  adaptation  of  nitrogen  to  its  atmospheric  func- 
tions is  to  be  found  in  its  specific  gravity,  or  density,  which  is  nearly  the 
same  as  that  of  its  associated  oxygen.  Had  there  been  any  great  difference 
in  this  respect,  the  tendency  of  the  two  gases  would  have  been  toward  sep- 
aration, and  this,  notwithstanding  the  influence  of  the  law  of  diffusion. 
Again,  as  the  atmosphere  is  now  constituted,  there  exists  a  permanency  of 
the  pitch  of  sound :  any  tone  being  once  generated,  remains  the  same  tone 
until  it  dies  away.  Its  degree  of  loudness  alters  in  proportion  to  the  distance 
of  the  listener  from  the  place  where  it  originated,  but  its  pitch — never.  If 
the  specific  gravity  of  oxygen  and  nitrogen  had,  however,  been  widely  dis- 
similar, there  would  have  been  a  difference.  No  permanency  of  tone  could 
then  have  been  depended  on,  and  the  pitch  of  every  original  note  would  have 
Varied  continually.  "All  the  studied  ar- 
rangement of  defined  notes,  which  constitutes 
the  art  of  music,  would  have  been  lost  to  us 
forever,  had  we  been  enveloped  in  such  an 
atmosphere."  These  facts  may  be  illustrated 
by  striking  a  sonorous  body  in  a  receiver 
containing  air,  and  afterward  in  one  contain- 
ing h}*drogen,  which  is  much  lighter  than 
air.  (See  Fig.  107.)  The  experiment  may  be 
varied  by  causing  a  tuning-fork  in  the  key 
C  to  vibrate  over  a  small  glass  jar,  which, 
When  made  to  resound,  emits  the  same  note, 
and  is  therefore  hi  union  with  the  fork.  If 
the  jar  be  now  filled  with  hydrogen,  and 
inverted,  to  prevent  the  escape  of  gas,  and 
the  fork  be  again  caused  to  vibrate  opposite 
its  mouth,  the  unison  is  destroyed,  and  the 
sound  is  no  longer  responsive  to  the  note  C. 


FiG.  107. 


QTTESTIONS. — What  is  said  of  the  magnetic  condition  of  the  atmosphere  ?  How  does  tho 
specific  gravity  of  nitrogen  adapt  it  to  its  condition  in  the  atmosphere  ?  What  experi- 
ments illustrate  this  ? 


NITROGEN. 


227 


331.  Analysis  of  Air . — The  proportions  of  oxygen  and  nitrogen  in 
the  atmosphere  are  determined  by  withdrawing  the  oxygen  from  a  measured 
portion  of  perfectly  dry  air,  through  the  agency  of  va- 
rious substances  which  absorb  it.  (See  §  326,  page  220.) 
A  stick  of  phosphorus  introduced  into  a  known  measure 
of  air  in  a  graduated  tube,  the  open  end  of  which  is  be- 
neath the  surface  of  water  (see  Fig.  108).  effects  a  com- 
plete absorption  of  the  oxygen  in  about  24  hours. 
The  water  rising  in  the  tube  indicates  a  diminution  of 
one  fifth  in  the  volume  of  the  air — or  what  is  the  same 
thing,  a  withdrawal  of  from  20  to  21  per  cent,  of  oxygen. 
The  carbonic  acid,  aqueous  vapor,  ammonia,  and  the 
occasional  constituents  of  the  atmosphere,  are  deter- 
mined by  passing  a  measured  quantity  of  air  through 
receptacles  containing  materials  which  absorb  and  retain 
them. 

The  arrangement  by  which  this  can  be  best  effected  is 
called  an  Aspirator.  It  consists  simply  of  a  tight  cask  of 
a  known  capacity,  filled  with  water,  and  provided  at 

•FlG   109  the  base  with  a  stop-cock. 

At  the  top  of  the  cask,  a 
tube,  or  series  of  tubes,  or 
other  vessels  are  fitted,  as 
is  represented  in  Fig.  109  ; 
one  filled,  for  example,  with 
pumice  stone  drenched  with 
strong  sulphuric  acid,  and 
another  with  caustic  potash. 
When  the  cock  of  the  vessel  is  opened,  and  the  water  allowed  to  flow  out,  its 
place  is  supplied  by  an  equal  volume  of  air,  which  flows  in  through  the 
tubes.  The  sulphuric  acid  absorbs  all  the  moisture  contained  in  the  air 
which  flows  over  it,  and  the  potash  all  the  carbonic  acid.  The  quantity 
of  air  that  passes  through  the  tubes  is  known  by  the  quantity  of  water 
that  flows  out  of  the  cask,  while  the  increased  weight  of  the  separate 
tubes  gives  the  total  amount  of  moisture  and  carbonic  acid  contained  in  such 
quantity.  —I 

332.  Compounds  of  Nitrogen  and  Oxygen, — Nitrogen 
unites  with  oxygen  to  form  five  distinct  compounds,  con- 
taining, respectively,  1,  2,  3,  4,  and  5  equivalents  of  oxy- 
gen, with  1  of  nitrogen. 

Their  names  and  chemical  constitution  are  thus  expressed : 


QUESTIONS. — How  is  air  analyzed?  How  are  the  carbonic  acid  and  aqueous  vapor  of  the 
air  determined  ?  What  is  an  aspirator  ?  How  many  compounds  of  oxygen  and  nitrogen 
exist? 


228  INORGANIC    CHEMISTRY. 

Composed  by  weight,  of 


Symbol. 


Protoxyd  of  nitrogen  (nitrous  oxyd) NO  14  nitrogen  -f  &  oxygen. 

Deutoxyd  of  nitrogen  (nitric  oxyd) NOa  14        "•        +16        "• 

Tsitrousacid NOs  14        "        -f24        " 

Hyponitric acid  (peroxyd of  nitrogen).. NO4  14        "        +32        "• 

Nitricscid r.NO&  14        "        +40        «• 

Three  of  these  compounds  are  acids ;  and  all  of  them  are  endowed  with 
qualities  so  marked,  so  powerful,  and  so  well  defined,,  that  the  original  attri- 
butes of  their  elements  are  entirely  lost. 

333.  Nitric  Acid,  N05. — Nitric  acid  is  the  most  import- 
ant of  all  the  combinations  of  nitrogen  and  oxygen,  and  is 
/the  source  from  whence  most  of  the  compounds  of  nitrogen 
are  generally  obtained. 

334.  History . — It  was  known  to  the  alchemists,  but  its  true  composition 
was  first  determined  by  Cavendish  in  1785.    The  name  formerly  applied  to  it, 
and  which  is  still  used  to  some  extent,  was  aquafortis. 

335.  Distribution . — Nitric  acid  occurs  in  nature  usually  in  combina- 
tion with  potash,  soda,  or  lime  in  the  soil,  especially  in  tropical  countries,  as 
in  some  parts  of  India  and  Peru.     The  compound  formed  with  potash  consti- 
tutes the  nitre  or  saltpeter  of  commerce.     In  the  desert  of  Atacama.  in  Chili 
and  Peru,  it  exists  in  vast  quantities  combined  with  soday  forming  nitrate  of 
soda,  which  salt  is  also  called  "•  Chilian  saltpetre,"  or  cubic  niter.     Nitric  acidr 
as  already  stated,  also  exists  occasionally  in  the  atmosphere,  especially  during 
and  after  the  occurrence  of  thunder-storms. 

336.  Preparation . — When  nitrogen  is  mixed  with  twelve  or  fourteen1 
times  its  bulk  of  hydrogen,  and  a  jet  of  the  mixed  gas  is  allowed  to  burn  in 
air,  or  in  oxygen,  the  water  formed  has  a  sour  taste  and  an.  acid  reaction  from 
the  formation  of  a  small  quantity  of  nitric  acid.    In  this  case  the  nitrogen 
"burns  by  reason  of  the  great  heat  developed  during  the  combustion  of  the  hy- 
drogen, and  the  nitric  acid  combines  at  once  with  the  water  formed,  which 
last  substance,  in  some  way  by  its  presence,  aids  the  operation.    It  was  from 
noticing  the  acidity  of  water  formed  by  the  combustion  of  hydrogen  in  airr 
that  Cavendish  was  led  to  institute  an  investigation  which  terminated  in  the 
discovery  of  nitric  acid.     He  mixed  together  the  two  gases,  oxygen  and  ni- 
trogen, in  a  close  tube,  over  a  solution  of  potash,  and  then  caused  them  slowly 
to  combine  by  passing  a  series  of  electric  sparks  through  the  mixture  for  sev- 
eral success ve  days.    At  the  conclusion  of  the  experiment,  the  glass- contained 
nitrate  of  potash  (saltpeter).     A  similar  result  will  "be  produced  if  a  number 
of  sparks  be  passed  from  an  electrical  machine,  throngh  air  between  two 
metallic  points,,  over  moistened  litmus  paper :  a  red  spot  will  be  produced 
upon  the  paper,  owing  to»  the  formation  of  nitric  acid  in  minute  quantity  by 
the  combination  of  oxygen  with  nitrogen. 

QUESTIONS.— Give  the  series.  What  is  said  of  nitric  acid?  What  of  its  history? 
What  of  its  distribution  in  nature  1  How  may  nitric  acid  be  formed  ?  What  circum- 
stances led  to  its  discovery  ? 


N  I  T  K  0  G  E  N  .  229 

For  all  practical  purposes,  nitric  acid  is  always  obtained  by  heating  one  of 
the  natural  compounds  of  nitric  acid  with  potash  or  soda  in  a  retort,  with  an 
equal  weight  of  strong-  sulphuric  acid.  The  nitric  acid  is  displaced  by  the 
sulphuric  acid,  and  distils  over,  being  much  more  volatile  than  the  sulphuric 
acid. 

This  process  may  be  easily  FIG.  110. 

illustrated  experimentally 
by  introducing-  into  a  glass 
retort,  Fig.  110,  equal 
weights  of  powdered  salt- 
peter and  strong  sulphuric 
acid.  The  retort  should  be 
supported  upon  a  thin  layer 
of  sand  contained  in  a  tin 
or  sheet-iron  vessel  (tech- 
nically termed  a  sand-bath), 
and  the  heat  supplied  by  an  ordinary  alcohol-lamp  •  a  flask  cooled  by  a  wet 
cloth,  or  placed  in  a  vessel  of  cold  water,  is  adapted  to  the  retort,  and  serves 
as  a  receiver.  During  tho  distillation  red  fumes  appear  in  the  retort,  arising 
from  a  partial  decomposition  of  the  nitric  acid  formed,  and  a  production  of 
Borne  of  the  lower  oxyds  of  nitrogen.* 

On  a  large  scale,  iron  retorts  coated  on  the  inside  with  fire-clay  are  cm- 
ployed.  The  chemical  reaction  involved  in  this  process-  may  be  represented 
as  follows : 

KO,  JsT05+S03==E:Or  SOs+NOs. 

Or  sulphuric  acid  and  nitrate  of  potash  give  nitric  acid  and  sulphate  of 
potash, 

337.  Properties . — Nitric  acid,  when  pure  and  in  a  concentrated  state, 
is  a  colorless,  limpid,  fuming  liquid,  powerfully  corrosive  and  intensely  acid. 
As  found  in  commerce,  it  is  never  pure,  and  is  of  a  golden-yellow  color.  It 
is  the  highest  oxyd  of  nitrogen  known  to  exist,  and  has  a  specific  gravity 
of  1*52  (water  —  1).  Anhydrous  nitric  acid,  or  nitric  acid  without  water 
combined  with  it,  can  be  prepared  by  a  most  carefully  conducted  chemical 
process ;  but  under  all  ordinary  circumstances  it  contains  a  certain  proportion 
of  water ;  its  constitution  being  represented  by  the  formula  NOs,  HO,  In  the 
most  concentrated  state  in  which  it  can  be  used,  it  consists  of  54  parts-  real 
acid  and  9  of  water, 

Xitric  acid  is  very  readily  decomposed,  and  mere  distillation  causes  a  par- 
tial decomposition.  Exposure  to  light  produces  a  similar  result,  oxygen  and 


*  The  retort  generally  breaks  at  the  conclusion  of  this  process  from  the  crystallization 
of  the  sulphate  of  potash  formed,  but  it  may  be  saved  by  adding  to  it,,  when  partially 
cooled,  a  small  quantity  of  warm,  water. 


QUESTIONS. — How  is  it  practically  prepared  ?  What  is  the  chemical  reaction  involved" 
in  the  practical  production  of  nitric  acid  ?  What  are  the  properties  of  nitric  acid  ?  Does 
it  exist  apart  from  water  ?  Is  nitric  acid  easily  decomposed  1  What  effect  has  light  upon:  it  ? 


230  INORGANIC     CHEMISTRY. 

some  of  the  lower  oxygen  compounds  of  nitrogen,  which  produce  discolora- 
tion, being  evolved — sometimes  in  quantity  sufficient  to  expel  the  stopper  of 
a  bottle.  In  its  concentrated  form  it  begins  to  boil  at  184°  F.,  and  freezes 
at  about  —  40°  F. 

338.  Chemical  Action  of  Nitric  Acid  • — Nitric  acid  is  one  of 
the  very  strongest  acids,  and  ranks  next  to  sulphuric  acid.  It  attacks  most 
inorganic  substances,  and  all  living  tissues.  It  turns  wool,  feathers,  the  skin, 
and  all  animal  matters  containing  albumen,  a  bright  yellow  color ;  the  orange 
patterns  upon  woolen  table-cloths  are  produced  by  means  of  it.  In  medicine 
it  is  not  unfrequently  used  as  a  powerful  cauterizing  agent. 

The  effect  of  concentrated  nitric  acid  upon  animal  tissues  may  be  illus- 
trated by  applying  a  drop  to  a  piece  of  parchment,  which  immediately  be- 
comes stained  and  shrivelled.* 

The  action  of  nitric  acid  on  vegetable  colors  may  also  be  illustrated  by  the 
following  experiment: — Color  some  water  blue  in  a  test  tube  with  a  solution 
~}/  of  indigo,  and  add  to  it  on  boiling,  a  drop  of  nitric  acid ;  the  blue  color  will 
almost  immediately  disappear,  f 

Nitric  acid,  when  in  its  state  of  highest  concentration,  exerts  no  violent 
action  upon  certain  organic  substances,  such  as  woody  fibers,  starch,  etc.,  but 
unites  with  them  to  form  most  singular  compounds.  Cotton  fibers  immersed 
in  it  for  a  few  moments  and  then  carefully  washed  in  water,  are  converted 
into  a  violently  explosive  substance.  (See  gun-cotton.) 

Commercial  nitric  acid  will  completely  dissolve,  in  the  cold  and  without 
odor,  a  little  less  than  its  own  weight  of  flesh  and  bone  (beef),  in  a  space  of 
time  varying  from  three  to  five  hours.  The  action  of  nitric  acid,  however, 
upon  organic  substances  and  the  metals  is  exceedingly  different  at  different 
degrees  of  concentration. 

Nitric  acid  very  readily  parts  with  a  portion  of  its  oxygen  to  the  metals 
and  to  combustible  bodies,  and  is  therefore  one  of  the  principal  agents  made 
use  of  in  chemistry  for  causing  such  substances  to  assume,  or  pass  into  a  state 
of  oxydation. 

If  nitric  acid  be  dropped  upon  hot  finely  powdered  charcoal,  the  charcoal 
burns  vividly ;  if  mixed  with  a  little  oil  of  vitriol,  and  poured  upon  oil  of  tur- 
pentine, it  occasions  an  explosive  combustion.  Phosphorus  is  readily  ignited 

*  It  is  an  extraordinary,  very  cruel,  and  too  common  experiment  made  by  physiologists 
to  illustrate  what  they  are  pleased  to  call  a  power  of  vital  contractility  under  the  influ- 
ence of  a  stimulus,  by  touching  with  a  glass  rod  dipped  in  nitric  acid,  the  heart  of  a  living 
rabbit.  In  an  instant  the  heart  shrivels  and  contracts  to  one  third  its  original  size.— 
FABADAY. 

t  Indigo  solution— a  most  useful  chemical  reagent— may  be  easily  formed  by  pulver- 
izing a  small  quantity  of  indigo,  and  forming  a  thin  paste  of  it  with  strong  sulphuric 
acid.  After  a  few  days  add  water,  and  a  deep  blue  liquid,  solution  of  indigo,  is  obtained. 

QTTESTIONS.— What  are  its  freezing  and  boiling  points  ?  What  is  said  of  its  chemical 
character  ?  How  may  the  action  of  nitric  acid  upon  animal  tissues  be  illustrated  ?  How 
its  action  upon  vegetable  colors?  How  upon  vegetable  fibers?  How  is  nitric  acid  able 
to  produce  oxydation  ? 


NITROGEN.  231 

by  throwing  it  upon  strong  nitric  acid.  This  experiment  is  a  somewhat  haz- 
ardous one,  and  particles  of  phosphorus  scarcely  larger  than  the  head  of  a  pin 
Bliould  alone  be  employed, 

339,  The    Action    of   Nitric    Acid    upon    t  h  c  M  c  t  a  1  s  is  in- 
structive, and  serves  to  illustrate  the  manner  in  which  metallic  bodies  com- 
bine with  the  acids  generally,     The  metals  will  enter  into  direct  combination 
with  many  of  the  simple  non-metallic  bodies.     Thus  antimony  will  unite  with 
chlorine,  iron  with  oxygen,  and  copper  with  sulphur ;  but  no  metal  will  unito 
directly  with  an  acid.     In  order  that  combination  between  them  should  oc- 
cur, it  is  necessary  that  the  metal  should  be  in  the  form  of  an  oxyd.     This 
oxydation  may,  however,  be  effected  afc  the  same  time  that  the  acid  is  pre- 
sented to  the  metal,  and  the  formation  of  the  oxyd  and  its  solution  in  the 
acid  may  appear  to  occur  simultaneously.     Zinc,  for  example,  does  not  unito 
as  zinc  with  sulphuric  acid;  but  when  this  metal  is  placed  in  dilute  sulphuric 
acid,   the  oxygen  is  supplied  from  the  water  contained  in  it,  which  is  de- 
composed ; — oxyd  of  zinc  is  produced  and  is  immediately  dissolved  by  the 
acid,   whilst  the  hydrogen  escapes  in  the  gaseous  form.     When  a  metal, 
such  as  copper  or  silver,  is  dissolved  by  nitric  acid,  a  preliminary  oxydation 
is  equally  necessary ;  but  owing  to  the  facility  with  which  nitric  acid  is  de- 
composed, this  oxydation  is  usually  effected  by  depriving  tho  acid  of  a  por- 
tion of  its  oxygen,  it  being  more  readily  decomposed  than  water.     When  this 
takes  place,  a  part  of  the  products  of  the  decomposition  of  the  acid  escape 
into  the  air  in  the  form  of  deep  red  fumes  (see  hyponitric  acid),  while  the 
compound  of  the  metal  with  oxygen  dissolves  in  another  portion  of  tho  acid 
which  has  not  undergone  decomposition.     It  is  through  this  peculiar  action 
of  nitric  acid  that  it  is  rendered  a  most  ready  and  powerful  solvent  of  most 
of  the  metals. — MILLER. 

340,  Salts    of   Nitric    Acid  .—The  salts  formed  by  the  union  of 
nitric  acid  with  the  bases  are  termed  nitrates,  and  are  especially  remarkable 
for  the  circumstance  that  they  are  soluble  in  water,     "When  tho  nitrates  are 
all  thrown  upon  glowing  coals  they  are  decomposed ;  and  by  reason  of  the  es- 
cape of  oxygen,  they  deflagrate,  or  burn  furiously  with  scintillations.     If  dis- 
solved in  water,  and  paper  be  moistened  with  tho  solution,  allowed  to  dry, 
and  then  burned,  the  peculiar  combustion  characteristic  of  touch-paper  will 
be  produced.     This  property  is,  however,  exhibited  by  the  salts  of  some  other 
acids. 

Nitric  acid  is  a  substance  much  used  in  the  laboratory,  and  in  many  of  the 
operations  of  practical  art. 

341,  Protoxyd    of  Nitrogen,    NO  ; — Nitrous    Oxyd; — Exhilarating 
Gas. — This  gas  was  discovered  by  Priestley  in  1776,  but  its  properties  re- 
mained unknown  until  investigated  by  Davy,  in  1808.     Since  this  period,  a 
considerable  degree  of  popular  attention  has  always  been  bestowed  upon  it, 

QUESTIONS.—- Explain  the  action  of  nitric  acid  upon  the  metals,  and  the  principle  -which 
Buch  action  illustrates.  What  are  the  salts  of  nitric  acid  termed  ?  What  are  their  dis- 
tinguishing peculiarities?  When  and  by  whom  was  protoxyd  of  nitrogen  discovered  ? 


232  INOHGANIC    CHEMISTRY. 

in  consequence  of  the  remarkable  effects  which  it  produces  upon  the  animal 
system,  -when  taken  into  the  lungs, 

342.  Preparation , — Protoxyd  of  nitrogen  is  prepared  by  heating  the 
gait  known  as  nitrate  of  ammonia  in  a 
glass  flask,  furnished  with  a  perforated 
cork  and  a  bent  glass  tube,  over  a  spirit 
lamp.*  (See  Fig,  111.) 

Upon  the  application  of  a  moderate  tem- 
perature, the  salt  melts,  and  at  about  400° 
F.  apparently  begins  to  boil;  it  is,  how- 
ever,  in  reality  undergoing  a  process  of  de- 
composition, by  which  it  is  entirely  re- 
solved  into  gaseous  protoxyd  of  nitrogen 
and  steam  (water).  The  temperature  must 
be  very  carefully  watched,  and  not  allowed 
to  rise  so  high  as  to  occasion  white  vapors 
in  the  flask,  as,  in  such  case,  some  injurious 
products  may  be  formed.  The  gas  should 

be  collected  in  a  gasometer,  or  receiver  filled  with  water  of  a  temperature  of 
about  90 ;  cold  water  absorbing  considerable  quantities  of  it.  It  is  also  ad- 
visable to  allow  the  gas  to  remain  for  a  little  time  over  water  before  attempt-- 
ing to  respire  it. 

The  reaction  which  takes  place  in  the  production  of  protoxyd  of  nitrogen 
may  be  explained  as  follows ;  Ammonia  is  a  compound  of  nitrogen  with  hy- 
drogen. "When  the  nitrate  of  ammonia  is  heated,  the  hydrogen  of  the  am- 
monia combines  with  a  part  of  the  oxygen  of  the  nitric  acid  to  form  water, 
whilst  the  nitrogen  of  the  ammonia  at  the  same  time  becomes  oxydized  at  the 
expense  of  another  part  of  the  oxygen  of  the  nitric  acid.  The  result  is,  that 
the  whole  of  the  nitrogen,  both  of  the  nitric  acid  and  of  the  ammonia,  is  lib- 
erated in' the  form  of  protoxyd  of  nitrogen,  thus : 

Nitrate  of  ammonia.  Protox,  nitrog.    Water, 


NH3,  N0«,  HO  become*  2  NO +  4  HO 

An  ounce  of  nitrate  of  ammonia  will  furnish  about  500  cubic  inches  of  this 
gas. 

343.  Properties , — Protoxyd  of  nitrogen  is  a  transparent,  colorless 
gas,  with  a  sweetish  smell  and  taste.  It  is  a  heavy  gas,  its  specific  gravity 
being  T52,  or  nearly  the  same  as  that  of  carbonic  acid.  It  supports  the  com- 
bustion of  many  bodies  with  nearly  the  same  energy  and  brilliancy  as  pure 

*  Nitrate  of  ammonia  is  a  -white  crystalline  salt,  which  can  fee  cheaply  purchased  of 
dealers  in  chemicals,  or  can  he  easily  made  hy  neutralizing  dilute  nitric  acid  by  carbonate 
of  ammonia.  In  preparing  exhilarating  gas,  not  less  than  6  or  8  ounces  should  be  ttsed. 


QUESTIONS. — How  is  it  prepared?    What  is  the  chemical  reaction  involved  %i  the  pro- 
cess ?     What  are  its  properties  ? 


NITROGEN".  233 

oxygen  •  and  when  mixed  with  an  equal  bulk  of  hydrogen,  forms  an  explosive 
mixture.  It  is,  however,  easily  distinguished  from  oxygen  by  its  ready  solu- 
bility in  cold  water,  which  dissolves  nearly  its  own  volume  of  the  protoxyd 
of  nitrogen. 

Under  a  pressure  of  50  atmospheres  at  45°  F.,  it  is  reducible  to  a  clear 
liquid,  which,  at  a  temperature  of  about  150  degrees  below  zero,  freezes  into 
a  beautiful  transparent  crystalline  solid.  By  mixing  the  liquid  protoxyd  with 
another  very  volatile  substance,  the  bisulphide  of  carbon,  and  allowing  the 
mixture  to  evaporate  in  vaccuo,  M.  JSTatterer,  a  few  years  since,  obtained  a 
reduction  of  temperature  which  he  estimated  at  220  degrees  below  zero  ; — a 
lower  point  than  has  been  hitherto  attained  to  by  any  other  process. 

Protoxyd  of  nitrogen,  if  quite  pure,  or  merely  mixed  with  atmospheric  air, 
may  be  respired  for  a  few  minutes  without  inconvenience  or  danger.  It  then 
produces  a  singular  species  of  transient  intoxication,  "  attended  in  many  in- 
stances with  an  irresistible  propensity  to  muscular  exertion,  and  often  to  un- 
controllable laughter ;  hence  the  gas  has  acquired  the  popular  name  of  exhil- 
arating or  laughing-gas.  Different  individuals  are  affected  in  different  degrees 
and  in  various  ways,  according  to  the  temperament  of  each.  In  plethoric? 
persons,  where  there  is  any  tendency  to  over-active  circulation  through  the 
brain,  the  experiment  is  not  a  safe  one.  The  intoxicating  effects  pass  off  in 
a  few  minutes,  and  frequently  no  recollection  of  what  has  passed  is  retained, 
and  no  lassitude  is  perceived  after  the  extreme  exertion." — MILLER.  The  gas 
should  be  inhaled  from  a  large  bladder  or  gas-bag,  through  a  tube  of  an  inch 
internal  diameter. 

An  animal  entirely  immersed  in  this  gas  soon  dies  from  the  prolonged  ef- 
fects of  the  intoxication. 

The  idea  that  anassthesis,  or  insensibility  to  pain  during  surgical  operations, 
might  be  occasioned  by  the  inhalation  of  gases,  appears  to  have  been  first  en- 
tertained by  Dr.  Horace  Wells,  of  Hartford,  Conn.,  from  observing  the  action 
of  protoxyd  of  nitrogen  upon  the  animal  system ;  and  he  succeeded  in  pro- 
ducing, by  means  of  it,  the  same  effects  which  are  now'accom-  ^ 
plished  by  the  agency  of  chloroform  and  ether. 

344.  Deutoxyd  of  Nitrogen,  NO*:  Bin&xyd  of  Ni- 
trogen, or  Nitric  Oxyd. — This  gas  is  easily  prepared  by  pouring 
nitric  acid  upon  clippings  or  turnings  of  copper,  contained  in 
a  flask  with  a  little  water.  As  no  heat  is  required,  the  double- 
tubed  hydrogen  gas  apparatus  may  be  employed,  (See  Fig. 
112.)  At  the  commencement  of  the  action,  the  flask  becomes 
filled  with  deep-red  fumes,  but  if  the  gas  be  collected  over 
water  it  will  be  found  to  be  colorless. 

The  chemical  action  involved  in  the  production  of  nitrous 
oxyd,  by  this  process,  is  as  follows :  The  copper  takes  oxygen  from  one  por- 

QTTESTIONS. — How  is  it  distinguished  from  oxygen  ?  What  effect  has  cold  or  pressure 
upon  it  ?  What  effect  does  protoxyd  of  nitrogen  produce  upon  the  system  •when  inhaled  ? 
What  discovery  was  first  suggested  by  the  action  of  this  gas  on  the  system  ?  How  is 
nitric  oxyd  prepared  ?  What  is  the  chemical  action  involved  ? 


234  INORGANIC    CHEMISTEY. 

tion  of  the  nitric  acid  and  becomes  oxyd  of  copper,  which  combines  with  an- 
other portion  of  acid  remaining  undecomposed,  and  forms  the  nitrate  of  cop- 
per, the  solution  of  which  is  of  a  blue  color.  That  part  of  the  nitric  acid  which 
is  decomposed,  loses  three  equivalents  of  oxygen,  which  are  taken  up  by  the 
copper  ;  the  remaining  two  equivalents  of  oxygen  united  with  the  nitrogen 
appear  as  the  gas,  thus  : 

Copper.        Nitric  acid.  Nitrate  copper.         Nitric  oxyd. 

(CuuO,  N05)-|-N02 


345.  Properties  ,  —  Nitric  oxyd  is  a  colorless  gas,  which  is  but  slightly 
absorbed  by  water.  It  is  perfectly  irrespirable,  and  excites  a  violent  spasm 
of  the  throat  when  an  attempt  is  made  to  respire  it.  Sir  Humphrey  Davy,  in 
his  experiments  upon  the  respiration  of  the  protoxyd  of  nitrogen,  attempted 
to  inhale  this  gas,  but  the  result  was  nearly  fatal,  and  would  have  been  quite 
so,  had  not  the  glottis  contracted  spasmodically,  and  thus  prevented  its  pas- 
sage into  the  lungs. 

Most  burning  bodies,  when  immersed  in  this  gas,  are  extinguished  by  it, 
although  it  contains  half  its  weight  of  oxygen.  If  phosphorus  and  charcoal, 
however,  in  a  state  of  ignition,  be  introduced  into  it,  the  heat  they  evolve 
effects  the  decomposition  of  the  gas,  and  the  combustion  continues  with  great 
brilliancy  through  the  agency  of  the  liberated  oxygen. 

The  most  remarkable  property  of  nitric  oxyd  appears  to  be  its  great  attrac- 
tion for  oxygen.  "When  mixed  with  oxygen,  or  any  gas  containing  oxygen 
(atmospheric  air),  dense  red  fumes  are  produced,  which  are  soluble  in  water, 
and  produce  an  acid  liquid.  In  this  way  nitric  oxyd  may  be  used  as  a  test 
to  demonstrate  the  presence  of  uncombined  oxygen  in  a  gaseous  mixture. 
Experimentally  this  action  may  be  demonstrated  as  follows  :  Partially  fill  a 
tall  glass  jar  or  bottle  with  nitric  oxyd,  over  a  pneumatic  trough  ;  and  then 
by  lifting  the  end  of  the  jar,  admit  a  few  bubbles  of  atmospheric  air,  or  pure 
oxygen.  In  an  instant,  deep  blood-red  fumes  will  fill  the  vessel,  and  much 
heat  will  be  generated.  By  agitating  the  contents  of  the  jar  with  water,  the 
red  vapors  are  rapidly  absorbed,  and  the  experiment  may  be  several  times 
repeated,  with  the  remaining  portions  of  the  gas. 

Nitrous  oxyd  has  never  been  liquefied. 

/  346.  Nitrous  Acid,  IV  03.  Hyponitrous  Acid,  —  The  third  compound 
of  nitrogen  with  oxygen  is  a  brownish  red  vapor  at  ordinary  temperatures, 
and  a  volatile  green  liquid  at  a  temperature  0°  F.  It  is  formed  by  mixing 
4  volumes  of  nitrous  oxyd  with  1  volume  of  oxygen,  both  in  a  perfectly  dry 
state.  It  unites  with  bases  to  form  salts,  which  are  called  nitrites. 
f  347.  Hypo  nitric  Acid,  N04.  Peroxyd  of  Nitrogen.  —  The  red  fumes 
which  appear  in  mixing  nitrous  oxyd  with  oxygen,  or  atmospheric  air,  con- 

QUESTIONS.  —  What  are  its  properties  ?  How  does  it  act  upon  combustibles  ?  What  is 
the  most  remarkable  characteristic  of  nitric  oxyd  ?  How  may  it  be  illustrated  ?  What 
is  the  physical  condition  of  nitrous  acid  ?  How  is  it  prepared  ?  What  is  said  of  hyponi- 
tricacid? 


CHLORINE. 


235 


gist  mainly  of  hyponitric  acid.     It  may  be  formed  in  a  state  of  purity,  by 
mixing  4  volumes  of  nitrous  oxyd  with  2  volumes  of  oxygen. 

The  compounds  of  nitrogen  with  hydrogen,  carbon,  and  other  non-metallic 
elements,  will  be  considered  in  subsequent  sections,  j 

SECTION     Y. 

CHLORINE. 

Equivalent,  35'5.     Symbol,  Cl.     Density,  2'47. 

348.  History , — -This  substance  was  discovered  by  Scheele 
in  1774,  and  called  by  him  dephlogisticated  marine  acid. 

It  was  universally  regarded  as  a  compound  body  until  1808,  when  Davy 
established  its  elementary  character,  and  on  account  of  its  yellowish-green 
tint,  gave  it  the  appellation  of  chlorine  (from  ^/Iwpof,  green). 

349.  Natural  History  and  Distribution.  —  Chlorine  is  a 
principal  member  of  a  small  natural  group  of  four  closely-allied  elementary 
bodies,  viz.,  chlorine,  iodine,  bromine,  and  fluorine,  which  differ  in  many  re- 
spects from  all  the  other  elements.  They  are  characterized  by  a  remarkable 
indifference  for  each  other,  and  for  an  intense  affinity  for  other  substances  at 
ordinary  temperatures — an  affinity  so  general  as  to  preclude  the  possibility  of 
any  member  of  the  class  existing  in  a  free  and  uncombined  state  in  nature. 


Collectively  they  are  termed  the  Halogens,  from  the 
circumstance  of  their  forming  with  the  metals  saline 
compounds  resembling  common  salt. — Haloid  salts. 
(See  §  271.) 

Chlorine  united  with  other  elements  is  a  large  con- 
stituent both  of  the  inorganic  and  organic  kingdoms. 
The  great  magazine  of  it  in  nature  is  rock,  or  common 
salt,  which  is  a  compound  of  chlorine  and  the  metal 
sodium.  Combinations  of  it  also  with  other  substances 
in  the  mineral  kingdom  are  not  unfrequent.  In  the  or- 
ganic kingdom  it  is  found  as  a  constituent  of  both  an- 
imals and  vegetables ;  existing  in  the  greater  number 
of  animal  liquids,  and  in  various  fluids  and  secretions 
of  plants. 

350.  Preparatio  n. — Chlorine  is  most  easily  pre- 
pared by  pouring  strong  hydrochloric  (muriatic)  acid 
upon  pulverized  binoxyd  of  manganese  contained  in  a 
glass  retort  or  flask  (arranged  as  in  Fig.  113),  and  ap- 
plying a  gentle  heat  from  a  spirit-lamp.  The  propor- 
tions which  give  tho  best  result  are,  one  part  by  weight 


FIG,  113. 


QUESTIONS. — How  is  it  prepared  ?  Give  the  history  of  chlorine.  To  what  other  ele- 
ments is  chlorine  allied  ?  What  are  the  characteristics  of  these  associated  elements  ? 
What  designation  is  given  to  them  as  a  class  ?  What  is  said  of  the  distribution  of  chlor- 
ine in  nature  ?  How  is  it  prepared  ? 


236  INORGANIC     CHEMISTRY. 

of  binoxyd  of  manganese,  and  two  parts  by  weight  of  hydrochloric  acid.  Tho 
gas  may  be  collected  over  water,  or  more  conveniently  by  the  displacement 
of  air  in  a  dry,  narrow-necked  jar,  as  is  represented  in  Fig.  113.  The  green- 
ish color  of  the  chlorine  enables  the  operator  to  determine  when  the  receiver 
is  full.  By  closing  the  jars  with  glass  stoppers,  well  smeared  with  tallow,  the 
jf^as  can  be  preserved  unaltered  for  a  considerable  length  of  time.* 

The  chemical  reaction  which  takes  place  in  this  process  may  be  explained 
as  follows :  hydrochloric  acid  is  a  compound  of  hydrogen  and  chlorine ;  when 
mixed  with  the  binoxyd  of  manganese  in  the  proportion  of  2  equivalents  of 
the  former  to  1  of  the  latter,  double  decomposition  ensues: — water,  free 
chlorine,  and  a  chloride  of  the  metal  being  produced. 

Thus,—  Mn02-f-2HCl=MnCH-2HO-hCl. 

Three  ounces  of  powdered  binoxyd  of  manganese  with  half  a  pint  of  com- 
mercial muriatic  acid  diluted  with  3  ounces  of  water,  will  yield  between  three 
and  four  gallons  of  the  gas.  Care  should  be  taken  not  to  use  an  acid  more 
dilute  than  the  one  indicated,  lest  some  explosive  compound  of  chlorine  should 
be  generated. 

Chlorine  may  also  be  readily  obtained  by  distilling  a  mixture  of  4  parts  by 
•weight  of  common  salt,  1  part  of  binoxyd  of  manganese,  2  of  sulphuric  acid, 
and  2  of  water.  It  is  in  this  way  that  chlorine  is  prepared  in  enormous  quan- 
tities for  manufacturing  purposes ;  but  for  the  preparation  of  "  chloride  of 
lime,"  the  first  described  method  is  followed,  owing  to  the  fact  that  the  hy- 


*  The  following  memoranda  respecting  the  preparation  of  chlorine  are  worthy  of  atten- 
tion. The  process  should  always  be  conducted  in  a  well-ventilated  apartment,  altogether 
free  from  valuable  furniture,  and  especially  from  colored  curtains,  paper-hangings,  etc. — 
the  action  of  the  gas  being  most  destructive  of  the  color  and  texture  of  organic  compounds. 

Before  applying  heat  to  the  generating  flask,  the  operator  should  observe  whether  the 
interior  of  the  glass  has  become  thoroughly  wetted  by  the  acid,  or  whether  a  dry  spot 
still  remains.  If  the  latter  is  the  case,  all  heat  should  be  withheld  until  the  mass  by  agi- 
tation has  become  thoroughly  incorporated,  and  the  dry  spot  disappears.  If  this  precau- 
tion is  neglected,  a  fracture  of  the  retort  will  probably  take  place  on  the  application  of 
heat.  Most  authorities  recommend  the  collection  of  chlorine  over  warm  water,  inasmuch 
as  cold  water  absorbs  a  considerable  amount  of  the  gas.  This  plan  is  attended  with  the 
serious  disadvantage  of  causing  chlorine  to  enter  the  bottle  hot,  and  for  that  reason  rare- 
fied ;  so  that  when  it  cools  and  contracts,  the  stoppers  of  the  bottles  are  found  not  unfre- 
quontly  to  be  permanently  fixed.  Cold  water  should  be  employed,  and  except  it  be  agi- 
tated whilst  the  gas  is  passing  through  it,  so  little  of  the  chlorine  is  absorbed  that  the 
amount  of  loss  is  too  small  to  be  of  consequence. — FAEADAY. 

Every  care  should  be  taken  in  bottling  up  chlorine  for  preservation,  to  exclude  water  as 
much  as  possible,  inasmuch  as  under  the  agency  of  light,  water  and  chlorine  react,  form- 
ing hydrochloric  acid,  which  is  so  violently  absorbed  by  water,  that  the  stoppers  of  the 
chlorine  bottles  become  often  irremediably  fixed,  owing  to  external  pressure. — IBID. 

If  the  operator  during  the  preparation  of  chlorine  should  inadvertently  inhale  a  dis- 
agreeable quantity  of  the  gas,  the  most  effectual  relief  will  be  obtained  from  an  immediate 
application  of  ammonia  (smelling-salts)  to  the  nostrils,  or  from  inhaling  the  vapor  of  al- 
cohol or  ether. 

QUESTIONS. — What  precautions  are  to  be  observed  in  its  preparation?  What  is  the 
chemical  action  involved  in  this  process  ?  By  what  other  process  may  chlorine  be  pre- 
pared ?  For  what  practical  purposes  are  these  two  processes  applied  ? 


CHLORINE.  237 

drochloric  acid  Used  is  obtained  as  a  waste  product  in  the  manufacture  of 
^carbonate  of  soda  (soda-ash)  from  sea-salt.      >     ^P*»***» 

351.  Properties  , — Chlorine  is  a  dense,  heavy  gas,  of  a  greenish-yel- 
low color.     It  is  characterized  by  a  peculiar  suffocating  odor,  almost  intoler- 
able to  most  persons  even  when  greatly  diluted  with  air,  and  occasioning  a 
distressing  irritation  of  the  air-passages  of  the  throat,  attended  with  cough- 
ing.    Any  attempt  to  respire  the  gas  in  a  pure  form  would  probably  be  fatal, 
but  when  largely  diluted  with  air,  it  is  breathed  without  inconvenience  by 
workmen  in  manufacturing  establishments,  and  it  has  also  been  adopted  as 
a  remedial  agent  in  this  condition  with  benefit  for  pulmonary  diseases.     It 
should  not,  however,  be  used  for  this  latter  purpose  without  the  sanction  of 
a  medical  authority. 

Chlorine  is  one  of  the  heaviest  of  the  gases,  its  specific  gravity  being  2 '47 
(air  ==•  1).  tinder  a  pressure  of  4  atmospheres,  at  60°  F.,  it  condenses  to  a 
yellow  liquid,  of  specific  gravity  1*33,  which  remains  unfrozen  even  at  a  cold 
of—  220°  F. 

Cold  water  absorbs  about  twice  its  bulk  of  chlorine  gas.  This  solution, 
which  is  readily  formed  by  agitating  the  gas  and  the  water  together,  ac- 
quires the  color,  odor,  and  other  properties  of  chlorine,  and  is  much  used  for 
experimental  and  manufacturing  purposes  in  preference  to  the  pure  gas.  As 
it  is  slowly  decomposed  by  the  action  of  light,  it  should  be  preserved  in 
bottles  covered  with  paper,  or  in  a  dark  place. 

With  water  near  its  freezing  point  chlorine  combines  to  form  a  definite 
hydrate,  which  contains  10  equivalents  of  water  (Cl-f-10HO) ;  this  at  a  tem- 
perature of  32°  F.  freezes  and  forms  beautiful  yellow 
crystals.     If  these  crystals  be  hermetically  enclosed  FIG.  114. 

in  a  glass  tube  (see  Fig.  114),  they  will,  when  ex- 
posed to  a  gentle  heat,  liberate  free  chlorine ;  this 
prevented  from  expanding,  presses  upon  itself  to 
such  an  extent  that  a  portion  of  the  gas  liquefies, 

and  may  then  be  seen  in  the  tube,  floating  upon  the  water  which  is 
present.  This  process  furnishes  the  most  ready  way  of  obtaining  liquid 
chlorine. 

352.  Chlorine  is  a  supporter  of  combustion,  but  its  effects  are  strikingly 
different  from  those  manifested  by  oxygen.     It  does  not  combine  directly  with 
either  oxygen  or  carbon,  but  has  a  most  powerful  affinity  for  hydrogen  and 
the  metals.     Therefore,  bodies  rich  in  oxygen  and  carbon,  either  burn  indif- 
ferently in  chlorine  or  not  at  all,  as  in  the  case  of  charcoal  j  but  on  the  con- 
trary, bodies  rich  in  hydrogen,  together  with  many  of  the  metals,  burn  in  it 
with  great  brilliancy.     The  following  experiments  are  illustrative  of  these 
facts : 


QUESTIONS. — What  are  the  general  properties  of  chlorine  ?  Is  it  at  all  respirable  ? 
"What  is  the  density  of  chlorine?  Can  it  be  liquefied?  What  is  a  solution  of  chlorine? 
What  are  its  properties  ?  What  combination  does  chlorine  form  with  water  ?  How  may 
liquid  chlorine  be  prepared?  What  are  the  relations  of  chlorine  to  combustion  ? 


238 


INORGANIC     CHEMISTRY. 


A  piece  of  flaming  charcoal  plunged  into  a  vessel  of  chlorine  is  extinguished 
as  instantly  and  as  completely  as  if  plunged  into  a  vessel  of  water. 

"Wax  and  tallow  are  compounds  of  carbon  and  hydrogen.  If  a  lighted 
taper  be  immersed  in  a  jar  of  chlorine,  its  flame  is  extinguished ;  but  the 
column  of  oily  vapor  rising  from  the  wick  is  rekindled  by  the  chlorine ;  tho 
hydrogen  part  of  the  combustible  burning  with  a  dull  reddish  flame,  while 
the  carbon  is  separated  in  the  form  of  a  dense  black  smoke. 

Another  experiment  illustrates  the  same  action  in  a  more  remarkable  man- 
FIG.  115.  ner-  0^  °f  turpentine  is  a  liquid  exceedingly  rich  in  hy- 
drogen, and  also  in  carbon.  If  a  piece  of  paper  soaked  in 
it  be  fastened  to  the  end  of  a  rod  and  plunged  into  a  jar  of 
chlorine  (see  Fig  115),  the  chlorine  unites  with  the  hydro- 
gen so  readily  as  to  instantly  produce  spontaneous  combus- 
tion, while  the  carbon  is  separated  and  deposited  as  an 
abundant  soot. 

If  a  bit  of  ignited  phosphorus  be  immersed  in  a  jar  of 
chlorine,  as  is  represented  in  Fig.  116,  the  combustion  con- 
tinues, but  the  light  evolved  is  hardly  perceptible.  If  a 
piece  of  phosphorus  be  plunged  into  chlorine  without  ig- 
nition, it  inflames  spontaneously — a  result  which  does  not 
take  place  in  oxygen.  The  feeble  light  which  accompanies 
the  combustion  of  phosphorus  in  chlorine,  therefore,  can  not 
be  explained  by  reason  of  any  lack  of  affinity  FIG. 

between  these  two  substances,  but  it  is  due  to 
the  fact  that  the  immediate  products  of  the  com- 
bustion are  vaporous  or  gaseous,  and  are  not 
rendered  luminous  by  heating.  (See  Combustion.) 
Antimony  and  many  other  metals  finely  pow- 
dered, and  projected  into  a  vessel  of  chlorine,  take 
fire  and  produce  a  brilliant  combustion.  Thin 
sheets  of  copper  leaf,  attached  to  a  copper  wire, 
and  dipped  into  chlorine,  exhibit  the  same  phe- 
nomenon. 

353.  The  intense  affinity  which  chlorine  mani- 
fests for  hydrogen  is  one  of  the  most  remarkable 
characteristics  of  this  element,  and  is  the  property,  above  all  others,  which 
gives  to  chlorine  its  great  value  as  an  industrial  agent.  This  affinity  is,  how- 
ever, regulated,  or  rather  called  forth,  by  a  most  singular  action  of  light. 
Thus,  when  chlorine  and  hydrogen,  in  the  gaseous  condition,  are  mixed  to- 
gether in  equal  volumes,  they  will  remain  for  an  indefinite  period  without 
action  upon  each  other,  if  kept  in  the  dark.  If  the  mixture  be  exposed  to 
diffused  daylight,  combination  will  take  place  gradually ;  but  if  the  two  gases 


QUESTIONS. — What  experiments  illustrate  its  action  in  this  respect  ?  Why  does  phos- 
phorus burn  in  chlorine  with  a  feeble  light  ?  What  are  the  relations  of  chlorine  to  hy- 
drogen ?  What  influence  does  light  exert  upon  a  mixture  of  these  two  elements  ? 


CHLORINE.  239 

are  brought  into  direct  sunlight,  the  union  takes  place  instantly,  accompanied 
with  a  powerful  explosion.* 

The  following  experiment  is  illustrative :  Select  a  clear  glass  bottle  (holding 
about  a  pint),  and  fill  it  over  a  pneumatic  trough,  to  the  extent  of  half  its 
capacity,  with  chlorine  gas ;  then  carefully  cover  the  bottle  with  a  dark  cloth, 
and  add  hydrogen  from  a  gasometer  sufficient  to  occupy  the  remaining  space, 
or  until  all  the  water  in  the  bottle  is  displaced ;  cork  the  bottle,  keeping  its 
mouth  under  water,  and  remove  it  from  the  trough  carefully  and  entirely  en- 
veloped in  the  cloth.  Then  place  the  bottle  in  the  direct  light  of  the  sun,  and 
from  a  distance  remove  the  cloth  by  means  of  a  string  or  a  long  pole.  If  the 
preliminary  conditions  have  been  strictly  complied  with,  the  instant  the  rays 
of  light  fall  upon  the  mixture  a  violent  explosion  will  occur. 

"When  chlorine  in  a  free  state,  or  in  feeble  combination  with  some  other 
substance,  is  brought  in  contact  with  a  body  which  contains  hydrogen  as  one 
of  its  constituent  elements,  it  manifests  the  same  affinity  for  this  element ;  and 
tends  to  "  draw  out,"  as  it  were,  the  hydrogen  from  its  combination,  and  by 
uniting  with  it,  to  change  or  destroy  the  original  compound.  In  this  instance, 
also,  light  exercises  a  controlling  influence. 

For  example :  If  a  solution  of  chlorine  in  water  (§  351)  be  kept  in  the 
dark,  no  change  takes  place  in  it ;  but  when  exposed  to  the  action  of  sun- 
light, it  decomposes  readily.  This  result  is  produced  by  the  following  reac- 
tion : — the  chlorine  contained  in  the  solution,  by  reason  of  its  intense  affinity 
for  hydrogen,  withdraws  this  element  from  its  combination  with  oxygen  in 
the  water,  and  uniting  with  it,  forms  an  acid ;  the  oxygen  of  the  decomposed 
water,  being  no  longer  held  in  combination,  escapes  as  a  gas.  . 

354.  Theory  of  Bleach  in  g. — It  is  this  action  of  cmorine  upon  hy- 
drogen which  renders  chlorine  the  most  powerful  of  ah1  known  bleaching  and 
deodorizing  agents.  Nearly  ah1  animal  and  vegetable  coloring  matters  contain 
hydrogen  as  one  of  their  essential  constituents.  When  brought  in  contact 
with  chlorine,  the  hydrogen  they  contain  unites  with  it,  and  the  original  ar- 
rangement of  particles,  upon  which  the  color  of  the  body  depended,  being 
thus  changed  or  broken  up,  the  color  itself  is  destroyed.  Ozone,  which  is  also 
a  powerful  bleaching  agent,  acts  in  a  similar  manner ;  the  oxygen  of  which 
it  consists,  by  reason  of  its  highly  active  condition,  withdraws  hydrogen  from 
its  combination,  unites  with  it  to  form  water,  and  thus  destroys  the  arrange- 
ment upon  which  the  color  depends.  By  withdrawing  a  single  pillar  of  sup- 


*  It  has  also  been  shown  by  Dr.  Draper,  that  pure  and  dry  chlorine  gas,  when  exposed 
for  a  time  to  the  action  of  the  sun's  light,  acquires  and  retains,  for  a  considerable  period, 
the  power  of  forming  an  explosive  union  with  hydrogen,  even  in  the  dark  ;  while,  on  the 
other  hand,  chlorine  prepared  in  the  dark  manifests  no  affinity  for  hydrogen  until  exposed 
to  the  light.  This  peculiar  action  of  light  is  entirely  confined  to  the  chemical  element  of 
the  solar  ray. 

QUESTIONS — What  experiment  illustrates  this  ?  What  are  the  relations  which  chlorine 
sustains  to  hydrogen  in  combination  ?  Illustrate  by  example.  What  is  the  theory  of  bleach- 
ing by  chlorine  ?  By  ozone  ?  What  is  said  of  the  permanency  of  the  bleaching  effect  of 
of  these  agents  ? 


240  INORGANIC     CHEMISTEY. 

port,  the  whole  structure  falls.  Colors  once  removed  by  the  action  of  chlorine 
or  ozone  can  never  be  restored;  and  in  this  respect  these  two  substances  dif- 
fer from  most  other  bleaching  agents. 

The  bleaching  action  of  chlorine  may  be  illustrated  by  a  variety  of  experi- 
ments. For  this  purpose  a  solution  of  chlorine  in  water  may  be  most  con- 
veniently used.  If  we  pour  a  little  of  this  solution  upon  red  ink,  red  wine, 
the  blue  tincture  of  red  cabbage,  of  litmus,  on  indigo  solution,  or  on  ordinary 
writing  ink,  their  several  colors  almost  immediately  disappear.  Paper,  col- 
ored rags,  and  all  varieties  of  cotton  or  linen  fabrics  immersed  in  a  solution  of 
chlorine,  are  bleached  with  great  rapidity.  The  moist  gas  produces  the  same 
effect,  but  perfectly  dry  chlorine  will  not  bleach.  Fibres  of  wool  are  not 
bleached  by  the  action  of  chlorine,  neither  is  it  usually  employed  for  the 
bleaching  of  silk.  It  has  no  action  upon  "India,"  or  printers'  inks,  for  the 
reason  that  the  coloring  matter  in  these  cases  consists  of  minutely-divided 
carbon,  which  does  not  combine  directly  with  chlorine.*  By  contact  with 
chlorine  for  any  considerable  length  of  time,  the  texture  of  almost  all  organic 
substances  is  weakened  and  destroyed.  This  may  be  especially  noticed  in 
cases  where  cotton  or  linen  fabrics  have  been  wet  with  a  chlorine  solution, 
and  then  allowed  to  dry,  without  previous  thorough  washing. 

355.  Disinfecting  and  Deodorizing  Action  of  Chlorine, 
— Chlorine  acts  upon  noxious  and  odorous  vapors  and  organic  compounds  to 
decompose  and  destroy  them,  in  the  same  way  as  it  does  upon  coloring  agents. 
It  differs  essentially  in  its  action  from  many  substances  used  in  fumigation, 
such  as  burnt  paper,  vinegar,  pastiles,  perfumes,  and  the  like,  inasmuch  as, 
while  the  latter  only  disguise  the  ill  odors,  or  mephitic  atmosphere,  by  substi- 
tuting one  smell  for  another,  the  chlorine  absolutely  destroys  the  noxious 
matter  itself. 

The  use  of  chlorine  as  a  disinfectant,  however,  requires  care.  It  should  be 
used  in  the  form  of  bleaching-powder  (';  chloride  of  h'me"),  mixed  with  water, 
and  exposed  to  the  air,  hi  shallow  vessels,  if  possible  upon  a  high  shelf.  This 
compound  is  gradually  decomposed  by  the  carbonic  acid  of  the  atmosphere, 
and  the  chlorine  being  evolved  falls  slowly  down,  and  is  diffused  through  the 


*  A  very  elegant  application  of  chlorine  to  bleaching  purposes  is  made  in  the  printing 
of  bandanna  handkerchiefs.  The  white  spots,  which  constitute  their  peculiarity,  are 
thus  produced ;  First  of  all,  the  whole  fabric  is  dyed  of  one  uniform  tint,  and  dried. 
Afterward  many  layers  of  these  handkerchiefs  are  pressed  together  between  lead  plates, 
perforated  with  holes  conformable  to  the  pattern  which  is  desired  to  appear.  Chlorine 
solution  is  now  poured  upon  the  upper  plate,  and  finds  access  to  the  interior  through  the 
perforations.  By  reason  of  the  great  pressure  upon  the  mass,  the  solution  can  not,  how- 
ever, extend  laterally  further  than  the  limits  of  the  apertures,  whence  it  follows  that  the 
bleaching  agent  is  localized  to  the  desired  extent,  and  figures  corresponding  in  shape  and 
size  to  the  perforations  are  bleached  white  upon  a  dark  ground. — FAEADAY. 

QUESTIONS. — How  may  the  bleaching  action  of  chlorine  be  illustrated  ?  "What  are  ex- 
ceptions to  its  action?  What  effect  does  continued  contact  with  chlorine  have  upon 
organic  substances?  What  is  the  disinfecting  and  deodorizing  action  of  chlorine  ?  How 
does  chlorine  differ  in  its  action  from  many  fumigating  agents  ?  How  should  chlorine  be 
applied  for  disinfection  and  deodorizing  ? 


CHLORINE.  241 

room.  If  a  more  rapid  action  is  required,  a  little  dilute  sulphuric  or  hydro- 
chloric acid  may  be  allowed  to  drop  into  the  chloride  of  lime  solution  from  a 
vessel  suspended  above  it,  by  means  of  a  piece  of  lamp-wick  arranged  in  tho 
form  of  a  syphon.  Another  method  is  to  suspend  in  the  apartment,  cloths 
steeped  in  a  solution  of  bleacbing-powder ;  and  in  the  absence  of  bleaching- 
powder,  the  gas  may  be  easily  generated  by  one  of  the  methods  already  de- 
described — care  being  taken  to  avoid  excess.* 

356.  Compounds  of  Chlorin  e( — Chlorine  combines  with  all  tho 
non-metallic  elements,  with  perhaps  a  single  exception.  "With  many  of  them, 
however,  it  can  not  be  made  to  unite  directly.  It  enters  into  combination 
with  all  the  metals ;  and  with  a  large  number  of  them  directly,  with  an  evo- 
lution of  light  and  heat  The  binary  compounds  of  chlorine  are  termed 
chlorides.  "With  the  exception  of  the  chlorides  of  silver  and  load,  and  the  sub- 
chlorides  of  copper  and  mercury,  they  are  all  more  or  less  soluble  in  water, 
and  in  then-  taste  and  general  physical  character,  resemble  common  salt 

It  frequently  happens  that  chlorine  combines  with  the  same  metal  in  more* 
proportions  than  one :  for  example,  with  iron,  a  protochloride  (Fe  Cl)  and  a 
sesquichlorido  (Fe2Cls)  may  be  formed;  and  with  platinum  a  protochlorido 
(Pt  Cl)  and  a  bichloride  (Pt  Clo);  and,  generally,  for  each  oxyd  of  the  metal 
that  is  capable  of  uniting  with  acids  to  form  salts,  a  corresponding  chloride 
exists. 

Most  of  the  chlorides  of  the  metals  are  solid ;  but  some  few  are  liquid  at 
ordinary  temperatures ;  and  one,  the  porchloride  of  manganese  (Mm  Cli)  is 
gaseous.  All  of  them  are  fusible  at  a  moderate  temperature,  and  many 
are  readily  volatilized  in  the  operation ;  especially  is  this  true  of  the  chlor- 
ides of  gold,  copper,  aluminum,  magnesium,  and  several  others.  Geol- 
ogists have  taken  advantage  of  this  fact,  in  SQme  instances,  to  explain  the 
formation  of  mineral,  or  metallic  veins  in  the  rocky  strata  composing  the  crust 


*  "  It  must  be  particularly  borne  in  mind,  that  chlorine  in  any  form  must  only  be  used 
as  an  aid  to  proper  ventilation.  It  is  a  necessary  condition  of  health  that  our  houses  and 
rooms  be  properly  ventilated.  There  is  no  substitute  for  ventilation  any  more  than  for 
washing  or  for  general  cleanliness.  Chlorine,  like  medicine,  ought  in  general  to  be  used 
on  special  occasions,  and  under  advice.  In  a  sick-room,  where  ventilation  is  often  diffi- 
cult, chlorine,  liberated  in  very  minute  quantities,  will  often  be  found  singularly  refresh- 
ing ;  but  in  this,  as  in  all  other  cases  of  fumigation  with  chlorine,  all  metallic  articles  in 
the  apartment  ought  to  be  removed,  for  these  become  speedily  tarnished  by  the  action  of 
chlorine. 

"  For  disinfecting  the  wards  of  hospitals  and  similar  places,  Prof.  Faraday  found  that 
a  mixture  of  1  part  of  common  salt,  and  1  part  of  the  binoxyd  of  manganese,  when  acted 
upon  by  2  parts  of  oil  of  vitriol  previously  mixed  with  1  part  of  water  (all  by  weight),  and 
left  till  cold,  produced  the  best  results.  Such  a  mixture  at  60°  F.,  in  shallow  pans  of 
earthen  ware,  liberated  its  chlorine  gradually  but  perfectly  in  four  days.  The  salt  and 
the  manganese  were  well  mixed  and  used  in  charges  of  3|  pounds  of  the  mixture.  The 
acid  and  water  were  mixed  in  a  wooden  tub,  the  water  being  put  in  first,  and  then  about 
half  the  acid  ;  after  cooling  the  other  half  was  added.  The  proportions  of  water  and  acid 
are  9  measures  of  the  former  to  10  of  the  latter." 

QUESTIONS. — What  is  said  of  the  compounds  of  chlorine  ?  What  are  the  compounds 
of  chlorine  termed  ?  What  are  the  general  properties  of  the  chlorides  ? 

11 


242  INOEGANIC     CHEMISTRY. 

of  our  globo.  It  is  supposed  that  the  metals,  in  the  form  of  chlorides,  have 
been  sublimed  or  volatJkel  by  intense  heat  from  the  interior  of  the  earth,  and 
ris'ng  through  openings  and  fissures  in  the  rocks,  have  been  deposited,  as  they 
cooled,  in  the  situations  in  which  they  are  now  found. 

Formerly,  before  the  constitution  of  chlorine  was  fully  understood^  its  com- 
pounds with  the  metals  were  termed  muriates.  The  names,  muriate  of  tin, 
muriate  of  soda,  muriate  of  iron,  have  therefore  the  same  signification  as 
chloride  of  tin,  chloride  of  soda,  chloride  of  iron,  etc. 

357.  Hydrochloric    Acid,    II C i  1.  —  Chloroliydric    Acid  ; 
Chloride  of  Hydrogen;  Muriatic  Acid. — This  substance, 
formed  by  the  union  of  chlorine  and  hydrogen,  is  the  most 
important  of  all  the  compounds  which  chlorine  forms  with, 
the  non-metallic  elements. 

It  was  first  obtained  by  Priestley  in  its  pure  form  of  a  gas,  in  1772  ;  and  in 
a  state  of  solution  in  water,  it  has  long  been  known  under  the  names  of  muri- 
atic acid,  and  spirit  of  salt.  In  the  latter  condition  it  constitutes  a  strong, 
corrosive  acid  liquid. 

358.  Preparatio  n, — "VYhen  chlorine  and  hydrogen  are  mixed  together 
$n  the  proportion  of  equal  volumes,  and  a  chemical   combination  is  effected 
between  them,  they  unite,  without  condensation,  to  form  hydrochloric  acid 
gas.     This  union  may  be  brought  about  by  the  action  of  light,  in  the  manner 
before  described  (§  353),  by  the  application  of  an  ignited  match,  or  by  the 
passage  of  the  electric  spark — the  combination  in  the  lattewmstances  being 
always  attended  with  an  explosion. 

•p,  Q    -Qtj  For  experimental  purposes,  hydrochloric 

acid  gas  may  be  procured  by  heating  in  a 
glass  flask,  furnished  with  a  perforated  cork 
and  tube,  a  quantity  of  strong  commercial 
muriatic  acid.  The  gas  is  readily  given  off 
by  the  application  of  a  gentle  heat,  and  may 
be  collected  by  displacement  of  air  in  dry 
vessels.  (See  Fig.  117.) 

For  most  practical  purposes,  hydrochloric 
acid  is  obtained  by  action  of  sulphuric  acid 
upon  common  salt.  "When  the  process  is 
conducted  on  a  small  scale,  and  hi  a  glass  retort,  or  an  apparatus  similar  to 
that  represented  in  Fig.  117,  3  parts  of  common  salt,  5  of  strong  sulph 
acid,  and  5  of  water  may  be  taken.  The  reaction  in  this  case  is  as  follow 
common  salt  is  composed  of  chlorine  and  sodium  ;  when  mixed  with  sulphx 
acid  and  water,  the  water  is  decomposed ;  its  hydrogen  uniting  with 
chlorine  of  the  common  salt  to  form  hydrochloric  acid,  and  its  oxygen 

QUESTIONS. — What  theory  has  been  proposed  to  account  for  the  origin  of  mineral  veir 
What  are  muriates  ?    What  is  hydrochloric  acid  ?    How  may  it  be  prepared  ?    How  is  i 
prepared  for  practical  purposes? 


CHLORINE.  243 

the  sodium  to  form  soda,  which  last  unites  with  the  sulphuric  acid  to  form 
sulphate  of  soda.     Expressed  in  symbols,  we  have — 

Common  salt.    Sulph.  acid.        Water.          Sulphate  of  soda.    Hydrochloric  acid. 

NaCl    +    S03    +    HO  —  NaO,S03     +    HC1 

359.  Properties  . — Hydrochloric  acid  is  a  colorless  acid  gas,  of  a  pe- 
culiar pungent  odor,  producing  white  fumes  when  allowed  to  escape,  by 
uniting  with  and  condensing  the  moisture  of  the  atmosphere.  It  is  quite  un- 
respirable,  but  is  much  less  nauseous  and  suffocating  than  chlorine.  It  pro- 
duces coughing  when  breathed  in  even  the  most  dilute  condition.  It  is  heavier 
than  air,  and  has  a  specific  gravity  of  1*24.  Under  a  pressure  of  40  atmos- 
pheres at  50°  F.,  it  condenses  to  a  colorless  liquid,  which  has  never  been 
frozen.  It  is  incombustible,  extinguishes  burning  bodies  and  when  brought 
in  contact  with  dry  and  blue  litmus  paper  reddens  it. 

Hydrochloric  acid  gas  is  especially  characterized  by  a  most  intense  attrac- 
tion for  water,  which  liquid  at  a  temperature  of  40°  F.  is  capable  of  absorbing 
about  480  times  its  bulk  of  gas — increasing  in  volume  thereby  about  one 
third,  and  acquiring  a  specific  gravity  of  1'21.  "Water  of  a  higher  temperature 
absorbs  less.  A  piece  of  ice  passed  into  a  jar  of  hydrochloric  acid  gas  stand- 
ing over  mercury  is  instantly  liquefied  by  it ;  and  the  gas  at  the  same  mo- 
ment disappearing  by  absorption,  the  mercury  rises  to  fill  the  jar.  By  reason 
of  its  great  solubility  in  water,  it  can  only  be  collected  over  mercury,  or  by 
the  displacement  of  air. 

360.  Solution  of  Hydrochloric  Acid,  which  constitutes 
the  liquid  acid,  or  the  muriatic  acid  of  commerce,  is  pre- 
pared by  generating  the  gas  from  a  mixture  of  salt  and 
dilute  sulphuric  acid,  and  allowing  it  to  pass  through  and 
become  absorbed  by  water. 

The  gas  is  conducted  from  the  retort  or  generating  vessel  into  a  series  of 
bottles  or  jars  connected  with  each  other  and  filled  with  water.  When  the 
water  in  the  first  vessel  becomes  saturated  with  hydrochloric  acid,  the  gas 
passes  over  into  the  second,  thence  into  the  third,  and  so  on,  saturating  each 
successively.  Several  contingencies,  however,  mast  be  provided  for  in  this 
operation ;  the  evolution  of  gas  may  take  place  so  rapidly  as  to  rupture  the 
receivers,  or  the  gas  delivered  slowly  may  be  absorbed  so  completely  by  the 
water  as  to  produce  a  vacuum ;  in  which  case  the  whole  liquid  contents  of 
the  receivers  flow  back  violently  into  the  retort,  and  thus  put  an  end  to  the 
process. 


QUESTIONS. — Explain  the  chemical  reaction  in  this  case  ?  What  are  the  properties  of 
hydrochloric  acid  gas  ?  What  is  said  of  its  attraction  for  water  ?  What  is  the  mnriatic 
acid  of  commerce  ?  How  is  it  prepared  ?  What  precautions  are  to  be  observed  in  its  pre- 
paration ? 


244 


INORGANIC    CHEMISTRY. 


Woulfe's  Apparat  u  s.— -To  obviate  these  difficulties,  a  series  of 
peculiar- shaped  vessels,  known  as  "  "Woulfe's  bottles,"  are  employed.  These 
consist  of  glass  jars,  or  bottles,  provided  with  three  necks,  or  apertures,  (see 
Fig.  118),  each  of  which  is  fitted  with  a  perforated  cork  and  tube.  The  man- 
ner in  which  the  gas  enters  and  is  discharged  from  the  vessel  will  be  readily 
understood  by  an  inspection  of  the  figure.  The  middle  aperture  is  fitted  with 
a  single  upright  tube,  called  the  "  safety  tube,"  which  dips  beneath  the  sur- 
lace  of  the  liquid  contained  in  the  vessel.  If  the  pressure  of  gas  becomes 

FIG.  118. 


excessive,  the  water  is  forced  up  the  center  tube,  and  the  pressure  is  relieved. 
If  a  vacuum  is  created,  air  enters  from  without  to  fill  it.  By  the  condensa- 
tion of  the  hydrochloric  acid  gas,  much  latent  heat  is  liberated,  and  the  water 
which  absorbs  it  soon  becomes  elevated  in  temperature  ;  to  obtain,  therefore, 
the  most  concentrated  solution  of  gas,  it  is  necessary  that  the  receivers  should 
be  immersed  in  cold  water,  or  surrounded  with  ice.  Connection  between  the 
separate  Woulfe's  bottles  is  effected  by  means  of  a  flexible  tube  of  India- 
rubber. 

Hydrochloric  acid  solution,  when  pure,  is  a  colorless  liquid,  fuming,  when 
concentrated,  on  exposure  to  air.  The  commercial  "  muriatic"  acid  is  gener- 
ally of  yellow,  or  straw  color,  owing  to  the  presence  of  iron  and  other  impu- 
rities. It  constitutes  one  of  the  three  great  acids  of  commerce,  and  is  exten- 
sively used  as  a  reagent  in  chemical  operations,  and  to  some  extent  in  medi- 
cine as  a  tonic.  In  the  manufacture  of  "  soda  ash"  (carbonate  of  soda),  by 
the  decomposition  of  common  salt,  hydrochloric  acid  gas  is  prepared  as  an 
incidental  product  in  immense  quantities ;  and  in  some  of  the  great  manu- 
facturing establishments  of  Great  Britain  it  is  regarded  as  a  waste  product, 
the  disposal  of  which  is  attended  with  difficulty  and  expense.* 


*  It,  was  usual  to  allow  the  acid  gas  to  escape  into  the  air  by  means  of  a  chimney,  on 
emerging  from  the  top  of  which  it  formed,  in  contact  with  moisture,  white  clouds  of  acid, 


QUESTIONS.— Describe  the  construction  and  use  of  Woulfe's  bottles.  What  are  the 
physical  properties  of  hydrochloric  acid  solution?  What  are  its  uses?  Of  what  branch 
of  manufacture  is  it  an  incidental  product  ? 


CHLORINE.  245 

Free  hydrocliloric  acid,  derived  from  the  salt  contained  in  food,  is  found  in 
the  stomach,  as  a  constituent  of  the  gastric  juice.  Its  presence,  and  that  of 
the  soluble  chlorides  in  solution,  is  indicated  by  the  formation  of  a  white, 
curdy  precipitate,  when  nitrate  of  silver  in  solution  is  added  to  the  liquid. 
This  precipitate — chloride  of  silver — is  soluble  in  ammonia,  but  insoluble  in 
nitric  acid.  t  *.*/£) 

361.  Aqua  Regia,—  Nitro-Muriutic  Acid. — The  name  of 
aqua  regia  (royal  water)  was  given  by  the  alchemists  to  a 
mixture  of  nitric  with  hydrochloric  acid,  from  the  power 
that  it  possesses  of  dissolving  gold,  the   "  king  of  the 
metals/' 

Gold  and  platinum  are  insoluble  in  either  acid  separately ;  but  when  the 
two  acids  are  mixed,  they  mutually  decompose  each  other  in  the  presence  of 
the  metals — free  chlorine,  and  a  compound  of  chlorine  and  an  oxyd  of  nitrogen 
being  liberated.  The  chlorine,  in  the  moment  of  its  extrication,  or  in  its 
nascent  state  (page  162),  acts  upon  the  metals  and  dissolves  them — the  pro- 
ducts formed  being  chlorides. 

The  best  proportions  of  aqua  regia  are  one  of  nitric  acid  by  measure  to  two 
hydrochloric. 

362.  Oxyds    of   Chlorine . — Although  chlorine  and  oxygen  will  not, 
Tinder  any  circumstances,  unite  directly,  several  compounds  of  these  elements 
may  be  obtained  by  indirect  methods.     The  composition  and  names  of  the 
most  important  are  indicated  in  the  following  table : — 

Composition  by  weight. 

Symbol.  , • , 

Hypochlorous  acid (J1O  35 '5  chlorine.    8  oxygen. 

Chlorous  acid C1O3  35'5        "        24      " 

Peroxyd  of  chlorine C1O4  35'5        "        32      " 

Chloric  acid ClOs  35-5       "        40      " 

Hyperchloric  acid C1O7  35-5        "         66      " 

363.  Hypochlorous   Acid . — This  compound  may  be  produced  by 
the  action  of  chlorine  upon  red  oxyd  of  mercury.     It  is  a  yellow  gas,  readily 


•which,  wafted  by  the  wind,  produce  a  corrosive  rain,  most  ruinous  to  the  vegetation  of 
the  surrounding  country.  Many  soda  works  in  Great  Britain  were,  therefore,  indicted  as 
nuisances  on  this  account,  and  attempts  were  made  to  remedy  the  evil  by  discharging  the 
fumes  at  great  elevations,  where  it  was  supposed  they  would  become  so  diluted  by  admix- 
ture with  vapor  as  to  be  rendered  harmless.  To  carry  out  this  scheme,  the  most  gigantic 
chimneys  ever  built  were  constructed.  One  near  Liverpool  is  495  feet  high,  30  feet  in 
diameter  at  the  base,  11  feet  at  the  top,  and  contains  a  million  of  bricks.  Another  at 
Glasgow  is  still  larger.  These  costly  structures  have  not,  however,  been  found  to  answer 
the  purpose  for  which  they  were  intended,  and  it  has  become  necessary  to  condense  the 
gas  as  fast  as  it  is  liberated  by  bringing  it  into  contact  with  cold  water.  But  even  this, 
taken  in  connection  with  the  disposal  of  the  great  quantity  of  liquid  acid  formed,  is  a 
matter  of  great  difficulty,  and  many  arrangements  have  been  patented  to  effect  it. 

QUESTIONS. — Does  it  exist  in  the  animal  economy  ?  What  is  a  test  of  its  presence  ? 
What  is  aqua  regia  ?  Why  so  called?  How  is  it  enabled  to  dissolve  gold  ?  What  is  said 
of  the  oxyds  of  chlorine  ?  What  is  hypochlorous  acid  ? 


246  INORGANIC     CHEMISTRY. 

absorbed  by  water,  and  condensed  by  the  application  of  cold  into  an  orange- 
yellow  liquid. 

3G4.  Bleaching  Compounds . — When  chlorine  gas  is  caused  to 
pass  through  weak  solutions  of  the  alkalies,  or  over  hydrate  of  lime  (slacked 
lime),  it  is  absorbed,  and  very  peculiar  compounds,  possessed  of  remarkable 
bleaching  properties,  are  produced.  It  is  in  this  way  that  the  bleaching 
agents  so  extensively  used  in  the  arts  under  the  names  of  chloride  of  lime 
(bleaching  powder)  chloride  of  soda,  and  chloride  of  potash,  together  with 
What  are  called  "  disinfecting  fluids,"  are  prepared. 

These  compounds,  according  to  the  opinion  of  most  chemists,  are  formed 
by  the  union  of  hypochlorous  acid  with  an  oxyd  of  a  metal,  and  are  termed 
liypochlorites.  Thus  the  constitution  of  the  so-called  chloride  of  lime  would 
be  represented  in  symbols  as  follows :  CaO,  CIO.  Other  authorities  deny  the 
formation  of  hypochlorous  acid,  and  regard  the  compounds  in  question  as 
formed  by  the  direct  union  of  chlorine  with  an  oxyd.  According  to  this  latter 
view,  the  constitution  of  chloride  of  lime,  represented  in  symbols,  would  be  as 
follows:  CaO,  01. 

365.  Chloride  of  Lime,  or  Bkaehing-Powder,  is  the  most  important 
of  ah1  the  bleaching  compounds  of  chlorine,  and  is  used  in  immense  quantities 
for  the  bleaching  of  paper,  cotton,  and  linen  fabrics,  and  for  disinfecting  pur- 
poses. Its  manufacture  is  almost  a  monopoly  with  Great  Britain,  and  no  at- 
tempt to  prepare  it  on  a  large  scale  in  this  country  has  ever  proved  success- 
ful.* The  process  consists  essentially  in  exposing  fresh  slacked  lime,  spread 
out  upon  shelves  in  large  leaden  or  stone  chambers,  to  the  action  of  gaseous 
chlorine — the  operation  being  continued  until  the  lime  has  absorbed,  or  united 
with  the  largest  possible  amount  of  the  gas.  It  is  then  withdrawn,  and  made 
ready  for  transportation  by  enclosure  in  tight  casks.  As  thus  prepared,  it  is 
a  soft  white  powder,  partially  soluble  in  water,  and  possessing  a  chlorine-like 
odor.  "When  exposed  to  the  air  it  is  readily  decomposed,  carbonic  acid  being 
absorbed,  and  chlorine  liberated. 

Ordinary  bleaching-powders  contain  about  30  per  cent,  of  available  chlo- 
rine. The  testing  of  their  commercial  value  is  termed  chtorimetry,  and  the 
method  adopted  generally  consists  in  ascertaining  by  experiment  how  many 
grams  of  a  particular  sample  are  required  to  destroy  the  color  of  a  known 
weight  of  indigo  hi  solution.  The  result,  compared  with  the  results  of  certain 
standard  experiments,  give  the  percentage. 


*  The  reason  why  the  manufacture  of  bleaching-powder  has  not  been  introduced  into 
the  United  States,  is  due  doubtless  to  the  fact,  that  it  can  only  be  economically  conducted 
in  connection  with  the  manufacture  of  soda-ash,  which  process  furnishes  hydroclil  ric 
acid,  from  whence  chlorine  is  procured,  at  a  mere  nominal  cost ;  and  to  carry  on  both 
operations  advantageously  requires  the  employment  of  great  capital  and  skill. 


QUESTIONS. — How  are  the  ordinary  bleaching  compounds  and  "disinfecting  fluids" 
formed  ?  What  is  said  of  the  composition  of  these  compounds  ?  What  is  said  of  chloride 
of  lime  ?  How  is  it  prepared  ?  What  is  chlorimetry  ?  How  is  it  conducted  ? 


CHLORINE.  247 

"What  is  called  "  Labarraque's  disinfecting  liquid,"  is  a  solution  of  a  com- 
pound of  chlorine  and  soda.,  similar  in  composition  to  bleaching-powder. 
"Burnet's  disinfecting  fluid"  is  a  compound  of  chlorine  and  zinc. 

366.  C  h  1  o  r  i  c    Acid,  C105. — This  compound  is  not  known  in  an  iso- 
lated state,  and  is  never  obtained  except  in  combination  with  water  (CIO5 
110).     When  a  stream  of  chlorine  gas  is  transmitted  through  a  strong  solu- 
tion of  caustic  potash,  the  gas  is  absorbed,  and  a  bleaching  solution,  as  before 
described,  is  formed.     This,  by  standing,  or  by  the  application  of  heat,  loses 
its  bleaching  property,  and  becomes  a  mixture  of  chloride  of  potassium  and 
chlorate  of  potash ;  the  latter  of  which,  being  the  least  soluble,  separates  on 
concentrating  the  liquid,  into  shining  tabular 'crystals.    In  this  reaction,  a  part 
of  the  potash  is  decomposed ;  its  oxygen  combining  with  one  portion  of  chlor- 
ine to  form  chloric  acid,  while  the  potassium  is  taken  up  by  a  second  portion 
of  the  same  substance;  or  in  symbols: — 

6  01+ 6  KO=KO,Cl5+5  KCL 

Chlorates  of  other  bases  are  formed  in  a  similar  manner. 

367.  Propertie  s. — All  of  tho  chlorates,  when  exposed  to  moderate 
heat,  undergo  decomposition,  and  liberate  oxygen  most  abundantly ;  they 
are,  therefore,  generally  used  for  the  production  of  oxygen  (§  281).     "When 
thrown  upon  ignited  charcoal,  the  chlorates  deflagrate  with  scintillations,  and 
when  heated  with  substances  which  have  a  strong  attraction  for  oxygen,  such 
as  phosphorus  and  sulphur,  they  explode  violently  (§  285).     Mere  friction, 
also,  with  these  elements  is  sufficient  to  cause  a  detonation ;  for  example,  if  a 
half  a  gram  of  sulphur  be  triturated  in  a  mortar  with  two  or  three  grams  of 
chlorate  of  potash,  the  friction  is  attended  with  a  series  of  small  explosions. 
A  mixture  of  chlorate  of  potash,  sulphur,  and  a  little  charcoal,  was  formerly 
used  as  a  percussion  powder  for  gun-caps  j  but  its  action  upon  the  locks  was 
found  to  be  highly  corrosive. 

Paper  soaked  in  a  solution  of  a  chlorate,  burns  in  tho  same  manner  as  touch- 
paper. 

An  attempt  was  made  by  the  French  government,  toward  the  close  of  tho 
last  century,  to  substitute  chlorate  of  potash  in  place  of  niter  (saltpeter)  in  the 
manufacture  of  gunpowder ;  but  the  liability  to  accidental  explosion  was  so 
greatly  increased,  that  the  enterprise  was  speedily  abandoned.  It  is,  how- 
ever, still  used  to  a  very  great  extent  in  the  manufacture  of  fire-works,  and 
especially  in  the  production  of  colored  fires. 

3C8.  Peroxyd  of  Chlorine,  C104.  Hypochloric  Acid. — This  sub- 
stance, which  can  not  bo  obtained  in  a  state  of  purity  without  great  danger, 
is  prepared  by  distilling  chlorate  of  potash  with  strong  sulphuric  acid.  It  is  a 
gas  of  a  yellow  color,  which  is  gradually  decomposed  by  the  influence  of  light, 
and  at  a  temperature  less  than  that  of  boiling  water,  its  elements  separate 


QUESTIONS. — What  are  Labarraque's  and  Burnet's  disinfecting  fluids  ?  What  is  said  of 
chloric  acid  ?  How  is  chlorate  of  potash  prepared  ?  What  are  the  properties  of  the 
chlorates  ?  For  what  purposes  are  they  practically  employed  ?  What  is  said  of  peroxyd 
of  chlorine  ? 


248  INORGANIC    CHEMISTRY. 

with  a  most  violent  explosion.     Mere  contact  with  many  combustible  matters 
also  occasion  an  immediate  explosion. 

Some  of  the  properties  of  this  singular  compound  may  be  experimentally 
illustrated  without  danger.  If  a  few  grains  of  loaf  sugar  and  chlorate  of  pot- 
ash be  separately  pulverized,  and  mixed  together  in  equal  proportions,  with- 
out friction,  the  addition  of  a  single  drop  of  sulphuric  acid,  let  fall  from  the? 
end  of  a  glass  rodr  will  produce  instantaneous  and  brilliant  deflagration.  The 
chemical  reaction  which  occasions  this  result  is  as  follows :  The  sulphuric 
acid  decomposes  the  chlorate  of  potash,  and  liberates  peroxyd  of  chlorine ; 
this,  in  turn,  by  contact  with  the  sugarr  is  decomposed,  and  evolves  heat  suf- 
ficient to  produce  combustion. 

Another  very  brilliant  experiment  consists  in  bringing  phosphorus  in  contact 
with  peroxyd  of  chlorine  under  water  at  the  very  instant  ot  its  development. 
A  deep  glass  vessel  being-  chosen  (a  conical  wine-glass  will  answer),  a  few 
small  pieces  of  phosphorus  are  first  thrown  in,  and  the  glass  two  thirds  filled 
with  water.  Crystals  of  chlorate  of  potash,  about  equal  in  quantity  to  the 
phosphorus  employed,  are  then  allowed  to  fall  through  the  water  and  settle 
upon  the  phosphorus.  All  that  now  remain  to  be 
done  is  to  bring  sulphuric  acid  in  contact  with  the  two, 
which  is  easily  accomplished  by  means  oi  a  dropping- 
tube,  or  small  glass  tube  and  funnel — the  extremity 
ot  either  of  which  being  brought  in  contact  with  the 
mixture,  the  sulphuric  acid  is  caused  to  touch  the 
solids,  without  mixing-  with,  and  suffering  dilution  by, 
the  water,  (See  Fig,  119.)  Peroxyd  of  chlorine  being- 
rapidly  evolved,  the  phosphorus  reacts  upon  it,  and 
flashes  ot  a  beautiful  green  light  under  water,  attended 
•with  a  crackling  noise,  are  produced. 

The  two  other  principal  compounds  of  chlorine  with 
oxygen,  chlorous  and  perchloric  acid,  although  of  scientific  interest,  are  of  no- 
practical  importance. 

369.  Chloride  of  IVitrog-e  n. — The  single  compound  which  chlorine 
is  known  to  form  with  nitrogen,  is  especially  worthy  of  note  as  probably  the 
most  dangerous  of  all  chemical  combinations. 

When  a  bottle  of  chlorine,  perfectly  free  from  greasy  matter,  is  inverted 
over  a  leaden  dish  containing  a  solution  of  1  part  of  sal-ammoniac  (NILtCl)  in 
12  parts  of  water — the  mouth  of  the  bottle  slightly  dipping  beneath  the  sur- 
face— drops  of  an  oily-looking  substance  wifl  gradually  form  upon  the  liquid 
and  fall  to  the  bottom  of  the  dish,— chlorine  slowly  disappearing.  The  fluid 
substance  thus  generated  is  cliloride  of  nitrogen.  During  the  whole  opera- 
tion, the  bottle  must  not  be  approached,  unless  the  face  is  protected  by  a  wire- 
gauze  mask,  and  the  hands  by  thick  woollen  gloves.  The  leaden  dish  con- 
taining the  chloride  of  nitrogen,  may,  after  a  time,  however,  be  withdrawn 

QUESTIONS.—  How  may  its  properties  foe  illustrated  ?  What  is  said  of  chloride  of  nitro- 
gen ?  How  is  it  prepared  ? 


c  H  L  o  n  i  N  £  ,  249 

from  under  the  bottle,  care  being  taken  to  avoid  all  agitation  and  contact  with 
the  glass. 

As  thus  prepared,  it  is  a  volatile,  oily  liquid,  With  a  peculiar,  penetrating 
odor.  When  heated  to  about  200°  !%  or  when  merely  touched  with  a  greasy 
substance,  with  phosphorus  or  an  alkali,  or  even  when  subjected  to  the  slight- 
est friction  or  jarring,  it  explodes  with  a  flash  of  light  and  a  violence  that  is 
difficult  to  conceive  of,  Glass  and  cast-iron  in  proximity  to  it,  are  shattered 
into  fragments,  and  a  single  drop  has  been  known  to  cause  a  perforation 
through  a  thick  plank,  A  leaden  vessel  yields  to  its  effects,  and  is  merely 
indented. 

The  chemical  constitution  of  this  body  is  not  certainly  known  j  neither  are 
the  principles  involved  in  its  remarkable  reactions  at  all  understood,  Sim- 
ilar compounds  of  nitrogen  may  also  be  formed  with  iodine,  bromine,  and  cy- 
anogen, 

370,  History  of  Bleach  in  g,— The  past  history  and  present  condi- 
tion of  the  great  industrial  art  of  bleaching  appropriately  connects  itself  with 
the  subject  of  chlorine.  Before  the  Discovery  and  application  of  this  element, 
the  operation  of  bleaching  cotton  and  linen  consisted  essentially  in  washing 
and  boiling  the  fabrics  in  hot  water,  with  soap  and  alk alies,  and  subsequently 
exposing  them  for  a  lengthened  period  on  the  grass  to  the  action  of  light  and 
air.  These  operations  were  successively  repeated,  and  the  time  required  to 
render  a  piece  of  linen  white  and  suitable  for  market,  varied  from  four  to 
eight  months,  During  the  16th  and  17th  centuries,  the  Dutch  enjoyed  an 
almost  complete  monopoly  of  the  business,  and  almost  all  the  linen  goods 
manufactured  in  Europe  were  sent  to  Holland  to  be  bleached.  The  Dutch 
affixed  their  imprint  on  all  goods  bleached  by  them,  which  were  afterward 
known  as  "  Hollands,"  a  term  applied  to  linens  even  at  the  present  day. 

This  method  of  bleaching  was  extremely  expensive,  not  only  on  account  of 
the  time  and  labor  required  in  the  operation,  but  also  from  the  great  extent 
of  grass-laud  necessary  for  the  spreading  of  the  cloths.  Goods  thus  exposed 
out'-of-doors  served  as  a  temptation  to  dishonest  persons,  and  the  old  statute 
laws  of  England  abound  in  severe  penalties  against  trespassers  upon  bleach* 
fields. 

The  decolorizing  action  observed  to  take  place1  when  organic  products  are 
exposed  to  the  action  of  light,  air,  and  moisture,  is  explained  on  the  same 
general  principles,  as  in  the  case  of  chlorine  (§  354);  viz.,  the  coloring  com- 
pound is  broken  up  by  the  abstraction  or  union  of  its  hydrogen  constituent 
with  the  oxygen  of  the  air,  or  with  the  oxygen  contained  in  dew  and  aqueous 
vapors,  it  being  a  fact  that  "grass-bleaching"  is  most  rapid  at  those  seasons 
and  times  when  the  deposit  of  dew  is  most  copious  and  abundant.  It  is  also 
probable  that  the  ozone  present  in  the  atmosphere  exerts  some  effect,  and 
the  chemical  action  of  light  is  known  to  be  essential,  inasmuch  as  the  bleach- 
ing will  not  take  place  in  the  dark, 

QUESTIONS.— What  are  its  characteristic  properties?  What  was  the  original  method 
of  bleaching  ?  What  is  said  of  the  early  history  of  bleaching  ? 


250  INORGANIC     CHEMISTRY. 

One  of  the  improvements  in  bleaching  introduced  by  the  Dutch  was  that  of 
''souring,"  which  consisted  in  steeping  the  goods  for  a  considerable  length  of 
time  in  sour  milk;  but  about  the  year  1750,  very  dilute  sulphuric  acid  was 
Substituted  in  its  place.  This  simple  change  was  a  most  important  discovery, 
inasmuch  as  it  shortened  the  time  required  for  bleaching  linen  by  nearly  three 
months,  and  greatly  reduced  the  expense.  In  fact,  the  operation  of  "  souring" 
by  sulphuric  acid  still  forms  an  essential  feature  of  the  modern  processes  of 
bleaching. . 

In  1785,  Berthollet,  a  French  chemist,  while  repeating  some  experiments  on 
chlorine,  which  had  been  discovered  by  Scheele  in  1774,  ascertained  that  a 
solution  of  this  gas  in  water  was  capable  of  destroying  vegetable  colors,  and 
he  was  hence  led  to  suggest  its  application  to  bleaching.  About  this  time 
Berthollet  was  visited  by  James  Watt,  of  England,  celebrated  from  his  connec- 
tion with  the  steam-engine,  to  whom  he  related  the  results  of  his  experiments. 
"Watt,  on  his  return  to  England,  practically  examined  the  subject,  and  made 
a  successful  trial  of  bleaching  with  the  new  agent,  at  an  establishment  near 
Glasgow,  Scotland.  From  thence  its  us*  rapidly  extended  throughout  Great 
Britain. 

The  introduction  of  chlorine  as  a,  bleaching  agent,  like  all  other  great  dis- 
coveries which  tend  to  overturn  old  practices,  encountered  a  most  strenuous 
opposition. 

The  first  method  of  using  it,  consisted  in  saturating  cold  water  with 
the  gas,  and  immersing  the  goods  to  be  bleached  in  the  solution.  Heat 
being  applied,  the  chlorine  was  evolved  from  the  water  and  acted  upon  the 
coloring  matters.  The  difficulties  which  attended  this  procedure  were,  that 
the  gas  was  evolved  so  abundantly,  that  the  workmen  were  unable  to  enduro 
it,  and  the  strength  of  the  cloth  also  was  impaired.  A  defect  of  the  goods, 
becoming  yellow  after  some  days,  led  to  the  operation  of  boiling  in  alkaline 
leys,  when  it  was  discovered  that  solutions  of  the  alkalies  not  only  absorb  a 
greater  quantity  of  chlorine  than  water,  but  hold  it  with  greater  affinity — not 
allowing  the  gas  to  escape  and  affect  the  atmosphere,  but  at  the  same  time 
imparting  it  regularly  and  effectively  to  fabrics  in  contact  with  them.  The 
knowledge  of  these  facts  prepared  the  way  for  the  further  discovery,  in  1798, 
by  Mr.  Tennant,  of  Scotland,  of  the  compound  known  as  "  chloride  of  lime," 
or  "bleaching-powder,"  the  manufacture  of  which  has  been  already  described 
(§  365).*  During  all  this  period  the  constitution  of  the  bleaching  agent  in 


*  Chlorine,  in  its  combination  with  lime,  is  completely  under  the  control  of  the  manu- 
facturer, and  can  be  used  with  any  amount  of  violence,  so  to  speak,  within  the  limits  of 
its  powers.  It  may  be  developed  at  once,  if  desired,  or  its  evolution  can  be  effected  by 
the  slowest  degrees.  It  is  possible  to  so  dilute  bleaching-powder  with  water,  that  it  shall 
exercise  no  bleaching  effect  of  itself,  but  this  effect  shall  be  developed  by  the  disturbing 
action  of  a  third  substance.  This  may  be  illustrated  by  making  an  exceedingly  dilute 

QTTEBTIONB.— What  improvement  was  introduced  by  the  Dutch  ?  What  was  the  next 
advance  in  the  art?  What  did  Berthollet  discover?  What  followed  Berthollet' s  discov- 
ery? What  was  the  first  method  of  bleaching  by  chlorine  ?  What  difficulties  were  en- 
countered ?  How  were  they  overcome  ? 


CHLORINE.  251 

question  wag  unknown,  it  being  regarded  as  a  compound  containing  oxygen, 
termed  "  oxy-muriatic  acid;"  and  it  was  not  until  1811  that  Sir  Humphrey 
Davy  demonstrated  its  true  elementary  character,  and  called  it  chlorine. 

Some  idea  of  the  wonderful  results  which  have  flowed  from  the  discovery 
and  practical  application  of  chlorine  may  be  formed  from  the  following  facts : 
bleaching  operations,  which  less  than  one  hundred  years  ago,  required  from 
four  to  eight  months,  are  now  accomplished  in  comparatively  few  hours ;  the 
quantity  of  cloth  bleached  by  several  of  the  large  establishments  of  England 
and  the  United  States  ranges  from  twenty  to  fifty  thousand  yards  per  day ; 
and  it  has  been  further  estimated  that  all  the  available  labor  of  the  civilized 
world  would  at  the  present  time  be  insufficient  to  supply,  by  the  old  process, 
the  present  demand  and  consumption  of  bleached  cottons  and  linens. 

The  operations  of  a  modern  bleachery  for  cotton  fabrics  may  be  briefly  de- 
scribed as  follows: — "All  cotton  fibers  are  covered  with  a  resinous  substance, 
which,  to  a  certain  extent,  prevents  the  absorption  of  moisture,  and  also  with 
a  yellow  coloring  matter,  which,  in  some  kinds  of  cotton,  is  so  marked  as  to 
give  a  distinctive  character  to  the  fabric  made  from  it,  as  in  nankeen,  which 
is  manufactured  in  China  from  a  native  brown  cotton.  In  some  varieties  of 
cotton  the  quantity  of  coloring  mater  is  so  smah1  that  the  fabric  would  not  re- 
quire bleaching  were  it  not  for  the  impurities  acquired  in  spinning  and  weav- 
ing." 

The  first  process  of  bleaching  is  called  "singeing,"  and  consists  in  passing 
the  cloth  with  great  rapidity  over  a  red-hot  copper  cylinder.  This  burns,  or 
"  singes"  off  the  fibrous  down  or  "  nap"  from  the  surface  of  the  cloth,  render- 
ing it  smooth  and  more  suitable  for  the  reception  of  colors,  in  subsequent 
operations  of  dyeing  and  calico  printing. 

After  singeing  the  goods  are  placed  in  large  hollow  wheels,  each  of  which 
lias  four  compartments,  with  openings,  upon  its  face.  (See  Fig.  120).  Water 
being  admitted  into  the  compartments  by  means  of  a  pipe  concentric  with  the 

solution  of  chloride  of  lime  in  water ;  so  dilute  that  a  solution  of  indigo  poured  into  it  is 
not  perceptibly  decolorized.  If  we  now  add  a  third  or  disturbing  agency,  in  the  form  of 
a  few  drops  of  acid  of  any  kind,  chlorine  is  liberated,  and  decoloration  takes  place.  A 
very  beautiful  application  of  this  property  is  made  in  calico-printing.  Suppose  it  is  de- 
sired to  produce  a  white  pattern  on  a  colored  ground — white  dots  or  leaves,  for  example, 
on  a  field  of  bright  red,  the  red  being  a  color  removable  by  the  agency  of  chlorine — this  re- 
sult is  effected  by  the  following  course  of  manipulation :  The  whole  fabric  is  first  dyed  of 
a  uniform  color,  and  then  the  form  of  the  desired  pattern  is  compressed  upon  the  cloth 
with  stamps  coated  with  some  substance  containing  a  very  weak  acid.  An  acid  known  as 
citric  acid  (a  crystalline  solid),  mixed  with  gum,  is  generally  used  for  this  purpose.  Tho 
fabric  is  now  dried,  and  still  exhibits  an  uniform  color.  No  sooner,  however,  is  it  dipped 
in  a  weak  solution  of  chloride  of  lime,  than  the  citric  acid  sets  up  just  that  amount  of  local 
decomposition  necessary  to  affect  the  liberation  of  the  chlorine,  which  immediately 
bleaches  out  the  stamped  pattern,  leaving  the  unstamped  portions  of  the  fabric  unchanged. 
The  material  which  thus  effects  the  liberation  of  chlorine,  is  termed  a  mordant,  and  tha 
operation  is  called  '•'•mordanting" — FARADAY. 

QUESTIONS. — Enumerate  some  of  the  results  which  have  followed  the  discovery  and 
application  of  chlorine.  What  is  the  natural  state  of  cotton  fibers?  What  are  the  suc- 
cessive operations  of  a  modern  bleachery  ? 


252  INORGANIC     CHE  MIS  TRY. 

axis,  the  wheel  is  caused  to  rotate  rapidly,  and  the  cloth,  by  agitation  and 
dashing  of  the  water,  is  speedily  and  thoroughly  washed. 

FIG.  120. 


The  next  operation  consists  in  boiling  the  cloth  in  an  alkaline  solution, 
which  removes  all  the  greasy  and  resinous  matters.  This  is  effected  in  a  pe- 
culiar manner;  the  cloth  is  placed  in  large  rats,  on  a  grating,  or  perforated 
ialse  bottom,  through  which,  from  a  compartment  below,  rises  a  pipe,  furnished 
on  its  extremity  with  a  curved  iron  cover.  (See  Fig.  121.)  A  boiling  solu- 
tion of  alkali  is  forced,  by  steam  pressure,  from  the  compartment  below  the 
Tat  up  through  this  pipe,  and  striking  against  the  cover,  is  reflected  upon  the 
goods  in  the  form  of  a  shower ;  thence  filtering  through  the  texture  of  the 
cloth,  the  liquor  runs  back  into  the  lower  compartment,  to  be  again  heated  by 
steam,  and  forced  up  as  before.  This  process  is  continued  for  about  seven 
hours,  and  at  its  conclusion  the  color  of  the  cloth  is  darker  than  at  the  out- 
set. The  cloth  is  then  washed  again  in  the  wheels,  and  next  steeped  in  a 
very  dilute  solution  of  chloride  of  lime,  in  large  vats,  for  about  six  hours; 
it  even  then  is  not  white,  but  of  a  gray  appearance. 

In  the  next  process,  the  goods  are  steeped  for  four  hours  in  very  dilute 
sulphuric  acid,  when  a-  minute  disengagement  of  chlorine  takes  place  through- 
out the  substance  of  the  cloth,  and  it  immediately  assumes  a  bleached  ap- 
pearance. The  same  operations  of  washing,  boiling,  bleaching,  and  souring, 
are  then  successively  repeated,  in  less  time,  until  at  length  the  cloth  is  perfectly 
whitened. 

The  length  of  time  required  for  all  these  operations  is  from  24  to  4S  hours  ; 
one  parcel  of  goods  succeeding  another  in  each  successive  stage  of  the  pro- 


CHLORINE. 


253 


cess,  so  that  all  the  departments  of  a  bleachery  are  in  full  operation  at  tho 
same  time.  The  labor  of  handling  the  cloth,  which  may  seem  very  great,  is 
nearly  all  performed  by  machinery,  with  great  rapidity,  at  a  very  slight  ex- 
pense— the  average  cost  of  bleaching  cotton  fabrics  not  exceeding  one  cent 

FIG.  121. 


per  yard.     Cottons  subjected  to  bleaching  lose  about  10  per  cent,  in  weight 
Wool  is  bleached  by  washing,  and  exposure  to  the  vapor  of  burning  sulphur, 

SECTION   VI. 

IODINE. 

Equivalent,  127 '.     Symbol,  I.     Specific  gravity  of  vapor,  §*l. 

370.  History,— Iodine  was  discovered  in  1811  by  M. 
Courtois,  a  chemical  manufacturer  of  Paris. 

He  noticed  that  a  dark-colored  liquor,  left  after  the  preparation  of  soda 
from  the  ashes  of  sea-weeds,  powerfully  corroded  his  kettles,  and  that  when 
sulphuric  acid  was  added  to  the  liquor,  a  brown  substance  separated,  which 
on  the  application  of  heat  was  converted  into  a  violet-colored  vapor,  A  sub- 
sequent examination  showed  that  the  substance  in  question  was  a  new  ele- 
ment— Iodine. 

3*71.  Natural  History  — Iodine  is  widely,  but  sparingly  distributed 
in  nature.  In  the  inorganic  kingdom  it  is  a  constituent  of  all  sea-water,  of 
many  mineral  springs  (Saratoga,  Carlsbad,  etc.),  and  also  of  certain  Tare  min- 
erals. In  the  organic  kingdom,  it  exists  probably  in  all  marine  plants,  but 

QUESTIONS.— When  and  by  whom  was  iodine  discovered?  "What  circumstances  led  to 
its  discovery  ?  What  is  said  of  its  distribution  in  nature  ? 


254  INORGANIC    CHEMISTRY. 

more  abundantly  in  some  species  than  in  others ;  also  in  sponges,  in  the 
oyster  and  other  sea-inollusks,  and  in  some  fishes  (i.  &,  cod-li ver  oil).  It  is 
always  found  in  combination  with  other  substances — generally  as  iodide  of 
sodium,  or  magnesium. 

372.  Preparatio  n. — The  greater  part  of  the  iodine  of  commerce  is 
manufactured  at  Glasgow,  from  "  kelp,"  which  is  the  ashes  of  sea- weeds  col- 
lected and  burned  upon  the  coasts  of  Scotland  and  Ireland.     The  kelp  is 
treated  with  water,   which  dissolves  out  a  large  quantity  of  soluble  saline 
matters — carbonate  of  soda,  common  salt,  chloride  of  magnesium,  etc.     When 
these  substances  are  separated  from  the  solution  by  partial  evaporation  and 
crystallization,    there  remains  behind  a  dark-colored  liquor,  which  contains 
iodine.     This  is  heated  with  sulphuric  acid  and  peroxyd  of  manganese,  when 
the  iodine  distils  over  as  a  purple  vapor,  which  is  collected  in  receivers  and 
condensed  to  a  solid  by  cooling.     A  ton  of  kelp  yields  9  pounds  of  iodine. 
The  chief  uses  of  iodine  are  for  medicine,  photography,  and  to  some  extent  in 
dyeing. 

373.  Properties  . — Iodine,  at  ordinary  temperatures  and  pressures,  is 
a  solid,  arid  is  generally  obtained  by  crystallization  in  the  form  of  bluish-black 
scales,  which  possess  a  brilliant  and  somewhat  metallic  luster.     Exposed  to 
heat,  it  liquefies  at  225°  F.,  and  boils  at  350°,  forming  a  magnificent  purple 
vapor,  from  whence  it  derives  its  name  (iufyg,  violet-colored).     This  property 

p  12_  may  be  beautifully  illustrated  by  heating  a  few  grains  of 
iodine  hi  a  glass  flask,  or  test  tube,  over  a  spirit-lamp.  (See 
Fig.  122.)  On  withdrawing  the  heat  the  vapor  condenses, 
and  forms  brilliant  crystals  of  solid  iodine  upon  the  sides  of 
the  flask. 

Dropped  on  a  red  hot  surface  iodine  melts,  and  as  a  liquid 
assumes  the  spheroidal  state  (§  154),  forming  a  splendid  ex- 
periment. 

Iodine,  when  taken  inwardly,  acts  in  large  doses  as  an  ir- 
ritant poison ;  but  in  small  quantities  it  is  a  most  valuable 
medicine.  Long  before  its  discovery,  the  ashes  of  a  burnt 
sponge  were  often  prescribed  as  a  most  efficacious  remedy  for 
certain  diseases.  Their  effect  is  now  known  to  have  been 
due  to  the  iodine  contained  in  them.  Iodine  stains  the  skin  and  most  or- 
ganized substances  of  a  brown  color,  and  gradually  corrodes  them.  Water 
forms  with  it  a  yellow  solution,  but  dissolves  it  only  hi  very  small  quantity — 
1  part  in  7,000.  Its  bleaching  properties  are  very  feeble.  Alcohol,  ether, 
and  solutions  of  the  salts  of  iodine,  dissolve  it  freely. 

374.  Iodine  attacks  the  metals  rapidly.     Iron  or  zinc  placed  in  water  with 
it  are  readily  dissolved,  an  iodide  of  the  metal  being  formed.     Some  of  the 
combinations  of  iodine  with  the  metals  are  remarkable  for  their  brilliant 


QUESTIONS. — How  is  it  prepared  ?  What  are  its  properties  ?  From  what  circumstance 
does  it  derive  its  name  ?  What  are  the  effects  of  iodine  upon  the  animal  system  ?  What 
is  said  of  its  combinations  with  the  metals  ? 


BROMINE.  255 

colors.  An  illustration  of  this  forms  an  easy  and  striking  experiment.  Place 
in  three  test  tubes  a  solution  of  iodide  of  potassium  in  water  ;  if  we  add  to 
the  first  a  few  drops  of  a  solution  of  mercury  (corrosive  sublimate),  we  ob- 
tain a  beautiful  salmon-colored  precipitate,  which  almost  immediately  changes 
to  scarlet.  A  solution  of  sugar  of  lead  added  to  the  second,  produces  a  bright 
yellow  precipitate  ;  and  a  solution  of  subnitrate  of  mercury  added  to  the 
third,  a  green  precipitate. 

The  distinctive  test  for  iodine  is  a  solution  of  starch,  with  which  it  strikes 
a  deep  blue  color.  The  solution  must,  however,  be  cold,  and  no  alkali  must 
be  present.  This  may  be  illustrated  by  experiment  as  follows  :  —  Draw  or 
paint  upon  a  sheet  of  paper,  figures  in  starch  paste,  and  expose  the  paper  to 
the  vapor  arising  from  iodine  thrown  upon  a  hot  surface.  The  figures,  which 
were  before  colorless,  immediately  bedome  blue.  If  a  little  of  the  tincture  of 
iodine  be  dropped  upon  flour,  potatoes,  etc.,  the  presence  of  starch  in  these 
bodies  will  be  indicated. 

Iodine  unites  with  hydrogen  to  form  an  acid,  hydriodic  acid,  Til,  and  with 
oxygen,  in  several  proportions,  to  form  both  oxyds  and  acids.  Its  principal 
oxygen  compound  is  iodic  acid,  IDs. 

The  most  important  compound  of  iodine  is  that  which  results  from  its  union 
with  potassium,  forming  a  white  crystallizable  salt,  the  iodide  of  potassium, 
also  termed  the  "  hydriodate  of  potash"  (KI).  It  is  in  this  condition  that 
iodine  is  chiefly  used  in  medicine,  and  also  in  photographic  operations. 

SECTION    VII. 


Equivalent  80.     Symbol,  Br.     Specific  gravity  of  vapor,  5  '3. 

375.  History  —  Bromine  was  discovered  by  M.  Ballard, 
a  French  chemist,  in  1826,  in  the  "  mother/'  or  residual 
liquor  left  after  the  crystallization  and  separation  of  the 
salts  of  sea-  water. 

376.  Distribution  .  —  It  exists  in  all  sea-  water  in  minute  quantity, 
generally  in  the  proportion  of  about  one  grain  to  the  gallon;  and  for  the 
most  part  in  combination  with  magnesium,  forming  bromide  of  magnesium. 
It  is  also  found  in  certain  mineral  springs,  and  in  a  few  minerals. 

377.  Preparation  .—-Bromine  is  prepared  by  passing  into  the  mother 
liquor  of  sea-water  a  stream  of  chlorine  gas,   and   then  agitating  the  liquor 
with  ether.     The  chlorine  sets  the  bromine  free  from  its  combinations,  and 
the  ether  dissolves  it.     After  standing  for  a  little  time,  the  etherial  solution, 
having  a  fine  red  color,  separates  and  floats  at  the  top. 

378.  Properties  ,  —  Bromine,  at  ordinary  temperatures  and  pressures, 


QUESTIONS.— What  is  the  distinctive  test  of  iodine?  What  is  the  principal  salt  of 
iodine  ?  When  and  by  whom  was  bromine  discovered  ?  What  is  said  of  its  distribution 
in  nature  ?  How  is  bromine  obtained  ?  What  arc  its  properties  ? 


256  INORGANIC    CHEMISTRY, 

is  a  red  liquid,  so  deep  in  color  as  to  be  nearly  opaque,  It  is  extremely  vola> 
tile,  and  can  only  be  preserved  in  very  close  vessels.  A  few  drops  slightly 
warmed  in  a  glass  flask,  will  fill  the  vessel  with  blood-red  vapors*  Its  odor 
is  somewhat  like  chlorine,  but  more  offensive }  hence  the  name  Bpw//or,  lad 
odor.  When  swallowed,  it  acts  as  a  deadly  poison,  and  a  single  drop  upon 
the  beak  of  a  bird  is  said  to  occasion  instant  death,  It  rapidly  destroys  all 
organic  tissues,  and  stains  the  skin  permanently  yellow.  It  boils  at  145°  F., 
and  when  exposed  to  a  cold  of  -—10°  F,,  freezes  into  a  crystalline  solid* 
Bromine  bleaches  like  chlorine,  is  slightly  soluble  in  water,  but  dissolves  freely 
in  alcohol  and  ether.  It  combines  directly  with  many  of  the  metals,  and 
forms  bromides— the  act  of  combination  being  often  accompanied  with  an  ex- 
plosive evolution  of  light  and  heat.  This  may  be  experimentally  shown  by 
cautiously  pouring  a  small  quantity  of  powdered  antimony  or  tin  upon  a  few 
drops  of  bromine  contained  in  a  deep  strong  glass.  In  short,  the  properties 
of  bromine  greatly  resemble  those  of  chlorine,  but  they  are  less  strongly 
developed, 

Bromine  is  extensively  used  in  photographic  processes,  and  sometimes  in 
medicine. 

But  one  compound  of  bromine  and  oxygen1  is  known,  viz.,  bromic  acid, 
BrOs )  it  also  unites  with  hydrogen  to  form  an  acid,  hydrobromic  acid,  HBr. 

SECTION     VIII, 

F  Ltf  ORItf  U. 
Equivalent^  19,     Symbol^  F",     Theoretical  Density,  1'3 1, 

879.  History,  —  Of  this  element  but  little  is  known 
except  from  its  compounds. 

Its  affinities  for  the  other  elements  are  so  powerful,  and  its  action  on  the 
human  system  is  so  deleterious,  that  its  isolation  has  been  regarded  as  almost 
impossible.  Within  a  comparatively  recent  period,  however,  several  chemists 
have  succeeded  in  separating  it  from  all  other  bodies,  in  the  form  of  a  colorless 
gas.  In  its  general  nature  and  properties  it  undoubtedly  resembles,  and  is 
closely  allied  to,  chlorine,  bromine,  and  iodine. 

The  only  compound  in  which  it  exists  in  nature  in  any  abundance,  is  a. 
compound  of  lime,  called  fluorspar,  or  fluoride  of  calcium.  This  mineral  is 
found,  in  great  quantity  and  beauty,  in  Derbyshire,  England,  and  from  it 
the  well-known  ornaments  known  as  "Derbyshire  spar,"  are  manufactured. 
Fluorine  is  also  found  in  a  great  variety  of  other  minerals,  and  exists  in  mi- 
nute quantities  in  the  bones  of  animals,  and  in  the  enamel  of  the  teeth. 

Compounds  containing  fluorine  can  be  decomposed  without  difficulty,  and 
the  fluorine  transferred  from  one  body  to  another ;  but  so  great  is  its1  affinity 
for  the  metals,  and  for  silicon,  a  constituent  of  glass,  that  in  passing  out  from 


QUESTIONS. —How  docs  bromine  act  upon  the  metals?  What  are  its  Uses ?  What  itd 
compounds  ?  What  is  known  of  fluorine  ?  What  is  said  of  its  distribution  in  nature  ? 
Why  is  it  difficult*)  isolate  fluorine  ? 


FLUORINE.  257 

a  state  of  combination,  it  combines  again  immediately  with  the  material  of 
the  vessel  containing  it. 

379.  Hydrofluoric  Acid,  HF,— Fluorine  is  not  known  to 
unite  with  oxygen  under  any  circumstances,  but  with  hy- 
drogen it  forms  a  very  remarkable  compound,  "  hydroflu- 
oric acid." 

This  substance  is  formed  by  heating  powdered  fluor-spar  with  strong  sul- 
phuric acid,  in  a  platinum  or  lead  retort,  furnished  with  a  receiver  of  the  same 
metal,  which  is  kept  cool  by  immersion  in  a  freezing  mixture.  The  chemical 
reaction  which  takes  place  may  be  expressed  as  follows : — 

Fluoride  of  calcium.    Sulphuric  Acid.  Snip.  lime.         Hydrofluoric  acid. 

CaF     +    S03  HO    —    CaO,  S03    -f     HF 

The  acid  thus  obtained  is  a  gas  at  ordinary  temperatures,  but  is  condens- 
ible  by  cold  into  a  volatile,  colorless  liquid,  which  evolves  white,  suffocating 
fumes  on  exposure  to  the  air;  its  attraction  for  water  is  very  great,  and 
when  poured  into  it,  it  hisses  like  a  red-hot  iron.  As  vapor,  and  as  an 
aqueous  solution,  it  attacks  and  readily  dissolves  glass,  and  all  compounds 
containing  silica,  together  with  some  mineral  substances  that  no  other  acid 
can  affect.  This  property  is  often  made  available  for  etching  upon  glass. 

In  its  most  concentrated  form,  hydrofluoric  acid  is  a  most  dangerous  sub- 
stance, and  is  more  destructive  of  animal  tissues  than  any  other  known  agent. 
The  most  minute  drop  upon  the  skin  occasions  a  deep  and  painful  burn,  often 
terminating  in  an  ulcer  difficult  to  cure.  Its  vapor  is  also  in  the  highest  de- 
gree corrosive. 

The  peculiar  action  of  hydrofluoric  acid  vapor  upon  glass  may  be  easily  illus- 
trated without  danger,  by  the  following  experiment.  Place  in  a  small  leaden, 
dish,  or  an  earthen  cup,  the  interior  of  which  has  been  slightly  oiled,  a  little 
powdered  fluor-spar,  and  add  strong  sulphuric  acid,  FIG.  122. 

sufficient  to  form  with  it  a  thin  paste.  Cover  the  cup 
with  a  piece  of  window-glass  which  has  received 
a  coating  of  wax,  and  from  some  parts  of  which 
the  wax  has  been  removed,  by  scratching  with  a 
needle  or  other  pointed  instrument.  (See  Fig.  122.) 
After  the  lapse  of  some  hours,  remove  the  wax  by 
melting  and  washing  with  oil  of  turpentine,  when  those  parts  of  the  glass  left 
bare  will  be  found  to  be  deeply  corroded.  The  same  result  can  also  be  ob- 
tained in  the  course  of  a  few  minutes,  by  a  gentle  application  of  heat  to  the 
cup  containing  the  mixture. 

QUESTIONS. — What  is  its  most  remarkable  compound  ?  How  is  it  prepared  ?  What  are 
its  properties  ?  How  does  it  act  upon  organic  substances  ?  How  may  its  action  on  glass 
be  illustrated? 


258  INORGANIC     CHEMISTRY. 

SECTION    IX. 

SULPHUR. 

Equivalent,  16.     Symbol,  S.     Specific  gravity,  T98,  in  vapor,  6.65. 

380.  Natural  History  and  Distribution.  —  Sulphur  is 
an  element  abundantly  distributed  in  nature,  most  exten- 
sively as  a  mineral  product,  but  widely  and  in  small  quan- 
tities as  a  constituent  of  animals  and  vegetables.     It  has 
been  known  from  the  most  remote  antiquity. 

Sulphur  is  found  in  a  native,  or  uncombined  state,  in  all  volcanic  districts ; 
and  in  Sicily  and  in  some  parts  of  South  America,  it  exists  in  immense  beds 
in  the  earth.  Many  of  the  compounds  of  sulphHir  with  the  metals  occur  as 
natural  productions  in  great  abundance,  especially  the  sulphurets  (sulphides) 
of  iron,  copper,  lead,  and  zinc.  The  sulphuret  of  iron  (iron-pyrites)  is  even 
employed  as  a  source  of  sulphur.  In  an  oxydized  condition,  as  sulphuric  acid, 
it  is  still  more  widely  diffused  in  combination  with  various  earths,  as  the 
sulphates  of  lime,  magnesia,  baryta,  etc.  Nearly  one  half  the  weight  of  sul- 
phate of  lime  (gypsum,  or  plaster  of  Paris)  Is  sulphur. 

381.  Most  of  the  sulphur  used  in  the  arts  is  obtained  from  Sicily  and  the 
volcanic  districts  of  southern  Italy,  the  former  exporting  about  1,540,000 
cwts.  yearly,     It  is  generally  subjected,  on  the  spot  where  it  is  dug  from  the 
earth,  to  a  rough  purification  by  fusion,  and  is  brought  into  commerce  in  the 
form  of  amorphous,  or  semi-crystalline  masses.     Another  commercial  form  is 
roll  sulphur,  or  brimstone,  which  is  generally  the  produce  of  roasting  the 
sulphurets  of  iron  and  copper  (pyrites),  collecting  the  evolved  fumes  in  con- 
densing chambers,  and  subsequently  fusing  the  sulphur  into  sticks.    "  Flowers 
of  sulphur,"  a  powder,  is  a  third  commercial  state  which  this  element  is  made 
to  assume ;  and  is  produced  by  distilling  sulphur  and  condensing  the  vapor. 

382.  Properties . — Sulphur  in  its  ordinary  condition  is  a  yellow,  brit- 
tle solid,  which,  by  warmth  and  friction,  emits  a  characteristic  odor  (brim- 
stone odor).     It  is  insoluble  in  water,  and  consequently  tasteless ;  it  is  very 
slightly  soluble  in  alcohol  and  ether ;  more  so  in  oil  of  turpentine  and  some 
other  oils;  and  readily  in  the  bisulphide  of  carbon.     It  is  a  bad  conductor  of 
heat ;  and  a  roll  of  sulphur,  when  grasped  by  the  warm  hand,  crackles  and 
frequently  falls  in  pieces  from  unequal  expansion.     It  is  a  non-conductor  of 
electricity,  but  when  rubbed  develops  negative  electricity  abundantly. 

Sulphur  is  highly  inflammable,  burning  with  a  blue  flame,  and  emitting 
suffocating  fumes  of  sulphurous  acid,  (the  familiar  odor  of  a  match).  It  has  a 
powerful  affinity  for  most  of  the  other  elements,  and  its  act  of  combination 

QUESTIONS. — What  is  the  history  of  sulphur  ?  What  is  said  of  its  distribution  in  na- 
ture? From  whence  are  supplies  of  Bulphur  chiefly  derived  ?  What  are  its  commercial 
forms  ?  What  are  the  properties  of  sulphur  ?  What  is  said  of  its  solubility  ?  What  of 
its  affinity  for  other  elements  ? 


SULPHUR.  259 

with  the  metals  to  form  sulphides,  or  sulphurets,  is  often  attended  with  an 
evolution  of  light  and  heat.  This  fact  may  be  experimentally  illustrated  by 
placing  in  a  flask  a  few  fragments  of  sulphur,  and  above  them  some  copper 
turnings;  on  the  application  of  heat  from  a  spirit-lamp,  vapor  of  sulphur 
rises,  and  coming  in  contact  with  the  copper,  enters  into  vivid  combination 
with  it. 

383.  Allotropism  of  Sulphur,— One  of  the  most  re- 
markable characteristics  of  sulphur  is  its  allotropism,  or 
power  of  existence  in  different  states. 

The  first  indication  of  this  power  is  perhaps  to  be  found  in  the  fact,  that  it 
is  capable  of  assuming  two  distinct  crystalline  forms.     These  are  not  merely 
modifications  of  one  original  primary  figure  (to  which  cause  most  crystalline 
variations  can  be  referred),  but  they  belong  to  two  different,  in-    ;pIG.  ^23. 
convertible,   and  incompatible   systems  of  crystallization,   viz., 
oblique  rhombic  prisms  and  right  rectangular  prisms.     Examples 
of  the  first  form,  Fig.  123,  (octohedrons  derived  from  oblique 
rhombic  prisms),  occur  in  native  sulphur,  or  in  sulphur  crystal- 
lized from  a  solution.  t  Examples  of  the  second  form  may  be  ob- 
tained by  melting  a  quantity  of  sulphur  in  an  earthen  crucible, 
and  allowing  it  to  solidify  on  the  surface ;  if  the  crust  be  then 

F       124  pierced  with  a  hot  wire,  the  fluid  portion  beneath  may 

be  poured  off,  when  the  interior  of  the  crucible,  on  cool- 
ing, will  be  found  to  be  lined  with  slender  needles,  or 
right  rectangular  prisms.  (See  Fig.  124.) 

Both  forms  of  crystals  may  be  obtained  by  dissolving 
!  sulphur  in  boiling  oil  of  turpentine ;  as  the  solution  cools, 
the  sulphur  crystallizes  out,  first  in  the  form  of  prisms ; 
but  afterward,  as  the  temperature  is  reduced,  octohedra 
are  formed. 

The  power  possessed  by  sulphur,  of  manifesting  itself  under  two  condi- 
tions, is,  however,  most  strikingly  illustrated  by  certain  phenomena  of  its 
melting  and  subsequent  cooling.  Thus,  if  we  heat  a  small  quantity  of  sulphur 
in  a  glass  flask  over  a  spirit-lamp,  it  melts  at  a  temperature  of  250-280°  F., 
into  a  clear,  yellow  liquid.  If  a  portion  of  this  liquid  be  poured  into  cold 
water,  It  immediately  condenses  into  the  state  it  had  before  melting — that  is, 
into  common,  yellow,  brittle  sulphur.  If  to  the  portion  remaining  in  the 
flask  a  stronger  heat  be  applied  (about  500°  F.),  the  transparent  fluid  gra- 
dually thickens,  becomes  brown  at  first,  and  at  last  nearly  black  and 
opaque ;  in  this  condition  the  viscidity  of  the  sulphur  is  such,  that  the  flask 
may  be  inverted  without  escape  of  its  contents.  If  the  heat  be  still  further  in- 
creased, the  black,  tenacious  sulphur  once  more  liquefies,  though  it  never  be- 


QTTESTIONS. — What  is  said  of  the  allotropism  of  sulphur  ?  What  is  the  first  indication 
of  this  property  ?  In  what  two  forms  does  sulphur  crystallize  ?  What  are  examples  ? 
In  what  other  way  may  the  allotropic  properties  of  sulphur  be  illustrated  ? 


260 


INORGANIC     CHEMISTRY. 


comes  as  fluid  as  when  first  melted,  at  the  temperature  of  250°  F.,  and  if 
suddenly  cooled,  by  pouring  it  in  a  slender  stream  into  cold  water,  it  assumes 
a  most  singular  state.  It  is  no  longer  yellow  and  brittle,  like  ordinary  sul- 
phur, or  like  the  product  of  pouring  into  water  the  first  result  of  fusion,  but 
it  remains  soft,  tenacious,  highly  elastic,  and  of  a  brown  color,  resembling,  in 
ah1  its  external  characteristics,  strips  of  India  rubber  or  gutta  percha.  In  this 
form  it  can  be  molded  by  the  hand,  and  may  be  used  to  take  impressions  of 
seals,  medallions,  etc.  After,  the  lapse  of  a  little  time,  it  again  becomes  yel- 
low, and  returns  to  its  original  brittle  condition,  giving  out  in  the  transforma- 
tion a  quantity  of  latent  heat. 

384.  Milk    of   S  u  1  p  h  u  r  — If  we  add  to  a  strong  boiling  solution  of 
potash  or  soda,  a  little  of  the  flowers  of  sulphur,  a  part  of  the  sulphur  dis- 
solves, and  imparts  to  the  liquor  a  yellowish-brown  color.     If  a  little  of  the 
clear  solution  be  added  to  water,  slightly  acidulated,  the  acid  wih1  unite  with  the 
alkali  holding  the  sulphur  in  solution,  and  cause  the  sulphur  to  be  precip- 
itated in  the  form  of  exceedingly  minute  particles,  giving  to  the  water  a 
milky  appearance.     Sulphur  in  this  form  is  nearly  white  in  appearance,  and 
is  known  as  "  Milk  of  Sulphur,"  or  "Precipitated  Sulphur." 

In  the  organic  kingdom  sulphur  is  extensively,  and  perhaps  universally 
diffused  throughout  animal  substances,  and  exists  in  small  quantities  in. 
most  vegetables.  The  well-known  blackening  of  a  silver  spoon  immersed  for 
some  time  in  a  boiled  egg,  is  due  to  the  presence  of  sulphur  in  the  egg.  The 
presence  of  sulphur  also  in  a  piece  of  flannel  may  be  strikingly  demonstrated 
by  immersing  the  cloth  in  a  mixture  of  oxyd  of  lead  in  a  solution  of  potash  ; 
on  applying  heat,  the  flannel  immediately  turns  black. 

385.  Compounds  of  Sulphur  and  Oxygen , — The  compounds 
of  sulphur  with  oxygen  are  numerous,  but  only  two  of  them  demand  an  ex- 
tensive notice ;  these  are  Sulphurous  acid,  SOj,  formed  by  the  union  of  one 

equivalent  of  sulphur  with  two  of  oxygen ;  and 
Sulphuric  acid,  SOs,  formed  by  the  union  of  one  of 
sulphur  and  three  of  oxygen. 

386.  Sulphurous  Acid,  S02  is  form- 
ed when  sulphur  is  burned  in  oxy- 
gen (See  Fig.  125)  or  atmospheric  air  ; 
and  is  the  occasion  of  the  well-known 
suffocating  odor  of  an  ignited  match. 
It  exists  in  nature  in  the  vicinity 
|  of  volcanoes,  and  is  often  evolved 
in  immense  quantities  from  their 
craters. 


FIG.  125. 


QUESTIONS— What  is  milk  of  sulphur?  What  is  said  of  sulphur  in  the  organic 
kingdom  of  nature?  What  are  illustrations  of  its  presence  in  animal  suhstances? 
What  is  said  of  the  compounds  of  sulphur  with  oxygen  ?  What  of  sulphurous  acid  ? 


SULPHUR. 


261 


FIG.  126. 


When  required  in  a  pure  state,  it  is  best  pre- 
pared by  depriving  oil  of  vitriol  of  a  part  of  its 
oxygen.  In  order  to  effect  this,  two  or  three 
ounces  of  concentrated  sulphuric  acid  are  boiled 
in  a  glass  retort  or  flask,  with  a  half  an  ounce 
of  copper  turnings ;  pieces  of  charcoal  may  be 
substituted  in  place  of  the  copper,  but  the  gas 
evolved  under  such  circumstances  is  not  pure. 
In  this  process,  a  part  of  the  acid  gives  up  one 
equivalent  of  its  oxygen  to  the  metal,  and 
sulphurous  acid  gas  is  liberated  ;  the  oxyd 
of  the  metal  produced,  unites  with  a  portion 
of  undecomposed  acid  to  form  a  sulphate. 
Thus:— 

Copper.  Sulph.  acid.      Sulph.  copper.  Sulphurous  acid, 

Ca  +  2S03  =>  CaO,  S03  +  S02. 

By  allowing  the  gas  to  bubble  through  water,  a  strong  solution  will  be  ob- 
tained, which  may  be  used  for  illustrating  the  properties  of  sulphurous  acid. 

387.  Properties  , — Sulphurous  acid  is  a  colorless  gas,  with  a  charac- 
teristic odor,  easily  condensible  by  cold  or  by  pressure,  into  a  colorless,  limpid 
liquid.  "Water,  at  60°  F.,  absorbs  from  40  to  50  times  its  volume  of  sulphur- 
ous acid,  and  forms  thereby  a  strongly  acid  liquid.  Hence  it  is  necessary  to 
collect  this  gas  over  mercury  or  by  the  displacement  of  air  from  dry  vessels. 
Its  avidity  for  water  is  so  great,  that  a  piece  of  ice  introduced  into  a  jar  of 
it,  is  instantly  liquefied. 

Sulphurous  acid  is  not  inflammable,  and  a  lighted  candle  immersed  in  a 
jar  of  the  gas,  is  immediately  extinguished  for  the  want  of  free  oxygen.  A 
most  certain  way  of  extinguishing  a  chimney  on  fire  is  to  scatter  flowers  of 
sulphur  on  a  pan  of  coals  in  a  fireplace-opening  beneath.  The  sulphurous 
acid  gas  formed  by  the  combustion  of  the  sulphur,  ascends  the  flue,  expels 
the  atmospheric  air  present  in  it,  and  by  depriving  the  burning  soot  of  free 
oxygen,  extinguishes  it. 

Sulphurous  acid  possesses  bleaching  properties,  and  is  extensively  employed 
in  bleaching  straw  and  wool.  The  articles  are  moistened  and  suspended  in 
closed  chambers  in  which  sulphur  is  burned  in  an  open  dish ;  (an  inverted 
barrel  is  often  made  to  subserve  the  purpose  of  a  bleaching  chamber.)  The 
sulphurous  acid  is  absorbed  by  the  damp  goods,  and  discharges  their  color. 
The  bleaching  action  appears  to  be  due  to  the  fact,  that  the  gas  unites  with 
the  coloring  matters  to  form  colorless  compounds.  It  does  not,  like  chlorine,  '« 
decompose  and  destroy  the  coloring  matter,  since  by  the  action  of  a  stronger 
chemical  agent,  the  colorless  compound  may  be  broken  up  and  the  original 


QUESTIONS.— How  is  it  usually  prepared?  Give  the  chemical  reaction  involved  in  its 
preparation.  What  are  its  properties  ?  What  are  its  relations  to  combustion  1  How  is 
sulphurous  acid  employed  in  bleaching  ?  What  is  the  nature  of  its  bleaching  action  ? 


262  INORGANIC    CHEMISTRY. 

color  restored.  This  may  be  illustrated  by  holding  a  red  rose,  or  any  other 
red  flower,  over  a  bit  of  burning  sulphur.  The  color  is  speedily  discharged, 
but  may  be  again  restored  by  washing  with  dilute  sulphuric  acid.  White 
flannel  which  has  been  bleached  by  sulphurous  acid,  when  washed  for  the 
first  time  with  an  alkaline  soap,  has  its  original  yellow  color  in  part  restored 
to  it. 

Sulphurous  acid  is  also  valuable  as  a  disinfecting  agent. 

The  compounds  of  sulphurous  acid  with  the  bases  are  termed  sulphites. 
They  are  readily  formed  by  transmitting  a  stream  of  gas  through  water  in 
which  the  oxyd  or  the  carbonate  of  the  metal  is  dissolved  or  suspended,  the 
carbonates  being  decomposed  with  effervescence.  The  sulphite  of  soda  is 
known  in  commerce  as  antichlorine ;  since  its  solution  in  water  is  able  to 
neutralize  the  chlorine  which  may  remain  in  fabrics  after  bleaching,  and  thus 
prevents  its  destructive  action. 

388.  Sulphuric    Acid,    S  Os. — This  acid  is  one  of  the  most  impor- 
tant of  all  chemical  reagents,  and  furnishes  the  means  by  which  most  other 
acids  are  prepared.     Immense  quantities  of  it  are  consumed  in  the  manu- 
facture of  carbonate  of  soda,,  nitric  and  hydrochloric  acids,  chlorine,  alum,  sul- 
phate of  copper  (blue  vitriol),  stcariue,  phosphorus,  etc.,  and  in  dyeing,  and 
in  the  refining  of  the  precious  metals.     Its  annual  consumption  in  Great 
Britain  alone  is  upward  of  twenty  millions  of  pounds. 

389.  Preparation . — It  has  been  already  stated,  that  when  sulphur  is 
burned  in  air,  or  oxygen,  the  product  is  sulphurous  acid.     This  gas,  if  made 
to  combine  with  half  as  much  oxygen  again  as  it  already  contains,  is  converted 
into  sulphuric  acid;  thus  S02+0==S03.     In  other  words,  sulphurous  acid 
must  be  oxydized  in  order  to  enable  us  to  form  sulphuric  acid.     Oxygen  and 
sulphurous  acid  can  not,  however,  be  made  to  unite  directly,  but  the  inter- 
vention of  some  third  substance  is  necessary.     In  the  presence  of  water,  the 
union  takes  place  slowly,  or  if  the  two  gases  be  mixed,  and  passed  over 
spongy  platinum,  the  union  is  effected  immediately. 

Neither  of  these  processes  can,  however,  be  used  with  advantage  in  the 
arts ;  and  the  manufacture  of  sulphuric  acid  upon  a  large  scale  depends 
upon  the  fact,  that  when  sulphurous  acid  mixed  with  oxygen  is  brought  in 
contact  with  deutoxyd  of  nitrogen  (NOa),  or  any  of  the  other  higher  oxyds 
of  nitrogen,  combination  takes  place  with  great  rapidity ;  the  presence  of  a 
very 'small  proportion  of  deutoxyd  of  nitrogen  being  moreover  sufficient  to 
effect  the  combination  of  an  almost  indefinite  amount  of  sulphurous  acid  and 
oxygen,  provided  that  water  is  also  present. 

The  following  experiment  will  serve  to  illustrate  the  general  principle  upon 
which  sulphuric  acid  is  manufactured.  Burn  in  a  jar,  containing  a  little  water 
at  the  bottom,  a  piece  of  sulphur ;  as  a  consequence,  the  vessel  becomes  filled 
with  sulphurous  acid.  If  we  now  introduce  into  the  gas  a  shaving  moist- 

Q0E8TION8. — What  experiments  are  illustrative  ?  What  is  said  of  the  compounds  of 
sulphurous  acid  with  the  bases?  What  is  antichlorine?  What  is  said  of  sulphuric 
acid  ?  What  of  its  theoretical  preparation  ?  Upon  what  fact  does  its  practical  preparation 
depend  ?  How  may  it  be  experimentally  illustrated  ? 


SULPHU  R. 


263 


FIG.  128. 


ened  with  nitric  acid,  reddish-colored  fumes  will  immediately  form  around  the 
wood,  and  gradually  fill  the  whole  vessel.     (See  Fig.  127.)       pIG>  ^27, 
These  fumes  are  nitrous  acid,  and  are  produced  by  the  ac 
tion  of  the  sulphurous  acid,  which  decomposes  the  nitric  acid, 
and  by  depriving  it  of  1  equivalent  of  oxygen,  becomes  sul- 
phuric acid.     Thus : 

Sulphurous  acid.  Nitric  acid.  Sulphuric  acid.  Nitrous  acid. 

2S02   +   N05  =  2S03  -f    N03. 

The  vapor  of  the  sulphuric  acid  formed  is  absorbed  by  the 
water  in  the  jar,  and  by  repeating  the  experiment  several 
times,  a  quantity  of  dilute  sulphuric  acid  may  be  prepared. 

On  a  large  scale,  the  operation  of  manufacturing  sulphuric  acid  is  essen- 
tially the  same  in  principle,  and  may  be  described  as  follows:  immense 
chambers,  lined  with  lead,  are  constructed ;  in  some  instances  300  feet  long, 

15  feet  high,  and  20 
broad.  (See  Fig.  128.) 
The  floor  of  these  cham- 
bers is  covered  to  the 
depth  of  a  few  inches 
with  water,  and  at  one 
extremity  there  is  ad- 
mitted by  a  suitable  flue,  B,  sulphurous  acid  (from  a  furnace  of  burning  sul- 
phur), with  atmospheric  air ;  by  another  pipe,  A,  steam ;  and  by  a  third,  C, 
vapors  of  nitric  acid  (obtained  by  heating  nitrate  of  soda  with  strong  sul- 
phuric acid).  When  these  several  substances  meet  within  the  chambers  a 
most  interesting  and  curious  series  of  reactions  take  place  ; — the  sulphurous 
acid  withdraws  oxygen  from  tho  nitric  acid  vapor,  NO5,  and  converts  it  into 
deutoxyd  of  nitrogen,  NO-2,  itself  changing  into  sulphuric  acid,  S03.  This 
last  product  then  uniting  with  the  steam,  is  precipitated  to  the  bottom  of  the 
chamber,  and  is  absorbed  by  the  water.  The  deutoxyd  of  nitrogen  does  not 
remain  unaltered,  but  in  contact  with  the  air  admitted  into  the  chambers, 
absorbs  two  equivalents  of  oxygen,  and  becomes  converted  into  peroxyd  of 
nitrogen,  N04,  forming  red  fumes  (§  347).  These  in  turn,  by  contact  with 
the  sulphurous  acid,  give  up  their  newly-acquired  oxygen  to  form  sulphuric 
acid,  and  are  reconverted  again  thereby  into  deutoxyd  of  nitrogen.  And 
this  process  is  repeated  over  and  over  again,  a  small  quantity  of  deutoxyd  of 
nitrogen  acting  as  the  intermediate  agent  for  withdrawing  oxygen  from  the 
air,  first  to  itself,  and  afterward  giving  it  up  to  oxydate  tho  sulphurous  acid. 
The  deutoxyd  of  nitrogen,  together  with  the  remaining  nitrogen  of  the  air, 
is  finally  allowed  to  escape  at  the  further  extremity  of  the  chambers,  and  a 
fresh  portion  of  nitric  acid  vapor  is  admitted  to  supply  its  place,  and  com- 
mence th*e  reactions  anew.  The  steam  admitted  into  the  chambers  does  not 
take  any  active  part,  but  its  presence  is  essential  to  the  success  of  the  opera- 


QTJESTIONS.— How  is  the  practical  manufacture  conducted  ?    What  reactions  take  place 
in  the  leaden  chambers  ? 


264  INORGANIC    CHEMISTRY. 

tion.*  The  chambers  in  which  the  acid  is  manufactured  are  usually  divided 
into  partitions,  in  order  that  tho  gases  may  mix  together  slowly  and  com- 
pletely, before  reaching  an  exit  tube  placed  at  the  farther  extremity. 

The  sulphuric  acid  which  collects  in  the  water  at  the  bottom  of  the  cham- 
bers, is  drawn  off  when  it  reaches  a  specific  gravity  of  about  1*5  ;  it  is,  how- 
ever, in  this  state  too  dilute  for  sale,  and  is  accordingly  evaporated  by  heat  in 
shallow  lead  pans,  until  it  becomes  strong  enough  to  corrode  the  lead,  when 
it  is  transferred  into  glass  or  platinum  retorts,  f  and  further  heated  until  it 
attains  a  specific  gravity  of  T84.  In  this  condition  it  constitutes  the  con- 
centrated oil  of  vitriol  of  commerce,  and  is  transported  in  carboys,  or  large 
glass  bottles  packed  in  boxes.  As  thus  produced,  it  is  a  definite  hydrate, 
composed  of  1  equivalent  of  acid,  and  1  of  water  (SOs,  HO).  This  proportion 
of  water,  amounting  to  three  ounces  in  every  pound  of  acid,  is  held  so  firmly 
that  it  can  not  be  driven  off  by  heat  (See  §  322.) 

390.  Nordhausen  Sulphuric  Acid , — In  early  times  sulphuric 
acid  was  obtained  by  distilling  dry  sulphate  of  iron  (green  vitriol)  in  earthen 
retorts,  at  a  high  temperature.  As  thus  prepared,  it  is  a  dark-brown,  thick, 
oily  liquid,  and  was  originally  called,  from  its  derivation,  "  oil  of  vitriol."  It 
is  the  most  concentrated  form  in  which  sulphuric  acid  can  exist  in  a  fluid 
condition,  and  contains  less  water  than  the  ordinary  concentrated  sulphuric 
acid.  When  exposed  to  the  air  it  fumes,  and  when  dropped  into  water, 
hisses  like  a  red  hot  iron.  As  acid  in  this  state  of  concentration  is  required 
for  certain  processes  in  the  arts,  it  is  still  prepared  in  the  old  way,  especially 
at  the  town  of  Nordhausen,  in  Saxony,  Germany; — hence  its  commercial 
name. 

Sulphuric  acid  is  known  to  combine  with  water  in  four  proportions,  forming 
four  definite  hydrates.  Their  composition  may  be  illustrated  as  follows : — 

Nordhausen  acid,  sp.gr 1-9 , 2(SOs)HO 

Oil  of  vitriol,  "     1-S4 80s,  HO 

Sulphuric  acid  of      "     1-78 SO3,HO-I-HO 

"  *«  "     1.63 SO3,HO  +  2HO(§274.) 


*  The  description  of  the  chemical  changes  involved  in  the  manufacture  of  sulphuric  acid 
in  the  leaden  chambers,  as  thus  given,  is  but  an  outline,  embracing  merely  the  funda- 
mental principles.  For  the  minute  details,  not  suited  for  an  elementary  work,  the  stu- 
dent is  referred  to  any  of  the  modern  encyclopedias  of  practical  science. 

t  It  was  originally  the  custom  to  concentrate  the  sulphuric  acid  by  boiling  it  in  glass 
vessels,  but  the  loss  from  breakage  is  so  great,  that  in  many  manufacturing  establish- 
ments platinum  stills  have  been  adopted,  this  metal  resisting  the  action  of  the  strongest 
acid  at  high  temperatures.  These  stills  are  constructed  in  Paris  of  thin  sheets  of  platinum 
soldered  with  gold.  They  are  oval  in  form  ;  and  as  a  protection  against  the  direct  action 
of  heat,  they  are  inclosed  in  iron  jackets.  Their  capacity  varies  from  500  to  2,000  pounds, 
and  their  cost  from  $8,000  to  $13,000  apiece;  and  although  one  of  these  vessels  only  en- 
dures for  a  period  of  two  or  three  years,  their  use  has  proved  more  economical  than 
glass. 

QUESTIONS.— What  is  the  density  of  the  acid  thus  formed  ?  To  what  processes  is  it 
subjected  ?  What  is  the  composition  of  concentrated  oil  of  vitriol  ?  What  is  Nordhausen 
sulphuric  acid  ?  What  are  its  properties  ?  How  many  hydrates  of  sulphuric  acid  are 
known? 


SULPHUR.  265 

391.  Anhydrous    Sulphuric  Acid . — When  Nordhausen  acid  is 
carefully  distilled  in  a  retort  furnished  with  a  receiver  kept  cool  by  a  freezing 
mixture,  white  fumes  pass  over,  which  may  be  condensed  into  a  white,  silky- 
looking,  fibrous  mass — anhydrous  sulphuric  acid.     This  substance   possesses 
no  acid  properties,  and  may  be  handled  without  danger.      When,  thrown 
into  water,  it  hisses,  and  forms  liquid  sulphuric  acid.     It  also  liquefies  on 
exposure  to  air,  by  the  absorption  of  moisture, 

392.  Propertie  s. — The  oil  of  vitriol  of  commerce  is  a  dense,  oily-look- 
ing liquid,  without  odor,  and  of  a  brownish  color.     It  is  the  strongest  of  all 
acids.    It  freezes  at  a  temperature  of — 29°  F.,  and  boils  at  620°  P.    Its  affin- 
ity for  moisture  is  most  intense,  and  it  abstracts  it  from  every  substance  with 
which  it  is  brought  in  contact.     If  a  quantity  of  strong  sulphuric  acid  be  ex- 
posed in  a  shallow  dish  to  the  air,  it  frequently  absorbs  sufficient  aqueous 
vapor  from  the  atmosphere  to  double  its  weight     A  piece  of  wood  introduced 
into  sulphuric  acid  becomes  black  and  reduced  to  coal,  the  same  as  if  it  had 
been  exposed  to  the  action  of  fire.     The  explanation  of  this  is  as  follows:  the 
wood  is  a  compound  of  oxygen,  hydrogen,  and  carbon ;  the  sulphuric  acid 
abstracts  the  oxv gen  and  hydrogen,  which  combine  to  form  water,  while  the 
carbon  remains  behind.     Gases  containing  aqueous  vapor  are  deprived  of  it 
by  causing  them  to  bubble  through  strong  sulphuric  acid. 

When  concentrated  sulphuric  acid  is  mixed  with  water,  great  heat  is 
evolved,  and  the  mixture,  when  cold,  occupies  less  bulk  than  the  two  liquids 
did  separately.  This  fact  may  be  strikingly  illustrated 
by  mixing  4  parts  of  oil  of  vitriol  with  1  of  water.  Water 
in  a  test  tube  immersed  in  such  a  solution,  may  be  caused 
to  boil  (See  Fig.  129.) 

Sulphuric  acid  does  not  evaporate  at  the  ordinary  tem- 
perature of  the  air ;  but  if  a  drop  of  dilute  acid  fall  upon 
a  cloth,  the  water  gradually  evaporates  until  the  acid 
which  is  left  behind  acquires  a  considerable  degree  of 
strength,  and  then  chars  or  destroys  the  cohesion  of  the 
fibers;  hence  the  destructive  action  of  sulphuric -acid 
upon  fabrics  even  when  very  much  diluted. — MILLER. 

Ordinary  sulphuric  acid  is  never  pure,  but  always  contains  lead  derived 
from  the  leaden  chambers ;  when  mixed  with  water,  this  lead  is  precipitated, 
and  causes  the  solution  to  appear  milky. 

Sulphuric  acid  attacks  all  the  metals  except  gold,  platinum,  iridium,  and 
rodium. 

393.  Hyposulphurous    Acid,    S2  02. — By  digesting  sulphur  with 


QUESTIONS. — What  is  anhydrous  sulphuric  acid  ?  What  arc  its  properties  ?  What  are 
the  properties  of  "  oil  of  vitriol  ?"  What  is  said  of  its  attraction  for  moisture  ?  What 
are  illustrations  of  this  ?  When  concentrated  sulphuric  acid  is  mixed  with  water,  what 
follows?  What  is  said  of  the  action  of  sulphuric  acid  on  fibers?  What  of  its  purity? 
What  of  its  action  on  metals?  What  is  said  of  hyposulphurous  acid  and  its  com- 
pounds? 


266  INOKGANIC    CHEMISTRY. 

a  solution  of  sulphato  of  soda,  a  portion  of  the  sulphur  is  dissolved,  and  a  salt 
containing  hyposulphurous  acid  is  formed — the  hyposulphite  of  soda.  The 
acid  itself  can  not  be  isolated.  Hyposulphite  of  soda  is  at  present  largely 
employed  in  photographic  operations,  owing  to  its  property  of  dissolving  cer- 
tain salts  of  silver  which  are  insoluble  in  water.  The  surface  of  the  photo- 
graph h  freed  from  them  by  immersion  in  a  solution  of  it  ;  after  which,  if  well 
washed  with  water,  it  is  no  longer  liable  to  alteration  by  exposure  to  light. 

394.  Sulphur  and  Hydrogen, 

Hydro  sulphuric  Acid,  IIS,  —  Sulphuretted  Hydrogen, 
Sulpliydric  Acid. — This  gas  is  formed  naturally  during 
the  putrefaction  of  many  organic  substances,  and  is  also  a 
constituent  of  many  mineral  springs.  It  is  easily  prepared 
by  the  action  of  dilute  sulphuric  acid  upon  protosulphide 
of  iron,  FS.° 

FIG  130  ^or  ^s  PurP°se   an   evolution   flask    (Fig.    130)   is  best 

adapted;  but  a  common,  open-mouthed  bottle,  fitted  with  a 
perforated  cork   and   bent  tube,   will 

/-I  TT  -101     \  T  1  JClG.     131. 

answer,      (bee  Iig.  131.)      Introduce 

into  the  flask  protosulphide  of  iron  in 

'  small  quantities,  with  water  sufficient 

to  cover  it ;  then  add  sulphuric  acid 

until  a  copious  disengagement  of  gas 

takes  place.    By  introducing  the  evolu- 
tion tube  into  cold  water,  a  solution  of 

tho  gas  will  be  obtained,  in  which  state  its  properties  may  be  ex- 
perimentally illustrated  to  the  best  advantage.  The  operation  of  preparing  the 
gas  should  be  conducted  in  a  well-ventilated  apartment,  or  in  the  open  air. 

The  chemical  reaction  involved  in  this  operation  is  as  follows :  water  is  de- 
composed; its  oxygen  uniting  with  the  iron  to  form  oxyd  of  iron,  which 
dissolves  in  the  acid  to  form  sulphate  of  iron,  while  the  hydrogen  escapes,  and 
takes  with  it  the  sulphur  contained  in  the  sulphide  of  iron.  Thus : — 

Sulphid*  ofiron.         Sulphuric  acid  (dilute).         Sulphate  of  iron.         Hydrosulph.  »dd. 

FeS      -f      S03,  HO      —      FeO,  S03      -{-     IIS. 

395.  Properties  . — Hydrosulphuric  acid  is  a  transparent,  colorless  gas, 
of  a  disgusting  odor,  like  that  of  rotten  eggs.     It  is  about  one  fifth  heavier 
than  common  air,  and  burns  with  a  blue  flame,  with  a  smell  of  stilphur.     It 
is  highly  poisonous  when  respired  in  a  concentrated  form,  and  even  when 


*  Protosulphuret  of  iron  is  prepared  by  heating  2  parts  of  iron  filings  with  \  \  parts  of 
sulphur,  to  a  red  heat,  hi  a  covered  earthen  crucible. 

QUESTIONS. — "What  of  hydrosulphuric  acid  ?  How  is  it  prepared  ?  "What  chemical  re- 
actions are  involved  in  ita  preparation  ?  What  is  said  of  its  properties  ?  What  of  its 
poisonous  effects? 


SULPHUR.  267 

present  in  the  air  in  very  minute  proportions,  it  is  rapidly  fatal  to  the  lower 
orders  of  animals.  A  single  gallon  of  it,  mixed  with  1,200  of  air,  will  render 
it  poisonous  to  birds,  and  1  in  100  will  kill  a  dog.  When  inhaled  it  acts  di- 
rectly upon  the  blood,  thickening  it,  and  turning  it  black.  It  is  this  gas  which 
makes  an  open  or  foul  sewer  so  destructive  of  health  to  any  district  in  which 
it  may  be  situated.  When  present  in  the  air  of  a  room,  it  may  be  instantan- 
eously destroyed  by  the  action  of  a  small  quantity  of  free  chlorine.  A  cloth 
moistened  with  alcohol,  and  held  before  the  mouth,  is  a  good  protection  also 
against  its  inhalation. 

By  pressure,  sulphuretted  hydrogen  is  reduced  to  a  colorless  liquid,  which 
freezes  at  — 122°  F.  into  a  crystalline,  semi-transparent  mass.  Cold  water 
dissolves  between  two  and  three  times  its  bulk  of  this  gas,  producing  a  feebly 
acid  liquid,  which  possesses  the  characteristic  smell  and  taste  of  sulphuretted 
hydrogen,  with  all  its  properties.  When  exposed  to  the  air,  this  solution  be- 
comes milky ;  the  hydrogen  being  slowly  oxydized  to  form  water,  while  the 
sulphur  separates.  The  solution,  therefore,  should  be  kept  in  well-stopped 
bottles,  quite  full. 

Sulphuretted  hydrogen  is  formed  naturally  under  a  variety  of  circumstances. 
Its  chemical  proportions  being  1  equivalent  of  hydrogen  (1)  to  1  of  sulphur 
(16),  it  follows  that  100  parts  of  the  gas  contain  only  about  6  parts  of  hy- 
drogen ;  so  that  a  very  small  proportion  of  hydrogen  causes  a  large  amount 
of  sulphur  to  assume  with  it  an  aeriform  condition,  and  exhibit  the  foetid  odor 
and  poisonous  properties  of  the  gas  in  question.  In  volcanic  countries  sul- 
phuretted hydrogen  is  often  evolved  from  fissures  in  the  rocks,  mixed  with 
steam  and  other  gases ;  in  sewers  and  cesspools  it  is  produced  in  large  quan- 
tities by  the  decay  of  organic  matter,  and  in  marshes,  where  vegetable  mat- 
ter alone  is  undergoing  decay,  in  the  presence  of  water  containing  sulphate 
of  lime  (gypsum),  its  presence  may  be  often  detected.  The  waters  of  mineral 
springs,  as  those  of  Avon  and  Sharon,  N.  Y.,  and  the  sulphur  springs  of 
Tirginia,  often  contain  sulphuretted  hydrogen,  though  rarely  in  a  proportion 
exceeding  1-J-  per  cent,  of  their  volume  ;  and  the  gas  in  solution  in  this  small 
quantity,  when  taken  into  the  stomach,  acts  as  a  valuable  medicinal  remedy 
for  various  diseases. 

Hydrosulphuric  acid,  though  a  feeble  acid,  combines  readily  with  bases  to 
form  sulphides,  or  sulphurets.  Thus,  if  we  place  a  drop  of  sulphuretted 
hydrogen  water  upon  a  bright  silver  or  copper  coin,  or  upon  a  piece  of  lead, 
a  black  spot  will  be  quickly  produced,  owing  to  the  formation  of  a  black 
compound  of  the  metal  and  sulphur  (a  sulphide).  The  black  sulphide  of  lead 
formed  when  hydrosulphuric  acid  is  brought  in  contact  with  the  salts  of  lead, 
is  particularly  noticeable,  and  may  be  exhibited  by  exposing  a  piece  of  paper 
moistened  with  acetate  of  lead  to  air  impregnated  with  this  gas.  This  test  is 
so  delicate,  that  1  part  of  sulphuretted  hydrogen  in  20,000  of  air  is  said  to 

QUESTIONS. — What  is  said  of  the  solubility  of  this  gas  ?  What  of  its  natural  formation 
and  proportional  composition  ?  What  is  said  of  its  presence  in  mineral  springs  ?  What 
of  its  combinations  with  the  metals  ? 


268  itfonoANic   CHEMISTRY. 


be  sufficient  to  occasion  a  blackening  of  the  paper.  For  the  same  reason, 
surfaces  covered  with  lead  paints,  in  the  vicinity  of  sewers,  cesspools,  or  the 
bilge'water  of  vessels,  etc.,  soon  become  discolored.  Sulphur  unites  with  zinc 
in  the  same  manner  as  with  lead,  but  the  resulting  compound,  sulphide  of 
zinc,  is  white,  and  not  dark  colored  like  the  sulphide  of  lead.  Hence  zinc 
paints,  for  many  locations,  are  more  suitable  than  lead  paints. 

"When  hydrosulphuric  acid,  either  in  the  form  of  gas  or  solution,  is  added 
to  a  solution  containing  copper,  silver,  gold,  lead,  tin,  antimony,  or  arsenic, 
these  metals  are  precipitated  as  insoluble  sulphides,  and  may  be  collected  and 
separated  from  the  solution  by  filtration.  If  iron,  zinc,  manganese,  cobalt, 
and  nickel  are  contained  in  the  same  solution,  they  are  not  precipitated  until 
a  stronger  reagent  is  added.  Hence  sulphuretted  hydrogen  may  be  used  to 
separate  one  class  of  metals  from  another  5  and  in  fact  is  employed  extensively 
for  this  purpose  in  chemical  analysis, 

SECTION    X. 

SELENIUM    AND    TELLURIUM, 

396.  Selenium,    Se  .  —  This  element  was  discovered  by  Berzelius  in 
1817,  and  was  named  by  him  Selenium,  from  Ze/b?^,  the  moon.     It  is  one  of 
the  least  abundant  of  the  elements,  and  always  occurs  in  combination,  gen- 
erally in  ores  of  iron,  copper,  and  silver,  forming  selenides  of  these  metals. 
The  principal  localities  in  which  it  exists  are  in  Norway,  Sweden,  and  the 
Hartz  mountains  of  Germany.     It  is  a  dark-brown,  brittle  solid,  opaque,  and 
possessing  a  metallic  luster  somewhat  like  lead.     It  closely  resembles  sulphur 
in  its  properties,  and  forms  acid  compounds  with  oxygen  (selenious  and  se- 
leuic  acids)  analogous  to  sulphurous  and  sulphuric  acids.     "When  heated 
strongly  it  gives  out  a  powerful  odor,  like  putrid  horse-radish,  by  means  of 
which  the  smallest  trace  of  this  element  may  be  detected  in  minerals,  when 
heated  before  the  blow-pipe. 

397.  Tellurium,    Te,isa  rare  substance,  found  chiefly  in  the  mines 
of  Hungary  and  Transylvania;  sometimes  native  and  nearly  pure,  but  gen- 
erally combined  with  various  metals,  such  as  gold,  silver,  bismuth  and  cop- 
per.     It  is  a  silver-  white,  brittle  solid,  possessing  a  strong  metallic  luster, 
and  by  some  authorities  is  classed  among  the  metals.     It  is,  however,  closely 
allied  to  sulphur  and  selenium  in  all  its  properties  and  combinations. 

Selenium  and  tellurium  both  unite  with  hydrogen  to  form  gaseous  com- 
pounds, of  singularly  offensive  and  noxious  properties.  A  single  bubble  of 
seleniuretted  hydrogen  allowed  to  escape  into  a  room,  produces  on  those  who 


QUESTIONS. — Why  do  surfaces  painted  with  lead  blacken  on  exposure  to  this  gasf 
"Why  are  zinc  paints,  for  many  situations,  preferable  to  lead  ?  Explain  the  manner  in 
which  hydrosulphuric  acid  is  used  in  chemical  analysis.  What  is  said  respecting  sele- 
nium ?  "What  are  its  characteristic  properties  ?  What  is  tellurium  ?  What  are  its  prop- 
erties ?  What  is  said  of  the  compounds  of  selenium  and  tellurium  with  hydrogen  f 
What  effect  has  tellurium  upon  the  animal  system  ? 


PHOSPHORUS.  269 

breathe  it,  all  the  usual  symptoms  of  a  severe  cold  and  irritation  of  the 
throat,  which  continue  for  several  days.  But  the  most  singular  fact  connected 
with  tellurium  is,  "  that  when  certain  odorless  preparations  of  this  element 
are  taken  internally,  they  form  compounds  within  the  animal  organization 
which  impart  to  the  breath  and  the  perspiration  so  foetid  an  odor  as  to  render 
the  person  taking  it  a  kind  of  horror  to  every  one  he  approaches ;  and  this 
lasts  sometimes  for  weeks,  though  the  dose  of  tellurium  administered  may  not 
exceed  a  quarter  of  a  grain." — JOHNSON. 

SECTION    XI. 

PHOSPHORUS. 

Equivalent,  32.     Symbol,  P.     Density,  1-863. 

398.  History ,— The  credit  of  the  discovery  of  phosphorus 
is  ascribed  to   Brandt,  an  alchemist  of  Hamburg,  who 
first   recognized  it  while   searching  for  the  philosopher's 
stone  in  human  urine,  in  the  year  1669.     Its  method  of 
preparation  was,  however,  for  a  long  time  kept  secret. 

399.  Natural    History    and    Distribution . — Phosphorus  is 
never  found  in  nature  in  a  free  state,  but  exists  in  small  quantities,  widely  dif- 
fused, in  the  mineral  kingdom,  principally  in  combination  with  lime.     It  is  a 
constituent  of  most  of  the  primitive  and  volcanic  rocks,  and  by  the  decay  of 
these  it  passes  into  the  soil ;  from  the  soil  it  is  extracted  by  plants,  which 
accumulate  it,  particularly  in  their  seeds  (wheat,  corn,   oats,  etc.).      Man 
and  animals  deriving  then*  support  directly  or  indirectly  from  plants,  in  turn 
collect  it  in  their  systems — in  such  quantities  that  animal  products  furnish 
almost  the  only  source  from  which  phosphorus  is  artificially  prepared.     United 
with  oxygen  and  with  lime,  it  forms  the  principal  mineral  constituent  of  the 
bones.     Thus  the  body  of  an  adult  man  contains  from  9  to  12  pounds  of 
bones,  which  contain  from  5  to  7  pounds  of  phosphate  of  lime  (phosphoric 
acid  and  lime),  or  from  1  to  2  pounds  of  pure  phosphorus.*     "  Phosphorus 

*  No  seed  suitable  to  become  food  for  man  and  animals  can  be  formed  in  any  plant  with- 
out the  presence  and  cooperation  of  the  phosphates,  and  a  field  in  which  phosphate  of 
lime,  or  the  alkaline  phosphates  form  no  part  of  the  soil,  is  totally  incapable  of  producing 
grain,  peas,  or  beans. 

Animals  which  are  fed  on  food  which  contains  no  phosphate  of  lime,  gradually  lose  their 
nervous  irritability,  and  sink  into  a  state  of  inanition  and  torpor,  which  is  speedily  followed 
by  death.  A  deficiency  of  phosphate  of  lime  in  the  food  of  young  children,  is  also  liable  to 
produce  a  disease  known  as  the  rickets.  As  animals  derive  the  phosphate  of  lime  neces- 
sary for  their  support  either  directly  or  indirectly  from  plants,  and  as  these  in  turn  ex- 
tract it  from  the  soil,  it  is  evident  that  the  fertility  of  a  soil  can  only  be  sustained  by  re- 
storing to  it  the  constituents  thus  abstracted  from  it.  Hence  the  value  of  bones  and 
animal  products  which  contain  phosphate  of  lime  (as  guano)  as  manures  for  wheat  and 
plants  of  like  character. 

QUESTIONS — What  is  the  history  of  phosphorus  ?  What  is  said  of  its  distribution  in. 
nature  ?  In  what  condition  does  it  exist  most  abundantly  ? 


270  INORGANIC     CHEMISTRY. 

also  appears  to  be  essential  to  the  exercise  of  the  higher  functions  of  the 
animal,  since  it  exists  as  a  never-failing  ingredient  in  the  substance  of  which 
the  brain  and  nerves  are  composed." 

400.  P  r  e  p  a  r  a  t  i  o  n. — Phosphorus  was  formerly  extracted  from  urine, 
but  at  the  present  time  it  is  obtained  almost  exclusively  from  bones,  from 
which  immense  quantities  are  prepared  for  the  manufacture  of  matches  and 
other  usea 

The  details  of  the  process  of  preparation  are  briefly  as  follows : — The  bones 
are  first  burned  to  whiteness  and  then  reduced  to  a  fine  powder,  which  pow- 
der, being  a  phosphate  of  lime,  insoluble  hi  water,  is  technically  known  in 
chemistry  and  the  arts  as  "bone-ash."  So  much  sulphuric  acid  and  water 
is  then  added  to  a  suitable  quantity  of  bone-ash  as  will,  in  the  course  of  a 
few  days,  partially  decompose  it — two  thirds  of  the  lime  uniting  with  the 
sulphuric  acid  to  form  an  insoluble  sulphate  of  lime,  while  the  remaining  one 
third  continues  in  combination  with  the  whole  of  the  phosphoric  acid  to  form 
a  new  compound,  which  is  readily  soluble  in  water.  This  new  compound  is 
called  superphosphate  of  lime,  and  of  late  years  has  been  extensively  intro- 
duced into  agriculture,  as  a  ready  means  of  supplying  exhausted  soils  with 
the  phosphorus  needed  for  the  production  of  crops.  The  chemical  reaction 
which  takes  place  may  be  expressed  in  symbols  as  follows : — 

Bone-ash.  Sulph.  acid.  Superphosph.  lime.  Sulph.  lime. 

3CaO,P05  -j-  2(S03,HO)  —  2HO,CaO,P05  +  2(CaO,S03) 

The  insoluble  sulphate  of  lime  and  the  superphosphate  of  lime  dissolved  in 
the  acid  solution,  are  then  separated  from  each  other  by  filtration,  and  the 
latter,  evaporated  to  a  syrup,  is  mixed  with  charcoal,  and  heated  in  an  iron, 
or  earthen  retort.  Under  these  circumstances  the  charcoal  decomposes  the 
superphosphate  of  lime ; — phosphorus  rises  as  a  vapor,  and  passing  into  cold 
water,  is  collected  and  condensed  into  a  solid.  The  crude  phosphorus  thus 
obtained  is  purified  by  melting  under  water,  and  is  then  cast  into  sticks,  in 
which  form  it  is  sold. 

401.  Properties  . — Phosphorus  exists  in  two  conditions,  viz. :  in  an 
ordinary  state,  and  in  an  allotropic  state.    In  its  ordinary  state  it  is  a  soft,  semi- 
transparent,  almost  colorless,  waxy -look  ing  solid.     It  is  insoluble  in  water, 
but  readily  soluble  in  ether,  alcohol,  and  in  various  oils. 

At  all  temperatures  above  32°  F.,  phosphorus,  when  exposed  to  the  air, 
slowly  combines  with  oxygen,  and  emits  a  feeble  light,  readily  perceptible  in 
the  dark  (hence  its  name,  from  0o>f ,  light,  and  <j>epeiv,  to  bear).  Exposed  to  a 
temperature  of  about  60°  F.  it  bursts  into  a  flame.  This  extreme  combusti- 
bility of  phosphorus  renders  it  necessary  to  keep  it  continually  under  water, 
from  which  it  should  be  taken,  for  the  purpose  of  experiment,  with  great  cau- 
tion, and  be  held  with  a  pair  of  forceps,  or  upon  the  point  of  a  knife.  When- 

QUESTIONS.— How  is  phosphorus  obtained  ?  What  is  superphosphate  of  lime  ?  What 
is  the  chemical  reaction  involved  in  its  manufacture  ?  What  are  the  properties  of  ordinary 
phosphorus  ?  What  is  said  of  its  solubility  ?  What  of  its  inflammability  ? 


PHOSPHORUS.  271 

ever,  also,  it  is  desirable  to  cut  it  into  fragments,  the  operation  should  be  per- 
formed under  water.  The  burns  occasioned  by  melted  phosphorus  are 
extremely  severe,  from  the  difficulty  of  extinguishing  the  flame. 

Phosphorus  is  also  easily  ignited  by  friction,  and  for  this  reason  is  em- 
ployed in  the  manufacture  of  matches.  It  burns  in  the  air  with  a  brilliant 
flame,  and  in  pure  oxygen  gas  with  a  light  so  dazzling  that  the  eye  can  hardly 
sustain  it.  (§  282.) 

At  a  temperature  of  111°  F.,  air  being  excluded,  phosphorus  melts;  and 
when  fused  under  water,  it  can  be  molded  as  readily  as  wax.  At  550°  F., 
in  close  vessels,  it  boils,  giving  off  a  colorless  gas.  A  solution  of  phosphorus 
in  naphtha,  by  cooling  and  evaporation,  yields  crystals  of  phosphorus.  Very 
fine  crystals  of  phosphorus  may  be  also  obtained  by  exposing  phosphorus  to 
sunlight  in  a  tube  either  exhausted  of  air,  or  filled  with  a  gas  which  can  not 
oxydize  it 

The  following  experiments  illustrate  some  of  the  characteristics  of  this 
element: — 

Place  in  a  glass  flask  about  a  quarter  of  an  ounce  of  ether  and  a  piece  of 
phosphorus  of  the  size  of  a  pea.  Cork  the  flask  and  allow  it  to  stand  some 
days,  frequently  agitating  it.  In  this  way  an  ethereal  solution  of  phosphorus 
will  be  obtained,  which,  when  rubbed  upon  the  hands,  renders  them  luminous 
in  the  dark.  The  explanation  of  this  phenomenon  is,  that  the  ether  evapo- 
rates, and  leaves  the  phosphorus  which  it  held  in  solution  upon  the  hands  in 
a  state  of  minute  subdivision.  In  this  condition  it  combines  with  the  oxygen 
of  the  ah-,  or  undergoes  a  slow  combustion,  diffusing  a  white  smoke  and  a 
pale  greenish  light.  Heat  is  at  the  same  time  evolved,  but  not  sufficient  to 
occasion  ignition.  By  rubbing  the  hands,  the  light  is  rendered  more  vivid, 
as  a  fresh  surface  of  phosphorus  is  thus  continually  presented  to  the  oxygen 
of  the  air. 

If  we  moisten  a  lump  of  white  sugar  with  an  ethereal  solution  of  phos- 
phorus, and  throw  it  into  hot  water,  the  heat  of  the  water  will  volatilize  both 
the  ether  and  the  phosphorus ;  and  the  vapors,  in  rising  to  the  surface  of  the 
water,  and  coming  in  contact  with  the  oxygen  of  the  air,  will  inflame  spon- 
taneously. 

If  we  pour  an  ethereal  solution  of  phosphorus  upon  fine  blotting-paper,  the 
latter  will  ignite  spontaneously  after  the  ether  has  evaporated. 

If  we  place  a  piece  of  phosphorus  of  the  size  of  a  pea  upon  blotting-paper, 
and  sprinkle  over  it  some  soot  or  finely-pulverized  charcoal,  the  phosphorus, 
after  a  little  time,  melts,  and  at  length  spontaneously  inflames.  The  finely- 
pulverized  charcoal  causes  this  combustion,  owing  to  its  porosity,  which  en- 
ables it  to  readily  absorb  oxygen  from  the  air.  This  oxygen  is  in  turn  im- 
parted to  the  phosphorus,  and  by  uniting  with  it,  occasions  heat,  which, 
prevented  by  the  non-conducting  properties  of  the  charcoal  from  escaping, 
accumulates,  and  occasions  combustion. 

QUESTIONS. — "What  property  renders  phosphorus  available  for  the  manufacture  of 
matches  ?  What  experiments  illustrate  the  characteristics  of  phosphorus  ? 


272  INORGANIC     CHEMISTRY. 

Phosphorus  when  taken  internally  is  a  most  violent  poison,  and  in  combin- 
ation with  other  substances,  is.  frequently  used  for  the  destruction  of  rats  and 
vermin.  The  so-called  rat-exterminating  poison  is  composed  of  1  dram  of 
phosphorus,  8  ounces  of  hot  water,  and  3  ounces  of  flour. 

402.  Allot  ropic   or  Amorphous   Phosphorus  , — It  has  long 
been  noticed,  when  phosphorus  is  exposed  to  the  action  of  light  for  a  consid- 
erable length  of  time,  that  its-  exterior  becomes  coated  with  a  red  powder,  and 
that  the  same  product  is  formed  when  phosphorus  is  burned!  with  a  limited 
supply  of  air.    This  red  powder  was  always  supposed  to  be  an  oxyd  of  phos- 
phorusT  but  within  a  recent  period,  Prof.  Schrotter  of  Vienna  has  succeeded 
in  demonstrating  that  the  substance  in  question  is  merely  an  allotropic  state 
of  ordinary  phosphorus.     He  has  shown  that  if  ordinary  phosphorus  be  sub- 
mitted to  the  action  of  a  prolonged  heatr  within;  certain  limitsr  and  under 
circumstances  involving;  an  entire-  exclusion  of  oxygen,  it  becomes  converted 
into  a  brick-red  substance; — "not  soluble  in  any  of  the  ordinary  solvents  of 
phosphorus — not  igniting  by  ordinary  friction — not  luminous  at  ordinary  tem- 
peratures— not  poisonous ;  distinguished,,  in  fact,  for  negative  properties,  as 
common  phosphorus  is  for  active  ones  \  and  yet  this  wonderful  change  is  only 
molecular ;  that  is,  the  phosphorus  is  not  converted  into  a  compound :  it  has 
combined  with  nothing,  it  has  lost  nothing,  but  its  particles  have  probably 
arranged  themselves  with  respect  to  each  other,  in  a  manner  different  front 
that  of  the  particles  of  common  phosphorus."    Common  phosphorus  we  are 
obliged  to  keep  in  water,  for  the  purpose  of  guarding  against  spontaneous 
combustion  •  allotropic  phosphorus,  however,  may  be  kept  unchanged  in  at- 
mospheric air,  and  may  be  handled  or  even  carried  in  the  pocket  with  im- 
punity.    Exposed  to  a  temperature  of  about  480°  F.,  it  melts,  and  returns  to 
the  condition  of  ordinary  phosphorus ;  and  at  a  temperature  of  500°  it  bursts 
into  flame  with  a  sort  of  explosion.    The  identity  of  the  two  substances  is 
proved  by  their  ready  conversion  into  each  other,,  and  by  the  fact  that  the 
compounds  which  they  form  with  other  bodies  are  the  same. 

403,  Matches  . — Some  notice  of  the  history  and  manufacture  of  matches 
is  appropriate  in  connection  with  the  subject  of  phosphorus. 

The  comparatively  low  temperature  at  which  sulphur  ignites,  early  sug- 
gested its  application  to  the  end  of  a  strip  of  dry  wood,  as  a  means  of  procur- 
ing flame.  The  old  sulphur  match  was  chiefly  used  in  connection  with  a  flint 
and  steel,  and  a  box  for  holding  tinder.  The  tinder,  formed  by  the  partial 
combustion  of  a  linen  or  cotton  rag,  was  first  ignited  by  means  of  a  spark 
resulting  from  a  collision  of  a  flint  and  steel,  and  this  in  turn  communicated 
the  fire  to  the  match.  Fifty  years  ago,  a  "tinder-box"  was  as  much  an  indis- 
pensable article  of  household  economy  as  a  paper  of  matches  is  at  the  present 
clay. 

Soon  after  the  discovery  of  phosphorus,  attempts  were  made  to  use  it  as  a 

QUESTIONS. — What  is  said  of  the  poisonous  properties  of  phosphorus?  What  is  rat- 
poison  ?  What  is  said  of  allotropic  phosphorus  ?  In  trhat  respects  does  allotropic  differ 
from  ordinary  phosphorus  ?  How  can  we  prove  that  allotropic  and  common  phosphorus 
are  the  same  ?  What  is  said  of  the  history  and  origin  of  matches  ? 


PHOSPHORUS. 

method  of  procuring  fire,  but  its  costliness  prevented  its  general  introduction 
and  use  for  this  purpose,  for  nearly  one  hundred  and  fifty  years.  One  of  the 
first  methods  of  applying  it  was  to  put  a  piece  of  phosphorus  in  a  phial,  and 
then  to  stir  it  with  a  hot  iron  wire ;  the  phosphorus  was  partially  burnt  in  the 
confined  portion  of  air,  and  the  interior  of  the  bottle  became  covered  with  an 
oxyd  of  phosphorus  |  on  removing  the  wire,  the  phial  was  corked  tightly  for 
use,  When  a  light  was  wanted,  a  common  sulphur  match  was  dipped  into 
the  bottle,  and  a  small  portion  of  the  phosphorus  adhering  to  the  tip,  flame 
\vas  produced  by  the  energetic  chemical  action  of  the  sulphur  and  the  phos- 
phorus. Various  other  inventions  were  employed  for  procuring  fire ; — such 
as  the  sudden  condensing  of  air  in  a  syringe  furnished  with  a  piston  and  an 
arrangement  for  holding  tinder— apparatus  for  igniting  tinder  by  an  electric 
spark^-Dobereiner's  Lamp  (§  297),  etc.,  etc,  In  fact,  during  the  whole  of  the 
last  century,  and  even  later,  the  invention  of  a  safe,  convenient,  and  reliable 
agent  for  kindling  a  fire  or  light,  was  regarded  as  one  of  the  great  wants  of 
the  age, 

The  next  important  step  taken  in  perfecting  the  match,  was  the  employ- 
ment of  chlorate  of  potash.  The  match  stick  was  tipped  with  a  mixture 
of  chlorate  of  potash  and  sugar,  and  ignited  by  immersion  in  a  little  bot- 
tle containing  asbestos  soaked  in  sulphuric  acid.  (For  explanation  of  this 
phenomenon  see  §  368.)  Matches  thus  prepared  were  put  up  in  cases,  which 
contained  in  one  compartment  a  small  bottle  of  acid,  Their  price,  when  first 
introduced,  was  $4  75  for  a  case  of  100;  but  subsequently  was  reduced  to 
50  .cents.  These  matches  continued  in  use  Until  within  a  Very  recent  period, 

The  next  important  invention  was  that  of  the  so-called  "  Lucifer  Matches," 
which  Were  tipped  with  a  paste  of  chlorate  of  potash  and  sulphuret  of  anti- 
mony mixed  with  starch,  and  were  ignited  by  drawing  the  match  between 
two  surfaces  of  sand-paper.  These  were  the  first  friction  matches.  In  1834, 
phosphorus  was  substituted  in  the  place  of  antimony,  and  the  match  was  ig- 
nited by  friction  Upon  any  rough  surface.  Subsequently,  saltpeter  was  sub- 
stituted in  the  place  of  chlorate  of  potash,  which  produced  quiet  ignition  in- 
stead of  detonation. 

The  details  of  the  manufacture  of  matches  at  the  present  time  are  generally 
as  follows ;  The  ends  of  the  wooden  match-splints,  which  are  sawed  by  ma- 
chinery, are  first  sulphured,  by  immersion  in  a  pot  of  melted  sulphur,  When 
dried,  they  are  next  dipped  in  the  phosphorus  composition,  which  is  a  paste 
prepared  by  mixing  together  in  a  hot  solution  of  glue,  or  gum,  in  water,  phos- 
phorus, saltpeter,  and  generally  red-lead  and  some  coloring  ingredients ; — if 
the  tips  of  the  matches  are  to  be  red,  vermillion  is  added ;  or  if  blue,  Prus- 
sian blue. 

The  various  reactions  which  take  place  when  a  match  is  fired  are  as  follows: 
the  phosphorus  contained  in  the  composition  is  first  ignited  by  the  heat 

QUESTIONS.— What  were  some  of  the  early  methods  resorted  to  fitf  the  purpose  of  ob- 
taining a  light  ?  When  Was  phosphorus  first  applied  to  the  manufacture  of  matches  ? 
What  were  the  first  friction  matched?  How  ar>,  matches  manufactured?  What  chem- 
ical reactions  are  involved  in  the  firing  of  a  match  ? 

12* 


274  INOBGANIC     CHEMISTRY. 

evolved  by  friction  or  compression;  and  the  heat  occasioned  by  its  combustion 
decomposes  the  saltpeter  and  the  red-lead ;  the  se  substances,  in  their  decom- 
position, evolve  oxygen,  which  supports  the  flame,  adds  to  its  heat,  and  en- 
ables it  to  ignite  the  sulphur,  which  in  turn  inflames  the  wood.  The  odor  of 
a  burning  match  is  occasioned  by  the  combustion  of  the  sulphur,  and  in  some 
recent  inventions,  has  been  obviated  by  the  substitution  of  stearine  in  the 
place  of  sulphur.  The  temperature  required  for  kindling  matches  varies  from 
150  to  160°  F.* 

The  manufacture  of  matches  is  attended  with  danger,  not  only  from  the 
highly  inflammable  nature  of  the  ingredients  used,  but  also  from  the  fact,  that 
a  continued  exposure  to  the  vapor  of  phosphorus,  produces  a  disorganization 
of  the  jaw-bones,  causing  excruciating  suffering,  and  usually  terminating  in 
death.  The  phosphorus,  in  the  first  instance,  attacks  a  little  spot  of  decay 
upon  a  tooth,  and  from  this  ulceration  spreads  with  great  rapidity.  Of  these 
evils  the  first  is  greatly  lessened,  and  the  second  altogether  avoided,  by  the 
use  of  the  amorphous  or  allotropic  phosphorus,  before  described. 

404.  Compounds  of  Phosphorus  with  Oxygen,  —  Phos- 
phorus unites  with  oxygen  to  form  four  compounds,  viz.  :— 

Composed  by  weight  ot 

Phosphoric  acid POs  32  phosphorus  40  oxygen. 

Phosphorus  acid POs  32  "  24        " 

Hypophosphorusacid..*. PO  32  8        u 

Oxyd  of  Phosphorus PaO  64  "  8        " 

405.  Phosphoric  Acid,  PO5. — This  acid,  which  is  the 
most  important  of  the  oxyds  of  phosphorus,  is  the  sole 
product  of  the  rapid  combustion  of  phosphorus  in  oxygen, 
or  atmospheric  air. 

It  appears  as  a  dense  white  vapor,  which  condenses  on  cooling  into  a  white 
powder.  It  may  be  easily  collected  by  burning  phosphorus  in  air  under  a 
dry  bell  glass.  As  thus  prepared,  it  has  so  great  an  avidity  for  water,  that 
when  brought  in  contact  with  it,  it  hisses  like  a  hot  iron.  Exposed  to  the 
air  for  a  few  moments,  it  absorbs  moisture,  and  deliquesces  to  a  liquid.  When 
once  converted  into  a  hydrate,  water  can  not  be  entirely  separated  from  it. 
Its  solution  is  intensely  acid,  and  when  evaporated  to  dryness,  yields,  on  cool- 
ing, a  glassy,  transparent  solid,  known  as  glacial  plwsplwric  acid. 

Phosphoric  acid  may  also  be  prepared  by  the  action  of  nitric  acid  on  phos- 
phorus, and  also  from  bones,  by  the  action  of  sulphuric  acid.  It  combines 

*  Some  idea  of  the  importance  of  the  manufacture  of  matches  as  a  branch  of  industrial 
art,  may  be  formed  from  the  following  statistics  of  materials  consumed  in  Austria  in  one 
year,  1849,  for  this  purpose— 125,000  Ibs.  of  saltpeter,  32,500  Ibs.  of  phosphorus,  1,500,000 
Ibs.  of  sulphur. 

QirESTioNa— What  is  the  temperature  required  for  kindling  a  match  ?  What  effect  has 
the  vapor  of  phosphorus  upon  the  animal  system  ?  What  compounds  does  phosphorus 
form  with  oxygen  ?  How  is  phosphoric  acid  prepared  ?  What  are  its  properties  ? 


PHOSPHORUS.  275 

with  water  in  three  proportions,  to  form  three  distinct  hydrates,  which  unite 
with  bases  to  form  three  classes  of  salts.  The  nomenclature  and  composition 
of  these  hydrates,  which  are  of  great  scientific  interest,  may  be  represented  as 

follows : — 

Acids. 

Monobasic  or  metaphosphoric  acid HO.POs, 

Bibasic  or  pyrophosphoric  acid 2HO.P05, 

Tribasic  or  common  phosphorus  acid SHO.POs. 

It  is  in  the  form  of  phosphoric  acid,  united  with  some  base,  generally  lima 
or  magnesia,  that  phosphorus  exists  in  the  bones,  in  the  seeds  and  tissues  of 
plants,  and  in  the  soil. 

406.  Phosphorus   Acid,  P  03  is  the  principal  product  which  results 
from  the  slow  combustion  which  occurs  when  phosphorus  is  exposed  to  the 
oxygen  of  the  atmosphere.     It  may  also  be  formed  by  burning  phosphorus 
with  a  limited  supply  of  air. 

The  other  oxyds  of  phosphorus  are  comparatively  unimportant. 

407.  Phosphorus    and    Hydrogen , — P  hosphuretted    Hy- 
drogen,   P  H3. — Phosphorus  unites  with  hydrogen  in  three  proportions  to 
form  three  compounds;  one  of  which,  a  gas,  phosphuretted  hydrogen,  pos- 
sesses the  property,  under  certain  circumstances,  of  inflaming  spontaneously 
on  exposure  to  air,  or  oxygen  gas. 

This  substance  is  conveniently  prepared  by  heating  fragments  of  phosphorus  in 
a  retort,  with  a  strong  solution  of  caustic  potash,  or  cream  of  lime,  prepared  from 
lime  recently  slacked.*  On  the  j?IG.  132. 

application  of  a  gentle  heat  to 
the  retort,  the  beak  of  which  is 
caused  to  dip  slightly  beneath 
the  surface  of  water,  the  gas  is 
evolved,  and  the  bubbles,  as 
they  rise  and  come  in  contact 
with  the  air,  spontaneously  in- 
flame. (See  Fig.  132.)  Each 
bubble,  as  it  breaks  and  ignites, 

FIG.  133.  produces  a  beautiful  white  wreath  of  smoke  (vapor 

°f  phosphoric  acid),  composed  of  a  number  of  concen- 
trie  rings,  revolving  around  the  axis  of  the  wreath,  as 
!t  ascends  (see  FiS-  133);  thus  tracing  before  the  eye, 
with  perfect  distinctness,  the  peculiar  gyratory  movo- 

*  la  this  experiment  it  is  best  to  employ  a  very  small  flask  or  retort,  and  in  order  to 
avoid  the  presence  of  atmospheric  air,  it  is  advisable  to  fill  it  full  to  the  neck  with  tha 
cream  of  lime,  or  potash  solution.  For  an  ounce  flask,  a  piece  of  phosphorus  of  the  size 
of  a  pea  is  sufficient.  It  is  best,  also,  not  to  apply  heat  to  the  glass  directly,  but  to  place 
it  in  a  basin  containing  a  solution  of  salt,  which  is  then  heated  to  a  boiling  temperature 
by  a  spirit  lamp. 

QUESTIONS. — What  is  said  of  its  combinations  with  water  ?  In  what  state  does  phosphorus 
generally  exist  in  nature  ?  "What  is  said  of  phosphorus  acid  ?  "What  is  said  of  phosphuret- 
ted hydrogen  ?  How  is  it  prepared  f  What  phenomenon  attends  its  evolution  in  air  ? 


276  INORGANIC    CHEMISTRY. 

FiG,  134.  merits  imparted  to  air  by  the  impulse  of  a  force  acting 
suddenly  upon  a  mass  of  air  in  all  directions,  from  a 
center.  The  same  phenomen  is  also  seen  in  the  rays  of 
smoke  produced  by  the  mouth  of  a  skillful  tobacco- 
gmoker,  and  frequently  also,  upon  a  much  larger  scale, 
during  the  discharge  of  cannon  on  a  still  day. 

Phosphuretted  hydrogen  may  be  more  simply  pre- 
pared by  throwing  into  a  glass  of  water  a  few  pieces  of 
phosphuret  of  calcium.  This  substance,  by  contact  with 
the  water,  is  decomposed,  and  evolves  the  spontaneously 
inflammable  gas.  (See  Fig.  134.) 

408.  Properties . — Phosphuretted  hydrogen  is  a 
colorless,  transparent  gas,  possessing  an  offensive,  foetid  odor,  and  producing 
a  poisonous  action  upon  the  system,  when  inhaled.  It  loses  its  spontaneous 
-inflammability  by  standing  for  a  time  over  water,  and  also  by  the  addition  of 
the  vapor  of  some  inflammable  bodies,  such  as  ether,  oil  of  turpentine,  etc.  By 
varying  the  conditions  of  its  preparation,  it  may  also  be  evolved  without  the 
self-lighting  power. 

The  production  of  this  gas,  by  the  decay  of  bones  and  other  organic  pro- 
ducts in  wet,  swampy  places,  and  its  subsequent  ignition  in  contact  with  the 
air,  is  supposed  to  have  originated  the  popular  superstition  known  as  the 
"Ignis  Fatuus,"  or  "  Will-o'-the-wisp.1'* 

SECTION    XII. 

BOEON. 
Equivalent,  10'9.     Symbol,  B. 

409.  History  and  Distribution, — Boron  is  an  element 
that  is  always  found  in  nature  in  composition  with  oxygen, 
forming  boracic  acid.  The  latter  substance  is  found  only 
in  few  localities,  and  in  comparatively  small  quantities. 
United  with  soda  it  forms  a  salt,  borax,  which  is  a  well- 
known  article  of  commerce. 

Until  within  a  very  recent  period  (185G-7),  comparatively  little  has  been 
known  respecting  the  nature  of  the  pure  element,  boron.  It  has  been  recently 
ascertained,  however,  that  it  is  closely  allied  to  carbon,  and  that  it  exists  in 

•  It  is  generally  taken  for  granted  that  luminous  appearances  in  the  air  are  often  seen 
in  the  vicinity  of  swamps,  grare-yards,  or  other  receptacles  of  decaying  organic  matter, 
Suchr  however,  is  not  the  fact ;  and  it  is  extremely  doubtful  whether  any  well  authenti- 
cated instance  of  such  an  appearance  can  be  cited.  The  generally-received  account  of  the 
"  Ignis  fatuus"  must  therefore  be  regarded  as  a  fiction. 

QUESTIONS. — What  are  the  properties  of  phosphuretted  hydrogen  ?  What  popular  su- 
perstition is  it  supposed  to  have  originated  ?  What  is  said  of  boron  ? 


BORON.  277 

three  allotropic  conditions,  viz.,  as  a  chocolate-brown  amorphous  substance  ; 
as  an  opaque,  semi  crystalline  body,  occurring  in  thin  plates,  with  a  black- 
lead  luster ;  and,  lastly,  in  a  crystalline  condition,  resembling  the  diamond  in 
luster,  hardness,  and  refractive  power.  As  yet,  chemists  have  been  only  able 
to  obtain  it  in  very  minute  crystals ;  but  if  larger  crystals  can  be  prepared,  it 
will  undoubtedly  take  rank  as  one  of  the  most  valuable  of  gems.  Its  method 
of  preparation  consists  essentially  in  fusing  boracic  acid  with  the  metal  alum- 
inum. 

410.  Boracic  Acid,  B03  is  found  in  small  quantities  in  Thibet  and 
in  South  America,  but  the  principal  supply  is  from  volcanic  districts  of  Tus- 
cany, in  Italy,  called  lagoons,  where  jets  of  vapor  and  of  boiling  water,  charged 
with  boracic  acid,  are  continually  issuing  from  fissures  in  the  earth.* 

The  manner  in  which  the  boracic  acid  is  collected  is  as  follows :  A  locality 
is  chosen,  where  the  soil  is  observed  to  possess  a  high  temperature,  and  a 
basin  of  moderate  depth  (A,  Fig.  135)  is  excavated,  and  walled  up  with 

FIG.  135. 


a  masonry — openings,  v,  being  left  in  the  bottom  for  the  admission  of  the 
steam  escaping  from  the  earth.f  "Water  from  adjacent  springs  is  then  con- 
ducted into  the  basin,  which  absorbs  the  boracic  acid  brought  tip  by  the  as- 
cending vapor,  and  at  the  same  time  becomes  heated  to  the  boiling  tempera- 
ture. After  the  lapse  of  twenty-four  hours,  the  solution  is  drawn  off  into  a 
similar- constructed  basin,  B,  at  a  lower  level,  and  from  thence  a  third,  C,  and 


*  "  As  you  approach  the  lagoons,  the  earth  seems  to  pour  out  boiling-water,  as  if  from 
volcanoes  of  various  sizes,  in  a  variety  of  soils,  but  chiefly  of  chalk  and  sand.  The  heat 
in  the  immediate  neighborhood  is  intolerable,  and  you  are  drenched  with  Vapor,  which 
impregnates  the  atmosphere  with  a  strong  and  somewhat  salphuroBs  SmelL  The  whole 
scene  is  one  of  terrible  violence  and  confusion  i— the  noisy  outbreak  of  the  boiling  water ; 
the  rugged  and  blasted  surface ;  the  volumes  of  vapor  ;  the  impregnated  atmosphere. 
The  ground  burns  and  shakes  beneath  your  feet,  and  the  whole  surface  is  covered  with 
beautiful  crystallizations  of  ealphor  and  other  minerals." — DR.  BOWRING. 

t  The  dimensions  of  these  basins  vary  from  100  feet  in  circumference  and  7  feet  deep, 
to  500  and  1000  feet  in  circumference  and  15  to  20  feet  deep. 

QUESTIONS. — What  are  its  properties  ?  What  is  said  of  boracic  acid  ?  How  is  it  col. 
lected  ? 


278  INORGANIC     CHEMISTRY. 

so  on,  until  the  water,  having  absorbed  the  greatest  possible  amount  of  bor- 
acic  acid,  is  transferred  into  shallow  tanks,  E,  for  purification.  The  solution 
thus  obtained  is  evaporated  in  leaden  pans  heated  by  the  volcanic  steam, 
until  the  boracic  acid  contained  in  it  is  deposited  in  white,  scaley  crystals. 
The  annual  production  of  boracic  acid  from  these  sources  is  at  present  about 
three  million  pounds. 

Boracic  acid  has  a  white,  pearly  luster  and  a  greasy  feeling.  It  is  a  feeble 
acid,  sparingly  soluble  in  cold  water,  but  dissolving  in  three  times  its  weight 
of  boiling  water.  Its  solution  in  alcohol  burns  with  a  beautiful  green  flame, 
which  constitutes  a  test  of  the  presence  of  boron.  This  property  may  bo 
illustrated  by  igniting  a  solution  of  borax  in  alcohol  in  a  shallow  cup,  and 
stirring  the  liquid  with  a  glass  rod  while  burning. 

411.  Borax,  or  Biborate  of  Soda,  is  formed  by  adding  car- 
bonate of  soda  to  a  solution  of  boracic  acid.  This  salt  is  composed  of  two 
equivalents  of  acid,  one  of  base,  and  ten  of  water  —  its  constitution  being  rep- 
resented as  follows,  NaO,  2BO-J-10  HO.  Borax  is  obtained  naturally  in 
small  quantities  and  in  an  impure  state,  by  the  evaporation  of  the  waters  of 
certain  lakes  in  Thibet,  and  is  exported  under  the  name  of  tincaL 

Borax  is  chiefly  used  in  the  arts  as  a  flux  in  the  welding,  soldering,  and 
refining  of  metals. 

The  term  flux  is  applied  in  metallurgy  to  those  sub- 
stances which  assist  fusion,  either  by  expediting  the  pro- 
cess, or  by  protecting  the  substance  melted  from  oxyda- 
tion. 

Borax,  when  heated,  bubbles  up,  loses  its  water  of  crystallization,  and  at  a 
temperature  below  red-heat,  melts  into  a  transparent  glass.  The  property 
which  this  glass  possesses  of  dissolving  the  metallic  oxyds,  gives  to  borax  its 
value  as  a  flux.  For  example  :  in  the  welding  of  iron,  a  union  between  two 
surfaces  can  not  be  effected  unless  both  are  clean  and  perfectly  free  from  ox- 
ydation  ;  but  a  piece  of  iron  can  not  be  strongly  heated  without  the  formation 
of  a  layer  of  oxyd  upon  its  surface.  This  difficulty  is  obviated  by  sprinkling 
the  hot  surfaces  with  powdered  borax,  which,  as  it  melts,  not  only  dissolves 
off  the  oxyd,  or  scale  already  present,  but  keeps  the  metal  bright  by  prevent- 
ing all  further  oxydation. 

Borax  is  also  much  used  as  a  test  before  the  blow-pipe,  for  recognizing  the 
presence  of  certain  metallic  oxyds.  For  this  purpose,  a  small  crystal  of  borax 
is  fused  upon  the  end  of  a  bent  platinum  wire,  and  a  minute  quantity  of  tho 
substance  to  be  tested  is  melted  with  the  salt  in  the  flame  of  the  blow-pipe. 
The  peculiar  color  which  the  borax  glass  receives,  indicates  the  character  of 
the  coloring  substance  :  thus,  with  an  oxyd  of  chromium,  the  borax  forms  an 
emerald-green  glass  ;  with  oxyd  of  cobalt,  a  blue  ;  with  manganese,  a  violet  ; 
with  iron,  a  yellow,  and  so  on. 


g.  —  Wlistt  Jii'o  the  properties  of  boracic  acid?  What  is  borax?  For  what  pur- 
pose is  it  UKed  in  the  arts?  Whsit  is  a  flux?  What  gives  to  borax  its  value  as  a  flux? 
Illustrate  this.  How  does  borax  serve  as  a  blow-pipe  reagent  ? 


SILICON.  279 

SECTION   XIII. 

SILICON,     or     SILICIUM. 
Equivalent,  21*2.     Symbol,  Si. 

412.  Distribution, — Silicon,  in  combination  with  oxy- 
gen,  is  the  most   abundant  of  all  the   solid  substances 
which  compose  the  crust  of  our  globe.     All  rocks  which 
are  not  calcareous  (lime)  are  silicious. 

.  It  is  only  within  a  very  recent  period  (1855-7)  that  chemists  have  been  en- 
abled to  obtain  any  very  definite  knowledge  respecting  the  nature  and  prop- 
erties of  pure  silicon.  It  is  now  known  to  exist,  like  carbon  and  boron,  in 
three  allotropic  conditions ;  in  an  amorphous  nut-brown  powder ;  in  a  condi- 
tion resembling  graphite  (black-lead) ;  and  in  a  crystalline  condition.-  It  has 
most  of  the  characteristics  of  the  metals,  and  by  the  most  recent  authorities  is 
classed  with  them.  As  prepared  by  a  somewhat  complicated  process,  it  is 
easily  fusible,  and  may  be  run  into  ingots  and  alloyed  with  copper  and  iron. 
At  a  meeting  of  the  French  Academy  in  1857,  two  small  cannon  composed 
of  an  alloy  of  copper  and  silicon  were  exhibited. 

413.  Silicic  Acid,  or  Silica,  SiOs,  is  the  principal  oxyd 
of  silicon,  and  the  most  important  of  all  its  compounds. 
In  fact,  it  is  in  this  condition  only  that  silicon  is  found  in 
nature. 

When  pure,  or  merely  colored  by  small  quantities  of  different  oxyds,  it  is 
very  generally  termed  quartz.     It  is  frequently  found  crystallized,  its  ordinary 
form  being  a  six-sided  prism,  terminated  by  six-sided  pyra-        fiQ.  136. 
mids,   as  in  rock-crystal.     (See  Fig.    136.)     Sometimes  the 
prism  is  very  short  and  disappear  entirely,  and  the  pyramid 
only  is  seen,  as  in  common  quartz.     In  transparent  and  col- 
orless rock-crystal,  silica  is  almost  absolutely  pure,  and  in  this 
condition  is  not  unfrequently  used  in  jewelry.     Amethyst  is 
crystallized  quartz,  colored  purple  by  the  presence  of  protoxyd 
of  manganese.     Common  flint,  agate,  carnelian,  chalcedony, 
jasper,  and  opal,  are  other  varieties  of  nearly  pure  silica, 
I  heir  colors  being  occasioned  by  the  presence  of  different  me- 
tallic oxyds.     Common  sand  is  mainly  composed  of  silica, 
colored  yellow  or  brown  by  the  presence  of  oxyd  of  iron  ;  sand  cemented  into 
rock-masses,  through  the  agency  mainly  of  silica,  is  termed  "  sandstone." 

Many  plants  absorb  silica  from  the  soil  in  considerable  quantity,  and  deposit 

QUESTIONS.— What  is  the  natural  history  of  silicon  ?  What  is  known  respecting  the 
pure  element?  What  is  silica  ?  "What  is  quartz?  In  what  minerals  does  silica  nearly 
pure  exist  ?  What  is  amethyst  ?  To  what  are  the  colors  of  agate,  chalcedony,  opal,  etc., 
due  ?  What  is  common  sand  ?  What  is  sandstone  ?  Does  silica  exist  in  plants? 


280  INORGANIC    CHEMISTHY, 

it  upon  the  exterior  of  their  stalks,  or  stems,  Examples  of  this  may  be  seen 
in  the  glossy  coating  which  invests  the  outside  of  straw,  cane,  rattan,  bam- 
boo, etc.  In  these  instances,  the  silica  subserves  the  same  purpose  in  the 
structure  of  the  plant  that  bones  do  in  the  structure  of  men  and  animals-— 
that  is,  it  gives  to  the  stalk  firmness  and  stiffness.  The  straw  of  wheat  grown 
upon  soils  deficient  in  "  soluble  silica,"  is  so  weak  as  to  be  hardly  capable 
of  supporting  the  weight  of  the  seed. 

In  the  animal  kingdom,  silica  exists  in  the  feathers  and  hair  of  animals, 
and  recent  researches  have  also  detected  it  in  the  blood. 

414.  Properties  .—-Pure  silica  is  not  affected  by  the  heat  of  the  strong- 
est wind  furnace,  but  before  the  flame  of  the  oxyhydrogen  blow-pipe  it  melts 
into  a  transparent  glass.  In  its  native  state  it  is  insoluble  in  pure  water,  and 
in  all  acids  except  hydrofluoric.  In  hardness  it  approaches  the  precious  gems, 
and  it  scratches  glass  easily. 

Silica,  although  it  presents  the  characters  of  an  earth,  is  in  reality  an  acid, 
and  a  most  powerful  one.  Under  all  ordinary  circumstances,  however,  its 
acid  properties  are  not  manifested  by  reason  of  its  almost  entire  insolubility. 

When  silica  is  digested  in  solutions  of  the  alkalies  it  gradually  unites  with 
them,  and  forms  salts—silicates  of  potash  or  soda— which  are  readily  soluble. 
Even  flints  in  their  unground  condition,  or  fragments  of  quartz  when  placed 
in  strong  solutions  of  caustic  potash  or  soda,  at  a  high  temperature,  are  readily 
caused  to  pass  into  solution.  When  solutions  of  silica  in  an  excess  of  alkali 
are  concentrated,  a  semi-fluid  mass  closely  resembling  a  solution  of  starch  is 
produced.  This  product  is  known  as  soluble  glass,  and  is  readily  Soluble  in  hot 
water,  and  can  be  applied  as  a  varnish  for  rendering;  surfaces  of  wood  or  cloth 
fire-proof.  It  has  also  been  used  to  some  extent  a.s  a  substitute  for  starch  or 
gum  in  the  stiffening  of  fibrous  substances.  Ancient  monuments  or  buildings 
constructed  of  soft  and  friable  stone  may  be  preserved  in  a  great  measure  from 
decay  and  the  action  of  the  weather  by  a  coating  of  soluble  glass/  For  prac- 
tical purposes,  soluble  glass  is  formed  by  fusing  together  8  parts  of  carbonato 
of  soda  (or  10  of  carbonate  of  potash)  with  15  parts  of  pure  sand,  and  1  of 
charcoal.  The  product,  when  pure,  resembles  ordinary  glass,  but  dissolves 
in  boiling  water  without  residue. 

"When  a  solution  of  soluble  glass  is  rendered  acid  by  the  addition  of  hydro- 
chloric acid,  the  silica  after  a  little  time  separates  as  a  transparent,  tremu- 
lous jelly.  This  is  a  hydrate  of  silica,  which  once  precipitated  in  this  manner, 
is  no  longer  soluble  in  either  water  or"  acids.  By  preventing  the  escape  of 
moisture,  it  may  be  preserved  in  a  gelatinous  condition  ;  but  if  once  allowed 
to  dry,  it  forms  a  white,  gritty  powder — white  siliciotts  sand. 

Most  natural  waters  contain  a  little  soluble  silica,  which  can  be  only  separ- 
ated by  evaporating  the  water  to  dryness.  Waters  which  contain  alkaline 

QtTE6TioX8.— What  are  illustrations?  What  is  Saul  of  sUkri  in  the  animal  kingdom? 
What  are  the  properties  of  silica  ?  Is  silica  an  acid  ?  Under  what  circumstances  does  it 
pass  into  solution  ?  What  is  soluble  glass?  What  are  its  properties  and  uses?  How 
may  silica  be  separated  from  its  solution  in  alkalies?  Does  silica  exist  in  natural  waters  ? 


SILICON. 


281 


FIG.  is  T. 


carbonates  dissolve  it  more  freely,  and  when  the  action  of  the  alkaline  liquid 
is  aided  by  that  of  a  high  temperature,  as  is  the  case  with  the  Geysers,  or  hot 
springs  of  Iceland,  very  large  quantities  of  silica  are  dissolved.  As  the  liquid 
cools,  the  silica  is  deposited,  in  an  insoluble  form,  on  the  surrounding  objects 
in  contact  with  the  waters,  forming  "petrifactions."  Agates,  chalcedony, 
carnelian,  and  onyx,  have  undoubtedly  been  thus  formed  by  the  slow  deposi- 
tion of  silica  from  its  solution  in  water. 

The  acid  character  of  silica  is  especially  exhibited  when  it  is  exposed,  in 
contact  with  other  salts,  to  a  high  temperature.  It  then  displaces  the  most 
powerful  acids  from  their  combinations,  and  uniting  with  then*  bases,  forms 
silicates.  Thus  when  carbonate  or  sulphate  of  potash,  soda,  or  lime,  are  mixed 
with  silica  and  fused,  the  silicic  acid  displaces  the  carbonic  and  sulphuric 
acids  from  their  combinations,  and  forms  silicates  of  potash,  soda,  or  lime.  All 
the  forms  of  clay,  feldspar,  mica,  hornblende,  and  a  great  number  of  our  most 
common  minerals,  are  the  salts  of  silicic  acid.* 

415.  Fluoride  of  S  i  1  i  c  o  n,  Si  Fe ,  —  Fluosilicic  Acid. —In  order 
to  prepare  this  gas,  equal  parts  of  finely-powdered  fluor-spar  and  silicioua 
sand,  or  powdered  glass,  are  mixed  in  a 
capacious  flask,  with  six  parts  of  concen- 
trated sulphuric  acid.  On  the  application  of 
heat,  hydrofluoric  acid  is  liberated,  and  this 
immediately  attacking  the  silica,  produces  a 
colorless  gas,  of  which  silicon  is  a  constitu- 
ent. When  passed  into  water,  the  gas 
is  decomposed,  silicon  is  precipitated  in  the 
form  of  gelatinous  silica,  and  the  water 
becomes  a  solution  of  hydrofluosilicic  acid. 
This  reaction,  which  constitutes  a  very  inter- 
esting experiment,  may  be  easily  exhibited 
by  an  arrangement  of  apparatus  as  repre- 
sented in  Fig.  137. 

In  transmitting  the  gas  into  water,  the  ex- 
tremity of  the  evolution  tube  should  not  be 
brought  into  direct  contact  with  the  water,  \ 
lest  it  become  at  once  obstructed  by  the  de-  ] 
posited  silica ;  but  it  should  be  plunged  j 
beneath  the  surface  of  a  little  mercury  contained  hi  the  bottom  of  the  receiv- 

*  The  composition  of  many  of  the  silicious  minerals  is  extremely  complex,  and  in  a 
scientific  point  of  view,  extremely  interesting.  Upon  one  group  alone,  the  zeolites — hy- 
drated  silicates  of  alumina,  with  lime,  potash  and  soda — an  immense  amount  of  labor  has 
been  expended  by  many  of  the  most  eminent  chemists  of  the  present  century,  and  yet  their 
chemical  formula  and  most  natural  relations  are  still  open  to  question. 

QUESTIONS. — Explain  the  circumstances.  What  is  the  supposed  origin  of  agates,  car- 
nelians,  etc.  ?  When  is  the  acid  character  of  silica  especially  manifested  ?  Illustrate. 
What  are  examples  of  natural  silicates?  What  is  said  of  fluosilicic  acid?  What  occurs 
•when  this  gas  is  passed  into  water  ? 

23* 


282  INORGANIC    CHEMISTRY. 

ing  vessel,  as  is  represented  in  Fig.  137.  As  the  gas  ascends  through  the  mer- 
cury, and  enters  the  water,  it  exhibits  a  most  curious  phenomenon ;  each  bub- 
ble becoming  invested  with  a  white  bag  of  silica,  and  rising,  like  a  miniature 
balloon,  to  the  surface ;  it  often  happens,  also,  in  the  course  of  the  experiment, 
that  the  gas  forms  tubes,  or  conduit  pipes  of  silica  in  the  water,  through 
which  it  gains  the  surface  without  decomposition. 


SECTION    XIV. 

CARBON. 

Equivalent,  6.     Symbol,  C.     Specific  gravity  as  diamond,  3-3  to  3 -5. 

416.  History, — Carbon  is  one  of  the  most  abundant  and 
important  of  the  elementary  bodies.      In  the  inorganic 
kingdom  of  nature  it  exists  chiefly  as  mineral  coal ;  in  the 
state  of  carbonic  acid  diffused  throughout  the  atmosphere  ; 
and  as  a  constituent  of  the  great  rock  masses — carbonates 
of  lime  and  magnesia.     In  the  organic  kingdom,  it  is  the 
characteristic  ingredient  of  all  substances  which  are  pro- 
duced directly  or  indirectly  from  animal  or  vegetable  or- 
ganisms. 

Carbon  is  found  pure  in  nature  in  three  allot ropic  forms 
or  conditions,  each  of  which,  although  possessed  of  identi- 
cally the  same  chemical  composition,  exhibits  properties, 
singularly  different  from  the  others,  and  peculiar  to  itself. 
These  are,  1.  The  Diamond  ;  2.  Graphite,  or  Plumbago  ; 
3.  Mineral  Coal  and  Charcoal. 

417.  The  Diamond  is  pure  carbon,  crystallized. 

It  is  found  throughout  a  wide  extent  of  country  in  India,  but  chiefly  at 
Golconda,  and  in  certain  districts  of  Borneo  and  Brazil.  It  has  also  been 
found  associated  with  gold  and  platinum  in  the  Ural  mountains,  and  in  a  few 
instances  in  the  United  States,  principally  in  the  gold  districts  of  North  Car- 
olina.* In  only  a  few  instances  has  the  diamond  ever  been  found  imbedded 
in  rock  masses,  but  it  is  usually  associated  with  materials  transported  by 
water  from  a  distance,  such  as  loose  sand  and  rolled  gravel  In  their  natural 


*  The  largest  diamonds  come  from  Golconda,  but  Brazil  furnishes  the  greatest  quan- 
tity. The  yearly  produce  of  the  Brazilian  mines  at  the  present  time  is  estimated  at  from 
10  to  13  IDS.,  a  large  proportion  of  which,  however,  are  unfit  tor  jewelry. 

QUESTIONS. — "What  is  said  of  the  distribution  of  carbon  in  the  two  great  kingdoms  of 
nature  ?  In  what  conditions  is  carbon  found  pure  naturally  ?  What  is  the  diamond  ? 
Under  what  circumstances  is  it  found  in  nature  ? 


CARBON.  283 

condition,  diamonds  have  usually  the  appearance  of  semi-transparent,  rounded 
pebbles,  and  are  covered  by  a  thin,  opaque  crust ;  on  removing  this  crust, 
their  exceeding  brilliancy  becomes  apparent. 

The  diamond  is  generally  colorless,  and  such  specimens  possess  the  great- 
est value ;  but  it  is  not  unfrequently  found  of  a  blue,  yellow,    -pIG 
or  rose  color,  and  sometimes  green  or  black. 

The  primitive  form  of  the  diamond  is  that  of  an  octohedron 
(see  Fig.  138),  but  its  faces  are  often  convex,  and  its  edges 
rounded.  It  is  cut  for  jewelry  in  three  forms,  known  as  bril- 
liants, Fig.  139,  roses,  Figs.  140,  141,  and  tables,  Figs.  142,  143.* 

Fig.  139.  Fig.  140.  Fig.  141.  Fig.  142.  Fi«r.  14? 


The  diamond  is  the  hardest  of  all  known  substances,  and  can  be  only  cut 
or  abraded  by  means  of  its  own  powder — inferior  and  imperfect  stones  being 
broken  down  for  this  purpose.  The  process  of  cutting  is  effected  by  a  hori- 
zontal disc  of  steel,  covered  with  diamond  dust  and  oil,  and  revolving  with  a 
velocity  of  two  or  three  thousand  times  per  minute.  The  gem  is  fixed  in  a 
mass  of  lead,  which  is  fitted  to  an  arm,  one  end  of  which  rests  upon  a 
table  over  which  the  plate  revolves,  while  the  other,  sustaining  the  diamond, 
is  pressed  upon  the  plate  by  movable  weights,  at  the  discretion  of  the  ope- 
rator. The  gem,  however,  cannot  be  ground  into  any  form  at  pleasure,  but 
only  in  directions  parallel  to  its  lines  of  cleavage.  (§  73.)f 


*  The  form  of  the  brilliant  shows  the  gem  to  the  best  advantage,  and  maybe  recognized 
by  its  flat  summit ;  the  surface  of  a  rose  diamond  is  covered  with  equilateral  triangles, 
terminating  in  a  sharp  point.  The  table  form  is  only  given  to  plates,  laminae,  or  slabs  of 
diamonds,  which  have  a  small  depth  compared  to  their  superficial  extent.  The  brilliant 
and  the  rose  lose  in  cutting  and  polishing  somewhat  less  than  half  their  weight,  so  that 
the  value  of  a  cut  stone  is  double  that  of  an  uncut  one,  without  reckoning  the  expense  of 
the  process. 

t  The  method  of  cutting  diamonds  was  discovered  in  1456,  and  is  still  unknown  in  its 
perfection  among  Eastern  nations.  The  business  in  Europe  is  carried  on  almost  exclu- 
sively in  Amsterdam,  Holland.  The  heat  developed  in  the  cutting  is  frequently  so  great 
as  to  melt  the  lead  in  which  the  diamond  is  imbedded,  and  the  time  occupied  in  cutting  a 
single  face  varies  from  3  to  30  hours. 

The  weight  of  diamonds  is  estimated  in  carats — 150  of  which  are  equal  to  1  ounce  Troy, 
or  430  grains.  "  The  rule  for  estimating  the  value  of  diamonds  is  peculiar,  and  supposing 
the  gems  under  comparison  to  be  equal  in  quality,  may  be  expressed  as  being  in  the  ratio 
of  the  squares  of  their  respective  weights.  Thus,  supposing  three  diamonds  to  exist, 
weighing  respectively  1,  2,  and  3  carats ;  their  respective  values  would  be  as  one,  four, 
and  nine.  This  rule,  however,  can  only  be  considered  as  applying  to  gems  of  a  moder- 
ate size ;  as  very  large  diamonds,  if  estimated  according  to  this  mode  of  calculation, 
would  become  expensive  beyond  the  means  of  the  richest  to  command." 

QUESTIONS.— What  is  its  primitive  form?  In  what  three  forms  is  it  cut  for  jewelry? 
What  is  said  of  its  hardness  ?  How  is  it  cut  ? 


284  INORGANIC     CHEMISTRY. 

The  diamond  is  remarkably  indestructible,  and  is  not  acted  upon  by  any 
solvent,  neither  is  it  affected  by  heat  alone — since  it  may  be  heated,  when 
removed  from  the  access  of  air,  to  a  white  heat  without  injury.  In  the  open 
air  it  burns  at  about  the  melting  point  of  silver,  and  is  converted  into  coal, 
or  carbonic  acid  gas. 

Many  attempts  have  been  made  to  fuse  or  crystallize  some  pure  form  of 
carbon,  or,  in  other  words,  to  manufacture  diamonds,  but  they  have  all  failed. 
In  1853,  M.  Despretz  of  Paris  succeeded,  after  long-continued  voltaic  action, 
in  depositing  at  one  of  the  terminal  poles  of  a  galvanic  battery  a  quantity  of 
carbon  in  the  form  of  minute  microscropic  grains ;  these  grains  appeared  to  be 
octohedral  crystals,  and  were  capable  of  cutting  and  polishing  diamonds  and 
rubies ;  hence  it  has  been  inferred  that  they  were  actually  themselves  dia- 
monds. 

The  origin  of  the  diamond  has  been  a  subject  of  much  curious  speculation, 
inasmuch  as  the  circumstances  under  which  it  is  found  in  nature  afford  us 
no  clue  to  the  process  of  its  formation.  The  structure  of  the  diamond  itself, 
however,  furnishes  us  with  some  positive  information  on  the  subject,  and  in- 
dicates that  it  is  a  product,  either  directly  or  indirectly,  of  the  vegetable  king- 
dom.* Sir  David  Brewster,  who  has  given  much  attention  to  the  subject, 
is  inclined  to  the  opinion,  that  the  diamond  is  a  drop  of  fossilized  gum,  anal- 
ogous in  some  respects  to  amber. 

418.  The  largest  known  diamond  is  an  uncut  gem  belonging  to  the 
crown  jewels  of  Portugal.  It  was  found  in  Brazil  about  the  year  1808,  and 
weighs  1,680  carats,  or  about  11  ounces.  About  the  middle  of  the  16th 
century  a  diamond  was  found  at  Grolconda  in  India,  which  had  the  form  of 
half  a  hen's  egg,  and  weighed  nearly  6  ounces.  This  diamond,  wliich  was 
long  known  as  the  Great  Mogul  from  its  possessor,  has  disappeared,  and  is 
supposed  to  have  been  broken  up ; — the  separate  pieces,  according  to  this 
theory,  now  constituting  three  of  the  largest  existing  diamonds,  viz.,  1,  the 
great  diamond  in  the  possession  of  Russia,  weighing  196  carats :  2d,  the 
Koh  i-noor,  in  the  possession  of  the  Queen  of  England,  which  weighed  before 
cutting  186  carats,  and  after  cutting  103  carats;  and  3d,  a  diamond  belonging 
to  the  Shah  of  Persia,  of  the  weight  of  130  carats.  The  value  of  the  Eussian 
diamond  has  been  estimated  at  20  millions  of  dollars,  and  that  of  the  Koh- 
i-noor  at  from  3  to  10  millions. 

The  other  large  diamonds  most  worthy  of  notice  are  the  following : — A 
yellow  diamond  belonging  to  the  crown  of  Austria,  which  weighs  139  carats. 
The  size  and  form  of  this  diamond,  which  was  once  sold  as  a  bit  of  colored 


*  The  evidence  on  this  point  is  principally  as  follows  ;  diamonds  have  been  found  in- 
closing vegetable  matter,  and  when  the  diamond  is  burned  a  minute  yellowish  ash  is  left, 
which  generally  possesses  a  cellular  structure.  Some  other  proof  is  also  afforded  by  the 
action  of  refracted  and  polarized  light. 

QUESTIONS.—  What  is  said  of  its  indestructibility?  Have  any  attempts  been  made  to 
manufacture  diamonds  ?  "What  is  said  of  the  origin  of  the  diamond  ?  What  evidence 
have  we  on  the  subject  ?  How  large  a  diamond  has  ever  been  found  ?  What  are  some 
of  the  most  valuable  diamonds  ? 


CARBON.  285 

Fro.  144  glass,  are  represent-  FIG   145 

ed  in  Fig.  144.  The 
Pitt  or  Regent  dia- 
mond belonging  to 
France,  is  repre- 
sented in  Fig.  145. 
the  dotted  line  be- 
ing the  outline  of 
the  stone  before  cut- 
ting. This  diamond, 

Which  is  a  light  blue  color,  is  allowed  to  be  the 
finest  in  existence,  and  weighs  131  carats.  It  was  brought  from  India  by  a 
Mr.  Pitt,  and  sold  to  the  Regent  of  France  in  1*717  for  about  $700,000.  Its 
value,  as  estimated  by  a  commission  of  Parisian  jewelers,  is  about  $3,000,000. 
~  Fig.  146  represents  a  very  beautiful  diamond  known 

as  the  Pigott  diamond,  which  weighed  47  carats, 
and  was  sold  for  about  $120,000.* 

419.  Graphite,  or  Plumbago,  is  the 
^^L^^r  second  allotropic  form  in  which  car- 
bon occurs  uncombined  in  nature.  It 
has  a  metallic,  leaden-gray  luster,  feels  unctuous  to  the 
touch,  and  is  generally  known  as  "  black-lead/'  although 
it  has  no  trace  of  lead  in  its  composition. 

It  is  found  chiefly  in  the  older  rocks  (in  many  localities  in  the  United 
States),  chiefly  in  beds  or  rounded  masses,  but  sometimes  crystallized  in  flat 
six-sided  prisms.  It  is  never  found  perfectly  pure,  but  usually  contains  a 
little  iron  and  some  other  accidental  impurities.  Like  the  diamond,  it  can  not 
be  fused  or  volatilized  by  the  action  of  the  most  intense  heat ;  it  burns,  how- 
ever, in  oxygen  gas,  forming  carbonic  acid. 

The  principal  use  to  which  plumbago  is  practically  applied  is  for  the  manu- 
facture of  "  lead  pencils."  Most  of  the  ordinary  pencils  now  used  are  manu- 
factured from  a  factitious  paste,  made  of  powdered  plumbago,  antimony,  and 
sulphur  fused  together,  and  cast  into  blocks.  These  blocks  are  then  sawed 
into  small  rectangular  prisms,  which  are  subsequently  inclosed  in  cylinders  of 
cedar  wood.  The  best  drawing-pencils  are,  however,  made,  by  reducing  the 
plumbago  to  a  fine  powder,  freeing  it  from  impurities,  and  then  subjecting  it 
to  enormous  hydrostatic  pressure,  simultaneously  with  the  abstraction  of  all 
remaining  traces  of  air  by  means  of  an  air-pump.  A  coherent  block  is  thus  ^ 

*  This  diamond  is  not  in  existence,  but  was  destroyed  by  a  Turkish  pasha  in  order  to 
prevent  it  from  falling  into  the  hands  of  his  enemies. 

So  rare  are  diamonds  of  large  size,  that  it  is  stated  that  the  whole  number  known  to 
exceed  33  carats  in  weight  does  not  exceed  nineteen. 

QUESTIONS.— What  is  graphite?  In  what  conditions  does  it  occur  in  nature?  What 
is  said  of  its  infusibility  ?  What  of  its  practical  applications  ? 


286  INORGANIC     CHEMISTRY. 

obtained,  which  is  subsequently  sawed  into  bars.  The  particles  of  plumbago, 
although  apparently  very  soft,  are  in  reality  extremely  hard,  and  the  steel 
saws  employed  to  cut  it  rapidly  wear  out.  Plumbago  is  also  used  for  the 
manufacture  of  melting  pots  or  crucibles,  for  the  lubrication  of  the  bearing  sur- 
faces of  machinery,  and  for  imparting  a  luster  to  iron. 

Several  modifications  of  graphite  may  be  procured  artificially.  "When  cast 
iron  is  melted  with  an  excess  of  charcoal,  it  dissolves  a  portion  of  the  carbon. 
This  carbon,  when  the  iron  is  allowed  to  cool  slowly,  crystallizes  out  in  the 
form  of  large  and  beautiful  leaflets  of  graphite. 

420.  Gas  Carbon  , — Another  exceedingly  interesting  variety  of  graphite 
is  formed  in  the  interior  of  the  retorts  used  for  the  production  of  coal-gas. 
This  substance  (which  may  be  procured  in  abundance  at  all  gas-works)  is 
known  as  "  gas  carbon."  It  possesses  a  luster  resembling  that  of  a  metal,  a 
hardness  sufficient  to  enable  it  to  scratch  glass,  and  is  one  of  the  purest  forms 
of  carbon. 

'  421.  Coal. — The  third  allo tropic  modification  of  carbon 
includes  all  the  varieties  of  mineral  coal,  wood,  charcoal, 
lamp-black,  soot,  animal  charcoal,  etc.,  etc. 

422.  Mineral  Coal  is  the  product  of  an  accumulated 
vegetation,  which  flourished   mainly  during  a  particular 
period  of  the   earth's  history,  known  in  geology  as  the 
"carboniferous  epoch.'' 

It  occurs  on  the  earth  in  veins,  or  strata,  enclosed  between  other  strata  of 
limestone,  clay-slate,  or  iron  ore. 

"We  know  that  coal  is  of  vegetable  origin,  because  in  every  coal-mine  we 
find  leaves,  trunks,  and  fruits  of  trees  in  immense  numbers,  many  of  them  in 
the  most  perfect  state  of  preservation ;  so  much  so,  that  the  botany  of  tho 
coal  period  can  be  studied  with  nearly  as  much  certainty  as  the  botany  of  any 
given  section  of  the  present  surface  of  the  earth ;  and,  furthermore,  whenever 
coal  has  not  been  too  much  changed  by  heat  and  pressure,  a  thin  layer  of  it 
exhibits,  under  the  microscope,  all  the  ducts  and  vessels  of  the  plant  to  which 
it  originally  belonged. 

Coal  consists,  like  vegetable  matter  in  general,  of  carbon,  hydrogen,  and 
oxygen,  with  a  small  proportion  of  nitrogen.  It  contains,  in  addition,  variable 
quantities  of  saline  and  earthy  substances,  which  alwaj^s  enter  into  the  com- 
position of  plants.  These  matters,  when  coal  is  burnt,  are  left  unconsumed, 
and,  together  with  some  impurities,  constitute  its  ashes. 

423.  Anthracite   Coal   differs  from  bituminous  in  this  respect — that 
its  original  volatile  constituents,  oxygen,  hydrogen,  etc.,  have  been  mainly 
driven  off  by  the  agency  of  heat,  leaving  carbon  in  a  dense  and  nearly  pure 

QUESTIONS.— How  may  graphite  be  formed  artificially?  What  is  gas  carbon?  What 
are  its  properties  ?  What  is  the  third  allotropic  form  of  carbon  ?  What  is  mineral  coal  ? 
What  proof  have  -we  of  its  vegetable  origin  ?  What  is  the  constitution  of  coal  ?  What 
occasions  the  difference  between  anthracite  and  bituminous  coal  ? 


CAB  BON.  287 

condition  behind  ;  bituminous  coal,  on  the  contrary,  not  having  been  exposed 
to  the  same  degree  of  heat,  retains  its  original  vegetable  constitution  in  a 
great  degree  unaltered.*  When  bituminous  coal  is  ignited,  its  volatile  con- 
stituents are  expelled  by  heat,  and  burn  with  flame  and  smoke;  while  an- 
thracite, from  its  previous  deprivation  of  these  substances,  burns  without  flame 
or  smoke. 

424.  Coke  is  bituminous  coal  heated  apart  from  air,  until  its  volatile  con- 
stituents are  in  a  great  measure  expelled.  It  produces  a  more  steady  and 
intense  heat  than  the  coal  from  which  it  is  derived,  and  evolves  no  smoke. 

425.  Charcoal  is  that  form  of  carbon  which  results  from 
depriving  animal  and  vegetable  substances  of  their  vol- 
atile constituents. 

This  is  usually  effected  by  the  agency  of  heat ;  but  the  application  of  heat 
is  not  essential,  since  wood  immersed  in  sulphuric  acid,  or  buried  for  a  long 
period  in  the  earth,  becomes  converted  into  charcoal. 

Charcoal  is  usually 
prepared  by  firing  wood 
in  mounds  or  pits,  cov- 
ered with  turf  or  soil  in 
such  a  way  as  to  ex- 
clude in  a  great  degree 
the  admission  of  air, 
and  thus  prevent  com- 
plete combustion.  Fig. 
147  represents  the  ar- 
rangement and  con- 
struction of  a  "  charcoal 
mound  or  heap. "  If  the 
diameter  of  the  heap  be  30  feet  or  more,  the  operation  is  not  complete  in  less 
than  a  month,  and  the  slower  the  combustion  the  greater  the  product  of 
charcoal.  When  the  wood  is  thoroughly  charred,  the  admission  of  air  is  en- 
tirely cut  off,  and  the  combustion  ceases.  The  charcoal  produced  retains  the 
form  of  the  wood,  but  is  much  reduced  in  size ;  generally  not  amounting  to 
more  than  three  fourths  of  the  bulk  of  the  wood,  and  never  exceeding  one  fourth 
of  its  weight.  The  nicest  kinds  of  charcoal,  such  as  are  used  in  the  manufac- 
ture of  gunpowder,  are  prepared  by  heating  wood  in  close  iron  cylinders. 

426.  Soot  is  coal  in  a  state  of  minute  division  resulting  from  the  imper- 

*  Wherever  the  strata  inclosing  coal  have  been  disturbed  and  altered  through  the 
agency  of  subterranean  heat,  the  coal  is  generally  anthracite  ;  but  where  the  strata  remain 
undisturbed,  the  coal  is  generally  bituminous.  Thus  in  Pennsylvania,  the  great  coal-fields 
which  are  adjacent  to  the  line  along  which  the  Appalachian  chain  of  mountains  have  been 
elevated,  furnish  only  anthracite  ;  but  as  we  recede  from  the  mountains  and  go  west,  the 
coal  becomes  bituminous. 

QUESTIONS. — What  is  coke?  What  is  charcoal ?  How  may  it  be  prepared ?  What  is 
the  ordinary  process  of  preparing  charcoal  ?  What  is  soot  ? 


INORGANIC     CHEMISTRY. 

feet  combustion  of  carbonaceous  gases.  Lamp-black  is  generally  applied  to 
designate  the  soot  produced  by  the  imperfect  combustion  of  tar  and  resinous 
matters ;  it  is  much  used  in  the  manufacture  of  printers'  ink  and  of  paint. 

Animal  charcoal,  bone-black,  and  ivory-black,  are  names  given  to  the  pro- 
ducts produced  by  heating  bones,  ivory  shavings,  and  like  animal  substances, 
in  close  vessels.  The  charcoal  thus  obtained  is  mixed  with  ten  times  its 
weight  of  phosphate  of  lime. 

427.  Properties  , — Carbon  in  the  form  of  charcoal  is  a  black,  brittle, 
insoluble,  inodorous,  tasteless  substance.  At  ordinary  temperatures  it  has 
little  or  no  affinity  for  the  other  elements,  and  is,  consequently,  one  of  the 
most  unchangeable  of  all  substances.  Grains  of  wheat  charred  at  Hercu- 
laneum  nearly  2,000  years  ago,  still  retain  their  form,  Wooden  posts,  if 
charred  at  the  end  before  being  set  in  the  ground,  are  rendered  far  more  dur- 
able. For  the  same  reason,  it  is  a  common  practice  to  char  the  ulterior  of 
tubs  and  casks  intended  to  hold  liquids. 

Charcoal,  when  subjected  to  the  action  of  the  most  intense  heat,  is  infus- 
ible, and  if  air  be  excluded,  it  remains  unchangeable.* 

At  high  temperatures,  however,  carbon  surpasses  all  other  bodies  in  its 
affinity  for  oxygen,  and  is,  consequently,  more  suitable  than  any  other  sub- 
stance for  depriving  the  metallic  ores  or  oxyds  of  their  oxygen,  and  reducing 
them  to  a  metallic  state — an  operation  termed  smelting. 

The  compounds  of  carbon  with  the  other  elements  are  termed  carburets,  or 
carbides. 

Newly  prepared  charcoal  possesses  the  remarkable  power  of  absorbing  and 
condensing  within  its  pores,  large  quantities  of  certain  gases  and  aqueous  va- 
por. (The  explanation  of  this  phenomenon  has  been  already  given,  §  48.) 
Charcoal  from  hard  wood,  or  that  which  possesses  fine  pores,  exhibits  this 
property  in  the  highest  degree,  and  the  gases  which  are  absorbed  most  abun- 
dantly are  those  which  are  most  readily  liquefied  by  cold  and  pressure ; 
thus  of  ammoniacal  gas  it  absorbs  90  times  its  volume,  of  carbonic  acid,  35 
times;  of  oxygen,  9  times;  of  hydrogen,  1-75  volumes. 

Charcoal  in  a  finely-divided  state  has  also  the  power  of  absorbing  odorifer- 
ous effluvia,  and  the  coloring  principles  of  most  animal  and  vegetable  sub- 
stances. Animal  matter,  in  an  advanced  state  of  putrefaction,  loses  all  offen- 
sive odor  when  covered  with  a  layer  of  charcoal ;  it  continues  to  decay,  but 
without  emitting  any  ill  odor. 


*  An  illustration  of  this  is  found  in  the  fact,  that  charcoal  thrown  into  a  blast-furnace, 
and  its  access  to  air  being  cut  off  by  an  envelope  of  molten  metal,  will  not  unfrequently 
pass  through  the  furnace  unconsumed  and  unaltered. 

QUESTIONS. — What  is  lamp-black  ?  What  is  animal  charcoal  ?  What  are  the  proper- 
ties of  charcoal  ?  What  is  said  of  its  indestructibility  ?  What  of  its  affinities  ?  Why  is 
carbon  uniformly  used  in  the  reduction  of  metallic  ores  ?  What  are  the  compounds  of 
carbon  with  the  metals  called  ?  What  is  said  of  the  absorbing  power  of  charcoal  ?  What 
gases  are  absorbed  most  abundantly  ?  What  is  said  of  its  deodorizing  and  decolorizing 
agency  ?  What  are  illustrations  of  its  deodorizing  action  ? 


CARBON. 


289 


Advantage  has  been  taken  of  this  property  of  charcoal  to  construct  a  res- 
pirator for  protection  against  the  inhalation  of  malarious  and  infected  air.  It 
consists  of  a  hollow  case  of  wire-gauze  filled  with  coarsely -powdered  charcoal, 
and  fitted  over  the  mouth  and  nostrils  by  FIG.  148, 

straps,  as  is  represented  in  Fig.  148.  All 
the  air  that  enters  the  lungs  must  pass 
through  this  charcoal  seive,  and  in  so  passing, 
is  deprived  of  the  noxious  vapors  or  gases  it 
may  contain.  For  persons  engaged  in  hos- 
pitals, dissecting-rooms,  the  holds  of  ships,  or 
in  the  vicinity  of  sewers,  this  device  is  most 
valuable.  Foul  water  filtered  through  a 
layer  of  powdered  charcoal,  is  decolorized  and 
purified.  This  action  of  charcoal  may  be  il- 
lustrated by  agitating  water  containing  sul- 
phuretted hydrogen  in  solution,  with  a  small 
quantity  of  freshly-burned  powdered  charcoal ;  the  offensive  odor  will  com- 
pletely disappear.  Sugar-refiners  render  brown  sugar  white  by  passing  it  in 
solution  through  animal  charcoal.  Ale  and  porter,  subjected  to  the  same 
FiG.  149.  treatment,  are  not  only  decolorized,  but  deprived  of 

their  bitter  principles.  In  case  of  poisoning  with 
vegetable  poisons,  such  as  opium,  morphia,  strych- 
nia, etc.,  one  of  the  best  immediate  antidotes  which 
can  be  given  is  powdered  charcoal  in  water:  this 
absorbs  the  poisonous  principle,  and  renders  it  inac- 
tive. The  decolorizing  action  of  charcoal  may  be 
illustrated  by  filtering  porter,  port-wine,  or  water 
colored  with  ink,  through  a  small  quantity  of  animal 
charcoal  (See  Fig.  149.)  The  filtered  liquor  will 
be  deprived  of  smell,  taste,  and  color. 

Charcoal  loses  its  absorptive  and  decolorizing 
properties  by  use ;  but  on  heating  it  afresh,  it  re- 
gains them. 

Carbon  in  the  form  of  the  diamond  ig  a  non-conductor  of  electricity;  but  in 
all  its  other  forms  it  is  an  excellent  conductor,  ranking  next  to  the  metals  in 
this  respect.  In  a  state  of  fine  subdivision,  carbon  is  a  bad  conductor  of  heat, 
but  its  conducting  power  increases  with  its  density. 

428.  Compounds  of  Carbon  and  Oxygen . — The  compounds 
of  carbon  with  oxygen  and  hydrogen,  and  with  oxygen,  hydrogen,  and  nitro- 
gen, are  innumerable,  and  constitute  the  great  bulk  of  the  substance  of  all 
vegetable  and  animal  products.  The  consideration  of  these  compounds  be- 


QUESTIONS.— What  advantage  has  been  taken  of  this  property  ?  What  are  illustrations 
of  the  decolorizing  action  of  charcoal?  Under  what  circumstances  may  charcoal  act  as  an 
antidote  for  poisons  ?  What  is  said  of  the  conducting  powers  of  carbon  for  heat  and  elec- 
tricity ?  What  is  said  of  the  compounds  of  carbon  with  oxygen  ? 


290 


INORGANIC    CHEMISTRY. 


longs  mainly  to  organic  chemistry.  "With  ox ygon  alone  carbon  unites  directly 
to  form  on]y  two  compounds — carbonic  oxycl  and  carbonic  acid.  Their  com- 
position may  bo  represented  as  follows : — 

Composirion  by  weight. 


Symbol. 

Carbonic  oxyd CO 

Carbonic  acid , CO-2 


C  carbon,    -j-    8  oxygen. 
6        "         4-16       " 


429.  Carbonic  Acid,  C  Oa.  is  the  sole  product  of  the  com- 
bustion of  pure  carbon  in  oxygen  gas  or  atmospheric  air. 
It  is  also  produced  abundantly  by  all  the  ordinary  pro- 
cesses of  combustion,  by  respiration,  fermentation,  and  by 
the  decay  of  animal  and  vegetable  products.  It  exists  in 
a  free  state  in  the  atmosphere,. and  in  the  earth  in  im- 
mense quantities,  chiefly  in  combination  with  lime,  form- 
ing carbonate  of  lime  (marble,  chalk,  etc.,  etc.). 

For  an  account  of  its  discovery  see  §  329. 

430.-  Preparation . — Carbonic  acid  may  be  prepared  by  burning  char- 
coal in.  oxygen  gas  (p.  190) ;  or  by  allowing  a  candle  to  burn  as  long  as  it 
•will  in  a  closed  bottle  or  jar  filled  with  air.  Practically,  however,  it  is  ob- 
tained in  a  pure  state,  much  more  conveniently.  It  being  a  feeble  acid, 
almost  every  other  acid,  which  dissolves  freely  in  water,  is  able  to  expel  it 
from  its  compounds;  it  is,  therefore,  easily  separated  from  its  compounds  by 
the  addition  of  any  of  the  common  acids.  Thus,  fragments  of  chalk  or  mar- 
ble, with  a  little  water,  are  placed  in  an  open-mouth  bottle,  or 
in  an  evolution  flask  (see  Fig.  150,  also  Fig.  95),  and  dilute 
sulphuric  or  hydrochloric  acid  added.  The  acid  seizes  upon 
the  lime,  and  displaces  the  carbonic  acid,  which  escapes  with 
an  effervescence.  It  may  be  collected 
in  the  usual  way  over  water,  or  in 
dry  bottles,  by  the  displacement  of 


PIG.  150. 


FIG.  151. 


air. 


431.  Properties,  —  At  ordin- 
ary temperatures  and  pressures,  car- 
bonic acid  is  a  colorless,  transparent  gas,  of  a 
pungent  odor,  and  acidulous  taste.     It  is  more  than  hnlf  as 
heavy  again  as   atmospheric  air,   its   specific  gravity  being 
1-529  (air  =  1*000);  by  reason  of  its  great  density,  it  may  be 
poured  from  one  vessel  into  another  like  water.     (See  Fig. 
151.) 

Carbonic  acid  is  not  inflammable,  and  extinguishes  the  flame  of  burning 
bodies,  even  when  largely  diluted  with  air,  for  a  candle  will  not  burn  in  a 

QUESTIONS. — What  is  the  composition  of  carbonic  acid  ?  What  is  said  of  its  formation 
and  distribution  ?  How  may  it  be  prepared  ?  How  is  it  obtained  practically  ?  What  are 
its  properties  ?  What  is  said  of  its  density  ?  What  of  its  relation  to  combustion  ? 


CARBON.  291 

mixture  of  4  volumes  atmospheric  air,  and  1  volume  of  carbonic  acid.*  This 
property  may  be  strikingly  illustrated  by  placing  a  lighted  candle  at  the  bot- 
tom of  a  deep  jar,  and  then  pouring  carbonic  acid  from  another  vessel  upon 
it,  as  is  represented  in  Fig.  151.  The  light  will  be  extinguished  as  soon  as 
the  gas  reaches  the  flame. 

Carbonic  acid  in  its  pure  state  is  irrespirable,  producing,  the  moment  it  is 
inhaled,  a  spasm  of  the  glottis,  which  closes  at  once  the  air  passages  of  the 
lungs :  an  animal  immersed  in  it,  therefore,  dies  of  suffocation.  "When  di- 
luted with  air,  it  may  be  breathed  without  difficulty,  but  if  the  proportion  in 
which  it  exists  in  the  air  exceeds  4  per  cent.,  it  acts  as  a  narcotic  poison.f  A 
proportion  of  10  to  12  per  cent,  is  speedily  destructive  to  animal  life,  and  even 
so  small  a  quantity  as  1  or  2  per  cent,  is  deleterious  and  depressing.  The 
drowsiness  and  headache  experienced  in  crowded  and  ill- ventilated  apart- 
ments are  chiefly  duo  to  the  accumulation  of  carbonic  acid  as  the  resulting 
product  of  respiration. 

Many  persons  have  lost  their  lives,  either  intentionally  or  by  accident,  by 
sleeping  in  a  confined  room  with  a  pan  of  burning  charcoal ;  also  from  de- 
scending into  wells,  mines,  vats,  and  sewers  in  which  carbonic  acid  has  accu- 
mulated. Accidents  of  the  latter  character  may  be  prevented  by  taking  the 
precaution  to  lower  a  lighted  candle  into  the  well  or  vat  suspected  to  contain 
this  gas,  before  descending  into  it;  if  the  light  remains  undiminished,  all  may 
bo  considered  safe ;  but  if  the  flame  be  extinguished,  or  even  sensibly  im- 
paired, there  is  evident  danger.  "Wells,  pits,  etc.,  containing  carbonic  acid 
may  be  freed  from  it  by  lowering  into  them  pans  of  recently-burned  pulver- 


*  This  property  of  carbonic  acid  has  been  practically  applied  for  the  extinguishment 
of  fires  in  coal-mines — a  stream  of  carbonic  acid,  generated  by  passing  air  through  a  fur- 
nace of  coal,  being  blown  into  the  mine  until  all  its  passages  were  filled  with  it,  and  the 
'combustion  arrested.  In  this  way,  a  coal-mine  in  England  that  had  been  on  fire  for  thirty 
years,  and  had  extended  over  twenty-six  acres,  was  extinguished  in  1851.  About  8,000,000 
cubic  feet  of  gas  were  required  to  fill  the  mine,  and  a  continuous  stream  of  impure  car- 
bonic acid  was  forced  in  by  the  agency  of  a  steam-jet,  day  and  night,  for  about  three 
weeks.  The  difficulty  lay  not  so  much  in  putting  out  the  fire,  as  in  cooling  down  the  ignited 
mass,  so  that  it  should  not  again  burst  into  a  flame  on  the  readmission  of  air,  and  in  order 
to  effect  the  necessary  reduction  of  temperature,  water  was  blown  in  along  with  the  carbonic 
acid,  in  the  form  of  a  fine  spray,  or  mist.  Subsequently,  cold  air  mixed  with  the  spray 
was  thrown  in ;  and  in  a  month  from  the  commencement  of  operations,  the  fire  was  found 
to  be  completely  extinguished. 

A  portable  arrangement  for  extinguishing  fires,  termed  the  "Fire  Annihilator,"  em- 
bodies the  same  principles.  It  consists,  essentially,  of  a  tin  or  sheet-iron  case,  containing 
ft  substance  holding  carbonic  acid  in  combination,  together  with  a  bottle  of  sulphuric  acid. 
P.y  means  of  a  simple 'arrangement,  this  bottle  of  acid  may  be  broken,  when  its  contents, 
mixing  with  the  solid,  evolve  carbonic  acid ;  and  this,  flowing  out  from  apertures  in  the 
case,  fills  the  apartment,  and  extinguishes  the  fire. 

t  By  a  narcotic  poison  we  understand  one  which  produces  sleep  and  insensibility,  ter- 
minating, if  taken  in  sufficient  quantity,  in  death.  Opium  and  morphia  are  examples. 

QUESTIONS. — What  of  its  relation  to  respiration  ?  What  are  illustrations  of  the  poison- 
ous influence  of  carbonic  acid  ?  What  precautions  should  be  taken  before  descending  into 
wells,  sewers,  etc.  ? 


292  INORGANIC     CHEMISTRY. 

ized  charcoal,  or  fresh,  slacked  lime,  or  by  showering  down  cold  water— all  of 
which  substances  absorb  the  gas  freely. 

To  resuscitate  those  who  have  been  exposed  to  the  poisonous  action  of 
carbonic  acid,  dash  cold  water  upon  them  freely,  and  assist  the  circulation  by 
friction  of  the  extremities. 

432.  Water  at  ordinary  temperatures  and  pressures  absorbs  about  two 
thirds  of  its  bulk  of  carbonic  acid ;  but  it  will  take  Up  much  more  if  the  pres- 
sure be  increased.  The  quantity  absorbed  is  in  exact  ratio  with  the  compres- 
sing force,  the  water  dissolving  twice  its  volume  when  the  pressure  is  doubled, 
and  three  times  its  volume  when  the  pressure  is  trebled.  On  removing  tho 
pressure  the  greater  part  of  the  gas  escapes,  and  produces  that  effervescence 
which  we  see  when  a  bottle  of  ginger-beer,  soda-water,  cider,  or  champagne 
is  opened. 

Most  of  the  beverage  sold  under  the  name  of  soda-water  does  not  contain 
a  particle  of  soda,  but  is  merely  water  impregnated,  by  mechanical  pressure, 
with  about  eight  times  its  bulk  of  carbonic  acid.  In  fermenting  liquors  in- 
closed in  bottles,  on  the  contrary,  the  carbonic  acid  is  gradually  evolved  by 
the  process  of  fermentation  in  the  interior  of  the  bottle.  As  fast  as  it  is  set 
free,  the  liquor  dissolves  it,  the  pressure  of  the  gas  upon  the  inner  surface  of 
the  bottle  increasing  at  the  same  time.  The  pressure  thus  generated  is  enor- 
mous, and  beyond  a  certain  limit  the  cork  will  either  be  forced  out,  or  the 
bottle  will  burst.  If  the  cork  be  withdrawn,  the  confined  gas  will  drive  out 
the  liquor  in  its  own  eagerness  to  escape.  The  manufacture  of  champagne  is 
always  carried  on  in  vaults  far  below  the  surface  of  the  earth,  in  order  to 
secure  a  low,  and  at  the  same  time  a  uniform  temperature.  The  reason  of  this 
is,  that  the  absorption  of  carbonic  acid  by  the  liquor  is  greatly  assisted  by  a 
reduction  of  temperature,  and  a  rise  of  a  few  degrees  of  the  thermometer  in 
the  vault  is  sometimes  accompanied  by  the  breakage  of  thousands  of  bottles. 

Fermented  liquors,  by  the  escape  of  their  carbonic  acid,  are  rendered  flat 
and  insipid.  A  thick,  viscid,  or  glutinous  liquor,  like  porter  or  ale,  retains 
the  little  bubbles  of  carbonic  acid  as  they  rise  through  it,  and  is  thereby 
caused  to  froth ;  but  a  thin  liquor,  like  champagne  or  cider,  which  allows  tho 
bubbles  to  escape  freely,  only  sparkles. 

A  solution  of  carbonic  acid  in  water  has  a  pleasant,  acid  taste,  and  tem- 
porarily reddens  blue  litmus  paper.  The  solvent  powers  of  such  a  solution 
are  far  more  extensive  than  those  of  pure  water ;  and  the  hardest  rocks  and 
minerals  are  gradually  disintegrated  and  broken  down  by  the  long-continued 
action  of  water  charged  with  a  small  proportion  of  this  gas. 

433.  Solidification  of  Carbonic  Acid,— When  carbonic 
acid  at  32°  F.  is  subjected  to  a  pressure  of  36  to  38  at- 

QUESTKXNS. — What  is  the  antidote  against  poisoning  with  carbonic  acid  ?  What  is  said 
of  the  absorption  of  carbonic  acid  by  water  ?  What  is  ordinary  "  soda-water?"  What  is 
the  source  of  carbonic  acid  in  fermenting  liquors  ?  What  takes  place  when  a  fermenting 
liquor  is  bottled  ?  When  does  a  liquor  froth,  and  when  sparkle?  What  is  said  of  tho 
solvent  power  of  carbonic  acid  in  solution  ?  What  is  said  of  the  solidification  of  carbonic 
acid? 


CARBON. 


293 


mospheres,  it  condenses  into  a  liquid  as  transparent  and 
colorless  as  water.  If  a  stream  of  liquefied  acid  be  allowed 
to  escape  into  the  air,  it  freezes  by  its  own  evaporation 
into  a  white,  snow-like  solid.* 

*  The  compressing  force  used  to  effect  the  liquefaction  of  carbonic  acid  is  that  of  the 
elasticity  of  the  gas  itself.  The  experiment  may  be  performed  by  generating  carbonic 
acid  in  a  closed  glass  tube,  as  has  been  previously  explained  (see  §  ITS) ;  but  usually  an 
apparatus  constructed  for  this  particular  purpose  is  employed.  This  consists  of  two  cyl- 
indrical vessels,  Fig.  152,  each  of  wrought  iron,  and  each  sufficiently  strong  to  withstand 

Fia.  152. 


a  pressure  of  4,000  Ibs.  per  square  inch.  One  of  these  vessels  serves  as  a  generator,  and 
the  other  as  a  receiver,  and  both  are  furnished  with  stop-cocks  of  a  peculiar  construction. 
The  generator  is  furnished  with  an  axis,  and  is  mounted  upon  an  iron  frame,  so  that  it 
may  revolve  in  a  vertical  plane.  The  receiver  is  supplied  with  a  tube,  which  goes  nearly 
to  the  bottom,  and  the  generator  with  a  cylindrical  copper  vessel  which  admits  of  being 
filled  with  oil  of  vitriol. 

The  operation  is  conducted  by  charging  the  generator  with  a  solution  of  bi-carbonate 
of  soda,  and  the  copper  vessel  with  sulphuric  acid.  The  stop-cock  of  the  generator  being 
now  firmly  closed,  the  generator  itself  is  revolved  upon  its  axis,  by  which  means  the  oil 
of  vitriol  contained  in  the  copper  vessel  runs  out  upon  the  carbonate  of  soda,  and  occa- 
sions a  liberation  of  carbonic  acid.  After  a  time,  when  the  action  is  complete,  the  re- 
ceiver, which  is  immersed  in  a  freezing  mixture,  is  connected  by  means  of  a  metallic  tube 
with  the  generator,  and  the  stop-cocks  being  opened,  the  carbonic  acid  contained  in  the 
generator  rushes  over  into  the  cold  and  empty  receiver,  and  becomes  in  part  condensed. 

QUESTION. — Give  a  general  description  of  the  process. 


294  INORGANIC    CHEMISTRY. 

In  this  condition  it  wastes  away  slowly,  and  may  be  handled  and  molded 
with  ease.  If  suffered  to  remain  in  contact  with  the  skin,  however,  it  burns 
like  a  red-hot  iron. 

"When  a  little  mercury  is  placed  in  a  porcelain  cup  and  covered  with  solid 
carbonic  acid,  the  addition  of  a  few  drops  of  ether  occasions  so  rapid  an 
evaporation  that  the  mercury  is  immediately  frozen,  and  may  then  be  ham- 
mered and  drawn  out  like  lead.  In  this  way  ten  pounds  of  mercury  may  be 
frozen  in  less  than  eight  minutes. 

434.  Lime-water  brought  in  contact  with  carbonic  acid  gas  rapidly  absorbs 
it,  and  becomes  milky  from  the  formation  of  carbonate  of  lime  (chalk).     This 
reaction,  therefore,   constitutes  a  test  for  the  presence   of  carbonic   acid. 
Thus  if  we  expose  fresh  lime- water  to  the  air,  a  pellicle  of  carbonate  of  lime 

soon  forms  upon  its  surface,  proving  the  pres- 
ence of  carbonic  acid  in  the  atmosphere.  In 
like  manner,  by  blowing  through  a  tube  (see 
Fig.  153)  into  a  vessel  of  lime-water,  we  can 
demonstrate  the  abundant  presence  of  carbonic 
acid  in  the  air  expelled  from  the  lungs.  The 
milkmess  occasioned  by  the  contact  of  car- 
bonic acid  with  lime-water,  disappears  when 
an  additional  quantity  of  acid  is  taken  up  by 
the  solution — carbonate  of  lime  being  soluble 
hi  an  excess  of  carbonic  acid.  Many  natural 
waters,  by  virtue  of -an  excess  of  carbonic 
acid  contained  in  them,  hold  very  considerable 
quantities  of  lime  in  solution,  and  are  thereby 
rendered  "  hard."  When  such  waters  are  heated  or  agitated  with  air,  a  portion 
of  the  carbonic  acid  escapes,  and  the  lime  is  precipitated — forming  in  boilers 
and  tea-kettles,  and  in  the  channels  of  streams,  incrustations  of  lime. 

435.  Petrifactions . — It  often  happens,  when  an  organic  substance 
is  placed  in  water  holding  lime  in  solution  by  virtue  of  an  excess  of  carbonic 
acid,  or  other  mineral  matter,  that  its  particles,  as  they  decay,  are  replaced 
by  particles  of  mineral  matter,  until  at  last  all  the  organic  particles  disappear, 
and  a  stony  mass  is  substituted,  which  resembles  the  original  substance  in 


The  stop-cocks  are  now  closed,  the  vessels  disconnected,  and  the  generator  opened  and 
freed  of  its  contents.  It  is  then  charged  afresh,  and  the  operation  repeated  as  before  ;  five 
or  six  repetitions  being  necessary  before  any  very  considerable  quantity  of  liquefied  acid 
becomes  accumulated  in  the  receiver. 

The  liquefied  gas  can  be  drawn  off  from  the  receiver  by  means  of  a  jet,  a,  screwed  on 
to  its  stop-cock.  When  a  portion  is  discharged  by  means  of  this  jet  into  a  metallic  box, 
b,  fitted  with  perforated  wooden  handles,  a  part  of  the  liquid  gas  assumes  a  solid  condi- 
tion in  consequence  of  the  intense  cold  developed  by  the  evaporation  of  another  portion, 
and  the  box  becomes  filled  with  a  white  solid,  like  dry  snow. 

QUESTIONS.— What  are  the  properties  of  the  solidified  gas  ?  What  is  a  test  for  the 
presence  of  carbonic  acid?  What  are  illustrations?  Under  what  circumstances  does 
carbonate  of  lime  dissolve  in  water  ?  When  is  it  deposited  ?  What  are  petrifactions  ? 


CARBON.  295 

form  and  structure,  and  not  unfrequently  in  color.  This  result  is  termed 
petrifaction.  It  is  a  mistake,  however,  to  suppose  that  the  original  particles 
are  converted  into  stone ;  for  the  process  of  petrifaction  is  one  of  replace- 
ment, and  not  of  conversion,  i.  c.,  a  particle  of  mineral  matter  of  the  samo 
form  being  substituted  for  each  organic  particle. 

436,  The  presence  of  carbon  in  carbonic  acid  may  be  demonstrated  by  drop- 
ping a  piece  of  ignited  potassium  into  a  small  flask  filled  with  the  dry  gas. 
The  potassium,  by  depriving  the  carbonic  acid  of  its  oxygen  to  form  potash, 
liberates  carbon,  which  is  deposited  in  the  form  of  black  particles  upon  tho 
walls  of  the  glass.     This  experiment,  which  is  a  very  striking  one,  may  also 
be  performed  by  igniting  a  bit  of  potassium  in  a  glass  tube,  through  which 
a  current  of  dry  carbonic  acid  is  at  the  same  time  transmitted. 

437,  Carbonic  acid  is  evolved  from  the  earth  in  many  localities,  particu- 
larly in-volcanic  districts.     At  one  locality  near  Vesuvius  in  Italy,  it  is  esti- 
mated that  600  Ibs.  weight  are  discharged  every  twenty-four  hours. 

438,  The  salts  formed  by  the  union  of  carbonic  acid  with  the  protoxyda 
of  the  metals,  are  numerous  and  important,  and  are  termed  CARBONATES. 
They  are  easily  decomposed  by  contact  with  the  stronger  acids,  and,  with 
the  exception  of  the  carbonates  of  the  alkalies,  they  are  for  the  most  part  in- 
soluble in  water. 

439.  Carbonic  Oxyd,  CO, — When  carbonic  acid  is  passed 
over  red  hot  coal,  or  metallic  iron,  it  loses  half  of  its  oxy- 
gen, and  becomes  converted  into  carbonic  oxyd. 

This  reaction  is  often  witnessed  in  coal  fires.  The  fuel  in  the  lower  part 
of  the  grate,  which  has  free  access  to  air,  generates  by  its  combustion  carbonic 
acid.  This  passing  up  through  the  interior  of  the  fire,  where  the  supply  of 
air  is  limited,  is  deprived  of  half  of  its  oxygen,  and  becomes  carbonic  oxyd, 
while  at  the  same  time  the  carbon  of  the  heated  fuel  which  has  entered  into 
combination  with  the  removed  oxygen  furnishes  another  equal  quantity  of  tho 
same  gas.  On  coming  in  contact  with  the  air  at  the  top  of  the  fire,  tho  car- 
bonic oxyd  ignites,  and  burns  with  a  flickering,  pale-blue  flame.  This  phe- 
nomenon may  be  particularly  noticed  in  a  charcoal  fire,  when  fresh  coal  has 
been  recently  added. 

Carbonic  oxyd  is  a  transparent,  colorless  gas,  which  is  much  more  poison- 
ous than  carbonic  acid ;  and  the  inhalation  of  air  containing  one  two  hun- 
dredths  of  it,  for  any  considerable  length  of  time,  is  said  to  be  fatal.  Carbonic 
oxyd  may  be  obtained  with  facility  by  heating  crystallized  oxalic  acid  with 
five  or  six  times  its  weight  of  concentrated  sulphuric  acid  in  a  glass  retort, 
and  collecting  over  water.  As  thus  prepared,  it  contains  carbonic  acid,  from 
which  it  may  be  separated  by  allowing  the  mixed  gases  to  bubble  through 
milk  of  lime,  or  solution  of  potash. 

QtTESTiONS. — How  may  the  presence  of  carbon  in  carbonic  acid  be  demonstrated  ?  What 
is  said  of  the  natural  production  of  carbonic  acid  ?  What  of  its  salts  ?  What  is  carbonic 
oxyd  ?  What  is  a  familiar  example  of  its  production  ?  What  are  the  properties  of  car- 
boaic  oxyd  ?  How  is  it  prepared  ? 


296  INORGANIC     CHEMISTRY. 

By  generating-  the  carbonic  oxyd  in  the  same  manner  in  a  test  tube  fitted 
Avith  a  perforated  cork  and  jet,  Fig.  154,  the  gas  may  be 
FIG.  154,          ignited  as  it  is  evolved,  and  its  peculiar  blue  flame  ex- 
hibited. 

440,  Carhon  and  Sulphur* 
Bi -Sulphide  of  Carbon,  CS2. — When  frag- 
ments of  sulphur  are  dropped  upon  ignited  charcoal 
contained  in  a  peculiarly  arranged  earthen  retort,  the 
sulphur  in  the  form  of  vapor  unites  with  the  carbon,  and 
the  product  of  the  combination  distilling-  over,  may  be 
condensed,  in  cooled  receivers,  into  a  colorless,  transpa- 
rent liquid — bi-sulphide  of  carbon. 

This  compound  is  highly  volatile  and  inflammable,  and 
is  characterized  by  a  most  foetid  and  peculiar  odor.  It 
possesses  the  power  of  refracting  fight  in  a  remarkable 
manner,  and  as  the  most  ready  solvent  known  of  gutta-percha,  India-rubber, 
and  various  greasy  and  resinous  substances,,  it  is  somewhat  extensively  ap- 
plied to  manufacturing  purposes.  It  also  dissolves  sulphur,  phosphorus,  and 
iodine — these  bodies  being  deposited  again  in  beautiful  crystals,  by  the  evapo- 
ration of  their  solvent. 
441.  Carbon  and  Nitrogen. 

Cyanogen,  NCa  or  Cy , — This  substance,,  which  is  one  of  the  most 
interesting- compounds  of  carbon,  strikingly  resembles  an  element,  and  was  the 
first  compound  body  which  was  distinctly  proved  to  be  capable  of  entering 
into  combination  with  the  elements  hi  a  manner  similar  to  that  in  which  the 
elements  combine  with  each  other. 

This  discovery,  made  in  1814  by  Guy  Lussacy  formed  an  epoch  in  chemical 
science,  and  by  originating  new  views  of  chemical  composition,,  revolution- 
ized the  whole  subject  of  organic  chemistry.  Since  then,  numerous  other 
bodies  have  been  discovered,  which  deport  themselves  in  respect  to  the  ele- 
ments exactly  as  cyanogen  does — or  in  other  words,  as  if  they  themselves 
irere  elements.  Such  compound  bodies  are  known  in  chemistry  as  compound 
or  organic  radicals ; — the  elements  being-  simple  radicals.  (See  §  211.) 

The  name  cyanogen  (blue-producer,  from  the  Greek  nvavo£T  Hue)  is  derived 
from  the  circumstance  that  this  body  forms  an  essential  ingredient  in  the  pig- 
ment, "Prussian  Blue." 

Cyanogen  consists  of  2  equivalents  of  carbon,  and  1  of  nitrogen ;  but  no 
direct  union  of  these  elements  can  be  effected. 

For  experimental  purposes  on  a  small  scale,  it  may  be  obtained  by  heating; 
in  a  small  retort,  or  test  tube  (see  Fig.  155),  the  salt  known  as.  cyanide  of 
mercury,  previously  reduced  to  a  fine  powder,  and  well  dried.  The  cyanide 


QITESTIONS.— What  is  bisulphide  of  carbon?  What  is  its  method  of  preparation f 
What  are  its  properties?  What  its  practical  applications?  What  is  said  of  cyanogen  ? 
What  are  compound  or  organic  radicals  ?  What  in  chemistry  is  understood  by  a  radical? 
What  is  the  chemical  constitution  of  cyanogen  ?  How  may  it  be  prepared? 


CARBON,  297 

Undergoes  decomposition,  like  the  oxyd  of  mercury  under         FIG*  155* 
the  same  circumstances  (§  281),  yielding  metallic  mer- 
cury and  gaseous  cyanogen,  which  should  be  collected 
over  mercury, 

442.  Properties  .-^Cyanogen  is  a  transparent,  col- 
orless  gas,  with  a  pungent,  peculiar  odorj  somewhat  resem* 
bling  that  of  peach  kernels  f  it  is  nearly  twice  as  heavy 
as  atmospheric  air,  and  when  inhaled,  is  poisonous.  It  is 
inflammable,  and  burns  with  a  beautiful  and  character- 
istic purple  flame.  At  a  temperature  «-~-4°  F.,  it  liquefies, 
and  forms  a  colorless,  limpid  liquid,  which  freezes  at 
•^-30°  F,  into  a  transparent  solid, 

Cyanogen  in  many  of  its  properties  closely  resembles 
chlorine,  and  like  it  unites  with  hydrogen  to  form  an 
&(^id,  and  With  the  metals  to  form  salts,  termed  cyanides, 
wilich  latter  possess  the  characteristic  properties  of  the  haloid  salts, 
/"'443,  Ferrocyanide  of  Potassium,  K2)  F  e  C  y3  -{-  H  0  ,  — * 
'Prussiaie  of  Potash.-^The  compounds  Of  cyanogen  are  almost  always  obtained 
from  a  salt  known  as  ferrocyanide  of  potassium,  or  yellow  prussiate  of  potash, 
which  is  a  double  cyanide  of  potassium  and  iron,  This  salt  is  prepared  on  a> 
large  scale,  by  heating  in  a  covered  iron  pot  or  retort,  about  5  parts  of  refuse 
animal  matter,  such  as  the  parings  of  hoofs,  horns,  hides,  dried  blood,  etc., 
With  2  parts  of  carbonate  of  potash  (pearlash),  and  iron  filings,  At  a  high 
temperature  the  nitrogen  and  carbon  of  the  animal  substances  react  upon 
each  other,  and  form  cyanogen,  Which  combines  With  potassium  derived  from 
the  potash,  and  with  iron.  On  digesting  the  mass,  when  cold,  with  water, 
the  ferrocyanido  of  potassium  (Ks,  Fe  Cft-{-3  HO)  is  formed,  and  may  be  ob- 
tained, by  filtering  and  evaporating  the  solution,  in  splendid,  yellow,  flat 
crystals.  In  this  condition  it  forms  an  important  article  of  commerce. 

444.  Prussian  Blue  .—When  a  solution  of  ferrocyanide  of  potassium 
is  added  to  a  solution  of  peroxyd  of  iron,*  a  beautiful,  deep*blue,  bulky  pre- 
cipitate is  obtained,  which,  when  washed  and  dried,  constitutes  the  well- 
known  pigment,  Prussian,  of  Berlin  blue-^so  called  from  its  discovery  at 
Berlin,  in  Prussia,  in  1710.  This  substance  is  largely  Used  in  painting,  in 
calico-printing,  and  dyeing,  in  staining  wood  and  paper,  and  for*  concealing  of 
neutralizing  the  yellow  color  of  linen  (an  operation  termed  blueing).  Cloth 
may  be  dyed  blue  by  first  immersing  it  in  a  solution  of  peroxyd  of  iron,  and 
then  in  one  of  ferrocyanide  of  potassium  |  the  two  substances  thus  meeting 
in  the  structure  of  the  cloth,  precipitate  or  produce  the  color1  hi  the  very  in- 
terior of  the  fibers. 


*  A  solution  of  pefoxyd  ofiroti  may  be  Readily  obtained  by  dissolving  a  feW  Crystals  of 
copperas  (green  vitriol)  in  water,  adding  a  little  nitric  acid,  and  heating  the  solution. 


.  —  What  are  its  properties?  What  is  said  of  its  affinities  and  Compounds? 
What  is  ferrocyanide  of  potassium  ?  How  is  it  prepared  ?  How  is  Prussian  blue  pre- 
pared ?  What  are  its  uses  ?  How  is  cloth  dyed  of  this  color  ? 


298  INOKGANIC    CHEMISTKY. 

445.  Blue  Ink  .—"-Prussian  blue  is  insoluble  in  water  and  in  dilute  acids, 
With  the  exception  of  oxalic  acid.  The  blue  liquid  obtained  from  its  solution 
in  this  acid,  thickened  with  gum,  constitutes  the  well-known  blue  ink,  or 
writing  fluid. 

The  color  of  Prussian  blue  is  not  Very  permanent,  and  is  instantly  destroyed 
by  the  action  of  the  alkalies,  The  substance  itself  is  formed  by  the  union 
of  cyanogen  with  iron;  and  its  composition,  which  is  somewhat  complex, 
may  be  represented  by  the  formula  (3  Fe  Cy^2  Fe<j  Cys),  Although  con- 
taming  cyanogen,  a  poison,  Prussian  blue  is  not  poisonous,  and  is  used  by 
the  Chinese  in  large  quantities  for  the  coloration  of  "  green  tea.';* 

"When  ferrocyanide  of  potassium  is  added  to  a  solution  of  protoxyd  of  iron 
(green  Vitriol),  it  occasions  a  greenish-white  precipitate,  which,  by  exposure 
to  air,  rapidly  becomes  blue, 

jff /^  erridcyanide  of  Potassium  .—'When  chlorine  gag  is  passed 
through  a  solution  of  ferrocyanide  of  potassium,  a  salt  crystallizing  in  ruby  red 
crystals  is  obtained,  which  contains  a  larger  proportion  of  cyanogen  than  the 
ferrocyanide  of  potassium ;  and  is  known  as  the  ferridcyanide  of  potassium, 
or  the  red  Prussiate  of  potash.  "When  added  to  a  solution  of  the  protoxyd  of 
iron,  it  produces  a  dark-blue  precipitate,  but  with  solutions  of  the  peroxyd  it 
forms  no  precipitate,  By  the  use,  therefore,  of  the  ferro  and  ferrid  cyanides 
of  potassium,  chemists  are  easily  able  to  distinguish  between  salts  of  the  per- 
oxyd and  salts  of  the  protoxyd  of  iron, 

446.  Cyanide   of  Potassium,    KCy.— When   8   parts  of  ferro- 
cyanide of  potassium,  3  of  carbonate  of  potash,  and  1  of  charcoal,  are  exposed 
to  a  strong  red-heat  in  an  iron  crucible,  a  compound  of  cyanogen  and  potas- 
sium is  obtained— the  cyanide  of  potassium.     This  salt,  when  pure,  somewhat 
resembles  white  porcelain  in  appearance ;  it  is  freely  soluble  in  water,  and 
When  taken  into  the  stomach,  is  a  deadly  poison.     The  hands  of  the  work- 
men who  use  this  salt  are  also  liable  to  ulceration. 

The  solution  of  cyanide  of  potassium  in  water  possesses  the  property  of  dis- 
solving most  of  the  metallic  oxyds,  especially  those  of  the  precious  metals ;  it 
is,  on  this  account,  therefore,  extensively  used  for  the  preparation  of  the  gold 
and  silver  solutions  employed  in  electro-gilding  and  plating.  A  solution  of 
cyanide  of  potassium  will  dissolve  out  the  black  marks  of  "indelible  ink," 
which  is  a  solution  of  the  oxyd  of  silver, 

447,  Hydrocyanic  Acid,  HCy,  —  Pruseic  Acid.—  This 
compound,  so  remarkable  for  its  poisonous  properties,  is 

*  The  progress  of  chemical  science  is  strikingly  illustrated  by  the  fluctuations  in  the 
price  of  this  pigment ;— thus  in  17TO,  its  price  was  $10  perpound  ;  in  1815,  $3;  in  1825, 
60  cents ;  and  at  the  present  time,  about  30  cents. 

QiflEStiONS.— -What  is  blue  ink  ?  What  is  said  of  the  permanency  of  the  color  of  Prus- 
sian blue  ?  What  is  its  composition  ?  What  is  the  reaction  of  ferrocyanide  of  potassium 
and  protoxyd  of  iron  ?  What  is  ferridcyanide  of  potassium  ?  What  are  its  reactions  with 
the  solutions  of  the  oxyds  of  iron  ?  How  is  cyanide  of  potassium  formed  ?  What  are  its 
properties  ?  What  its  practical  applications  ?  What  is  said  of  the  formation  of  prussic  acid  ? 


CARBON.  299 

formed  by  the  indirect  union  of  cyanogen  and  hydrogen. 
It  is  easily  obtained  by  distilling  cyanide  of  potassium 
with  dilute  sulphuric  acid. 

The  reaction  is  similar  to  that  involved  in  the  production  of  hydrochloric 
acid  from  common  salt  and  sulphuric  acid  (§  358),  thus: — 

Cyanide  of  potassium.        Sulph.  acid.  Sulph.  potash.          Hydrocyanic  acid. 

KCy      -f      S03,  HO      =-      ^KO,  S03      +    HCy. 

In  its  pure  state,  hydrocyanic  acid  is  a  colorless,  transparent  liquid,  with  a 
feeble  acid  reaction.  It  is  lighter  than  water,  and  so  extremely  volatile,  that; 
if  a  drop  be  allowed  to  fall  upon  a  glass  plate,  a  part  of  the  acid  will  be  frozen 
by  its  own  evaporation.  Its  vapor  has  an  odor  of  peach-blossoms  or  bitter 
almonds,  and  both  of  these  substances  owe  their  peculiar  flavor  in  part  to  tho 
presence  of  this  acid  in  their  composition. 

Hydrocyanic  acid  is  the  most  fatal  of  all  the  poisons  known  to  the  chemist. 
A  single  drop  of  the  concentrated  acid  upon  the  tongue  of  a  large  dog  pro- 
duces immediate  death ;  and  a  slight  inhalation  of  its  vapor  occasions  very 
disagreeable  sensations.  When  largely  diluted  with  water,  it  is  sometimes 
given  in  medicine  in  very  minute  doses.  Ammonia,  brandy,  and  chlorino 
are  its  best  antidotes.  A  suspension  of  animation  occasioned  by  an  over-dosa 
of  it  does  not  always  result  in  death,  if  proper  remedies  are  employed. 

Physiologists  are  not  fully  agreed  as  to  the  cause  of  the  almost  instantan- 
eous death  occasioned  by  this  acid.  By  some  it  is  supposed  to  act  upon  the 
vital  organs  by  reason  of  a  sympathetic  shock  transmitted  to  the  nerves ;  and 
by  others  the  effect  is  ascribed  to  an  almost  immediate  absorption  of  the  poison 
into  the  system. 

Various  parts  of  many  plants  belonging  to  the  order  Eosacece,  such  as  bitter 
almonds,  the  kernels  of  plums  and  peaches,  the  leaves  of  tho  cherry-laurel, 
etc.,  yield,  on  distillation  with  water,  a  sweet-smelling  liquid  containing  hy- 
drocyanic acid. 

448.  Cyanogen  and  Oxygen , — Cyanogen  further  resembles  an 
element  in  the  circumstance  that  it  is  capable  of  uniting  with  oxygen,  in  sev- 
eral proportions,  to  form  acids,  which,  in  turn,  unite  with  bases  to  produce 
salts.  The  two  best  known  of  these  oxyds,  cyanic  and  fulmiuic  acids,  have 
an  identity  of  chemical  constitution,  but  entirely  different  properties. 
/  449.  Cyanic  A  c  i  d  >  C  y  0  is  a  highly  volatile  liquid,  which  decomposes 
quietly,  but  so  readily,  that  it  is  exceedingly  difficult  to  preserve  it  in  unal- 
tered condition ;  its  salts  are  termed  cyanates. 

450.  F  u  1  m  i  n  i  c  Acid,  C  y2  0$,  which,  like  cyanic  acid,  is  composed 
of  equal  atoms  of  cyanogen  and  oxygen,  is  not  known  in  a  separate  state.  Its 
compounds  with  tho  metallic  oxyds  are  termed  fulminates,  since  they  explode, 

QUESTIONS. — "What  chemical  reaction  is  involved  in  its  preparation  ?  What  are  the  pro- 
perties of  prussic  acid  ?  What  is  said  of  its  poisonous  qualities  ?  What  are  its  antidotes? 
How  is  it  supposed  to  occasion  death?  From  what  vegetable  productions  may  prussia 
acid  be  obtained?  In  what  other  respects  does  cyanogen  resemble  an  element?  What 
is  said  of  cyanic  acid?  What  of  fulrninic  »dd? 


800  INORGANIC    CHEMISTRY. 

from  the  slightest  disturbing-  causes,  with  fearful  violence.  The  compound 
with  mercury,  termed  u  fulminating  mercur}^"  is  prepared  by  dissolving  1 
part  of  mercury  in  12  parts  of  nitric  acidr  and  mixing  the  solution  with  an 
equal  quantity  of  alcohol ;  on  the  application  of  gentle  heatr  chemical  action 
ensues^  accompanied  by  the  evolution  of  copious  white  fumes,  and  the  fulmin- 
ate separates  in  white  crystalline  grains.  As  thus  obtained,  it  constitutes, 
when  mixed  with  six  times  its  weight  of  saltpeter,  and  made  into  a  paste 
with  water,  the  composition  used  for  filling  percussion  caps.^x 

Besides  the  fulminate  of  mercury,  analagous  compounds  may  be  formed  in 
a  similar  manner  with  oxyds  of  silver,  copper,  zinc,  and  other  of  the  elements. 
All  of  them  are  exceedingly  dangerous  to  handle,  and  the  fulminate  of  silver 
ranks  next  to  the  chloride  of  nitrogen  in  explosive  character;  thus,  it  explodes 
under  water  when  heated  to  212°  F.,  and  also  when  in  a  moist  state  Tby  fric- 
tion with  a  hard  body  ;  when  dry,  the  touch  of  a  feather,  or  the  vibration  of 
the  house  occasioned  by  the  rolling  of  a  carriage,  is  also  sufficient  to  cause  its 
violent  decomposition.  The  fulminic  acid  separates,  on  exploding,  into  nitro- 
gen, carbonic  oxyd,  and  the  vapor  of  water,  the  metal  being-  set  free.* 

451.  Compounds  of  Carbon  and  Hydrogen, — The  com- 
pounds of  carbon  with  hydrogen  are  numerous,  and  are 
all  derived  from  the  decomposition  of  bodies  of  an  or- 
ganic origin.  Some  of  these  are  liquid,  some  solid,  and 
others  are  gaseous. 

The  consideration  of  two  of  them  only  properly  pertains  to  the  department 
of  inorganic  chemistry.  These  are,  light  carburetted  hydrogen  gas,  C2Il4,  and 
heavy  carburetted  hydrogen,  or  Olefiant  gas,  Gill*. 

452.  Light  Carburetted  Hydrogen,  CsEt, — Marsh  Gas ; Fire- 
damp.— This  gas  occurs  abundantly  in  nature.  It  is  evolved  from  rock-fissures 
in  coal  mines,  and  forms,  in  connection  with  atmospheric  air,  an  explosive 
compound,  known  to  the  miners  as  "  fire-damp/rf  It  is  also  a  constant  product 
of  the  putrefactive  decomposition  of  wood  and  other  carbonaceous  "bodies  un- 
der water,  and  may  be  obtained  from  this  source  by  stirring  the  mud  at  the 
bottom  of  stagnant  pools,  and  collecting  the  gas  as  it  rises  by  means  of  an 
inverted  bottle  and  tunnel.  (See  Fig.  155.)  At  Kanawha,  in  Virginia,  this 
gas  rises  in  immense  quantities  in  connection  with  salt-water  from  Artesian 


*  The  detonating  bombs  with  which  the  life  of  Napoleon  III.  was  attempted  in  1S53, 
were  filled  with  fulminating  mercury. 

t  In  this  condition  it  accumulates  in  the  galleries  of  coal  mines  In  large  quantities,  am! 
when  fired  by  accidental  contact  with  flame,  explodes  with  fearful  violence.  The  product 
of  the-  explosive  combustion  is  mainly  carbonic  acid,  so>  that  the  workmen  In  the  mine  wh<> 
escape  death  by  burning,  are  almost  certain,  to  be  afterward  suffocated.  By  an  explosion 
of  this  character  at  the  Felling  colliery  in  England,  in  1812,  92  persona  lost  their  lives. 
These  accidents:  have  now  been  in  a  great  measure  prevented  by  the  use  &f  the  "  safety 
lamp." 

QUESTIONS. — How  is  fulminating  mercury  prepared  ?  To  what  ase  is  it  applied  ? 
What  is  said  of  the  other  fulminates  ?  What  is  said  of  the  compounds  of  carbon  and  hy- 
drogen 2  What  is  said  of  light  carburetted  hydrogen  2  What  is  "  fire-damp »" 


CARBON. 


301 


FIG.  155. 


wells,  and  being  conducted  by  an  ar- 
rangement of  pipes  under  the  salt- 
boilers,  furnishes  sufficient  heat  by 
its  combustion  to  evaporate  the  brine. 
A  similar  natural  supply  of  this  gas 
in  the  town  of  Fredonia,  in  New 
York,  has  for  many  years  past  been 
extensively  applied  for  illuminating 
purposes. 

453.  Properties . — Light  car- 
buret ted  hydrogen  is  a  colorless,  in- 
odorous, tasteless  gas,  slightly  soluble 
in   water,    and    when    diluted   with 
common  air  may  be  inhaled  with- 
out injury.     Its  weight  is  about  half 
that  of  air.     It  does  not  support  com- 
bustion, but  is  itself  inflammable,  and 
burns  with  a  yellow,  luminous  flame, 

When  mingled  with  air  or  oxygen  gas  it  forms  explosive  compounds.     100 
parts  of  this  gas  by  weight,  consist  of  75  carbon  and  25  hydrogen, 

454.  Heavy  Carburetted  Hydrogen.    Olefiant  Gas,  C4H4, 
— This  gas  was  discovered  in  1796-  by  an  association  of  Dutch  chemists,  who 
gave  it  the  name  of  "olefiant"  (oil -producer),  from  its  formation  with  chlorino 
of  a  compound  having  the  appearance  of  oil.     It  does  not  occur  naturally, 
but  is  obtained  by  the  destructive  distillation*  of  oil,  and  also  in  connection 
with  light  carburetted  hydrogen  and  some  other  substances^  when  coal,  resin, 
tar,  asphaltum,  fat,  animal  refuse,  and  similar  inflammable  matters  are  distilled 
for  the  purpose  of  obtaining- gas  for  artificial  illumination, 

FiG    156  Olefiant  gas  is  easily  prepared  by  heating  to- 

gether 1  measure  of  strong  alcohol  with  2  meas- 
ures of  oil  of  vitriol  in  a  retort  or  flask  capable  of 
holding  at  least  four  times  the  bulk  of  the  liquid 
introduced,     (See  Fig,  156,)     The  gas  comes  off 
freely  at  first,  but  by  degrees  the  mixture  black- 
ens and  froths  up,  so  that  a  careful  regulation  of 
the  heat  is  necessary.     It  is  accompanied  by  tho 
_...  vapor  of  ether,  and  toward  the  close  of  the  pro- 
Si  eess  "by  sulphurous  acid  in  largo  quantities  ?  but 
||^B|  it  may  be  purified  by  causing  it  to  pass,  first 
%fes3|§^H  through  a  "Woulfe's  bottle  containing  a  solution 
~~  ~~  of  potash,  then  through  oil  of  vitriol,,  and  finally 
collecting  over  water, 

*  By  destructive  distillation,  we-  understand  the  decomposition  of  a  body  subjected  to- 
heat  in  a  retort,  accompanied  by  a  partial  or  entire  volatilization  of  Its  products, 

QUESTIONS. — What  are  its  properties  ?    What  is  said  of  olefiant  gas?    How  is  it  ob- 
tained ?      "What  is  understood  by  destructive  distillation  ? 


302  INORGANIC     CHEMISTRY. 

455.  Properties  • — Olefiant  gas,  as  thus  prepared,  is  a  colorless  gas, 
with  a  faint,  sweetish  odor.     It  is  slightly  soluble  in  water,  and  has  about  the 
same  density  as  air.     It  was  liquefied  by  Faraday  under  great  cold  and  pres- 
sure, but  remained  unfrozen  at  — 166°  F. 

Olefiant  gas  does  not  support  life  or  combustion,  but  .is  itself  very  inflam- 
mable, and  burns  with  a  splendid  white  light,  far  surpassing  in  brilliancy 
that  produced  by  light  carburetted  hydrogen.  When  mixed  with  oxygen 
and  fired,  it  explodes  with  great  noise  and  violence.  This  may  be  illustrated 
by  passing  bubbles  of  the  mixed  gases  through  water,  and  igniting  them  at 
the  surface,  care  being  taken  not  to  communicate  fire  to  the  vessel  containing 
the  mixture. 

The  composition  of  defiant  gas  is  2  volumes  of  hydrogen  and  2  of  carbon 
vapor  condensed  into  1  volume. 

When  olefiant  gas  is  mixed  over  water  with  an  equal  volume  of  chlorine, 
the  two  gases  gradually  unite,  and  form  a  heavy,  sweetish,  aromatic  liquid. 
This  substance,  which  collects  in  oily-looking  drops  in  the  water,  is  commonly 
known  as  "  Dutch  liquid,"  from  its  discoverers. 

An  instructive  experiment  may  be  also  performed  by  mixing  in  a  tall  jar  2 
measures  of  chlorine  and  1  of  olefiant  gas.  On  applying  a  light  to  the  mouth 
of  the  vessel,  the  mixture  burns  quietly- — the  chlorine  uniting  with  the  hydro- 
gen to  form  hydrochloric  acid,  while  the  carbon  is  deposited  in  the  form  of  a 
dense  black  smoke. 

456.  Illuminating  Gas,  prepared  by  distilling  in  close 
vessels  bodies  rich  in  hydrogen  and  carbon,  but  deficient 
in  oxygen,  is  always  a  mixture  of  olefiant  gas,  light  car- 
buretted hydrogen,  carbonic  oxyd,  and  hydrogen  in  va- 
riable proportions,  depending  upon  the  nature  of  the  sub- 
stance, and  of  the  process  of  manufacture. 

The  most  valuable  constituent  of  all  illuminating  gases,  is  olefiant  gas ;  and 
if  this  gas  could  be  procured  sufficiently  cheap,  it  would  be  used  alone  in 
preference  to  all  others ;  but  as  this  is  not  the  case,  we  are  obliged,  from  mo- 
tives of  economy,  to  be  content  with  a  mixture  of  olefiant  and  other  gases, 
such  as  is  yielded  by  the  decomposition  of  oils,  fats,  resins,  coals,  and  the  liko 
substances.  Oils  and  fats,  when  distilled,  yield  a  product  very  rich  in  ole- 
fiant gas,  which  has  double  the  illuminating  power  of  the  best  coal  gas,  and 
three  times  that  of  ordinary  coal  gas.  Resins  also  yield  a  highly  illuminating 
gas.  The  first  cost,  however,  of  oil  and  resin  is  so  much  greater  than  that 
of  coal,  that  the  former  are  not  able  in  an  economical  point  of  view,  to  com- 
pete with  the  latter,  although  the  product  of  gas  from  coal  is  every  way  in- 

QTTESTIONS.— What  are  its  properties?  What  is  said  of  the  illuminating  properties  of 
olefiant  gas  ?  What  compound  does  it  form  with  chlorine?  What  phenomena  attend  its 
combustion  with  chlorine  ?  What  is  illuminating  gas  ?  What  is  its  most  valuable  con- 
stituent ?  What  are  the  comparative  values  of  oils,  resins,  and  coals  for  the  manufactura 
of  gas? 


CARBON. 


303 


ferior  to  that  from  oil  and  rosin. 
Thus  a  pound  of  coal  yields  from 
3  to  4  cubic  feet  of  gas ;  a  pound  of 
oil,  15  cubic  feet;  of  tar,  12;  and 
of  resin,  10, 

457.  Coal  G  a  s  is  only  produced 
from  the  bituminous  varieties  of 
coal,  but  all  bituminous  coals  are 
not  fitted  for  gas  manufacture.  The 
production  of  gas  depends  upon  the 
application  of  £  high  temperature  to 
the  coal.  At  a  moderate  heat,  such 
as  400°  F.,  the  volatile  constituents 
of  the  coal  separata  mainly  as  liquids 
• — oil  and  tar*— with  little  or  no  ad- 
mixture of  permanent  gas  j  but  at 
a  cherry-red  heat,  or  a  little  higher, 
there  is  an  abundant  production  of 
gas,  with  only  a  small  production 
of  tar,  etc.  That  variety  of  coal 
known  as  "cannel,"  is  far  superior 
to  all  others  for  the  production  of 
gas. 

The  manufacture,  of  coal  gas  is 
divided  into  three  processes,  viz.,  its 
Formation,  purification,  collection 
and  distribution. 

Its  formation  is  always  of*  ,.,...,.„ 
fected  in  semi-cylindrical 
tubes  of  cast-iron,  called  re- 
torts, arranged  in  furnaces, 
as  is  represented  at  II  F, 
Fig.  157.  The  cylinders  are 
closed  at  the  posterior  end, 
and  open  in  front,  each  being 
provided  with  a  door,  which 
:;  made  to  fit  air-tight  by 
ncans  of  screws  and  moist 
:lay.  In  very  extensive 
gas-works  there  are  from 
400  to  500  retorts,  of  which 
from  200  to  300  are  Worked  night  and  day — each  retort  being  charged  with 
about  120  Ibs.  of  coal  every  6  hours.  The  residue  left  in  the  retorts  after  all 

QUESTIONS.-— What  coals  are  used  for  gns  manufacture?  Upon  what  does  the  produc- 
tion of  gas  from  coal  depend  ?  Into  what  three  processes  is  gas  manufacture  divided  ? 
Describe  the  formation  of  coal  gas. 


304 


INOIIGAKIC    CHEMISTRY, 


the  volatile  products  of  the  coal  have  been  evolved,  is  coke,  which  is  raked 
out,  cooled,  and  used  for  fuel.  Jt  is  Worth,  for  heating  purposes,  as  much  or 
more  than  the  coal  originally  was  from  which  it  is  derived,  and,  therefore, 
the  cost  of  the  coal  used  in  the  retorts  is,  theoretically,  nothing,  Fig.  158 
represents  the  manner  of  charging  and  clearing  the  retorts,  and  the  general 
appearance  of  the  furnaces  of  large  gas*works< 

FIG,  158 


The  volatile  products  evolved  by  heat  from  the  coal  are  light  and  heavy 
carburetted  hydrogen,  carbonic  oxyd,  hydrogen,  oily  vapors,  sulphurous  acid, 
sulphuretted  hydrogen,  ammonia,  carbonic  acid,  aqueous  vapor,  nitrogen,  and 
small  quantities  of  many  other  substances.  This  mixture  is  totally  unfit  for 
illuminating  purposes  until  purified,  which  is  accomplished  as  follows:— 

QUESTION.— What  are  the  volatile  products  evolved  from  the  coal? 


CARBON.  305 

The  gases  and  vapors,  as  they  are  evolved  from  the  coal,  flow  out  of  the 
retorts  through  iron  pipes  into  a  receiver  half  filled  with  water,  which  is 
called  the  hydraulic  maiu,  II,  Fig.  157 — the  extremities  of  the  pipes  dipping 
beneath  the  surface  of  the  water,  in  order  to  prevent  the  gas  from  returning 
into  the  retorts  when  the  doors  are  opened.  In  the  hydraulic  main  a  consid- 
erable quantity  of  the  matters  volatilized  with  the  gas  are  deposited,  viz., 
ammonia  and  the  oily  vapors,  which  condense  into  a  black,  semi-liquid  mass, 
known  as  "  coal-tar."  The  gaseous  products,  however,  being  still  hot,  retain 
various  other  matters  in  a  vaporous  state,  which,  unless  separated,  would  in 
cooling  condense  in  distant  parts  of  the  apparatus,  and  stop  up  the  pipes. 
The  hot  gas  is  therefore  made  to  pass  from  the  hydraulic  main  into  large  up- 
right iron  tubes,  surrounded  with  cold  water,  which  are  called  condensers, 
in  which  the  remaining  vapors  condense  into  a  liquid,  and  trickle  down  into 
reservoirs  provided  for  their  reception,  C,  Fig.  157.  From  the  condensers, 
tlie  gas  passes  through  a  cylindrical  vessel,  P,  Fig.  157,  filled  with  cream  of 
lime,  kept  in  a  state  of  constant  agitation  by  means  of  a  wheel,  or  stirrer,  s  s. 
This  lime  removes  the  carbonic  acid,  the  sulphur  compounds,  and  the  re- 
maining ammonia  from  the  gas,  which  is  then  discharged  into  the  gasometer, 
and  is  ready  for  distribution. 

Dry  lime  arranged  upon  a  series  of  shelves,  over  which  the  gas  is  made  to 
pass,  is  also  used  for  purification.  As  the  gas  leaves  the  lime-purifiers,  the 
pqueous  vapor  which  it  always  contains  in  a  greater  or  less  quantity,  takes 
up  mechanically  certain  portions  of  the  lime ;  each  little  particle  being  in- 
closed in  a  microscopic  vesicle  or  bubble  of  vapor,  which  floats  in  the  gas 
with  its  burden  like  a  miniature  balloon.  In  the  combustion  of  the  gas  these 
vesicles  of  vapor  burst,  and  their  inclosed  particles  of  lime  being  liberated, 
occasion  the  sparkling  which  may  be  generally  observed  in  the  flame  of  coal 
gas. 

In  the  beginning  of  the  distillation,  the  olefiant  gas  forms  about  one  fifth 
of  the  entire  volume,  but  toward  the  end  of  the  process,  or  by  too  strong  a 
red-heat,  its  quantity  considerably  diminishes,  while  that  of  hydrogen  increases. 
The  great  bulk  of  ordinary  coal  gas  is  light  carburetted  hydrogen ;  the  gas 
first  given  off  from  good  coals  consisting  of  13  of  olefiant  gas,  82-5  carburetted 
hydrogen,  3 '2  carbonic  oxyd,  and  1-3  nitrogen.  After  the  lapse  of  5  hours 
the  product  consists  of  7  olefiant  gas,  56  carburetted  hydrogen,  11  carbonic 
oxyd,  21 -3  hydrogen,  and  4*7  nitrogen.  The  free  hydrogen  and  carbonic 
oxyd  present  in  coal  gas  give  no  light,  and  are  positively  injurious,  by  dilut- 
ing the  illuminating  gases. 

Gas  is  sold  by  the  cubic  foot,  or  by  the  thousand  cubic  feet ;  and  an  ordi- 
nary gas-flame  is  generally  estimated  to  consume  from  1  to  1£  cubic  feet  per: 
hour. 

458.  Gas  Meters , — Gas  is  measured  by  means  of  a  self-acting  instru- 

QUESTIONB.—  How  is  the  gas  purified  ?  What  proportion  of  coal-gas  is  olefiant  ?  What 
proportion  is  light  carburetted  hydrogen  ?  How  is  gas  sold  ?  How  much  gas  will  an  or- 
dinary burner  consume  in  an  hour  ?  How  is  gas  measured  ?  Describe  the  construction 
of  the  meter. 


306  INORGANIC     CHEMISTRY. 

ment  called  a  meter.  Its  principle  of  construction  and  working  may  be  illus- 
trated as  follows :  When  a  number  of  vessels,  of  known  capacity,  are  so 
arranged  that  (without  loss  of  gas  in  the  interval)  one  after  the  other  shall  be 
filled  by  gas  in  passing — and  for  this  purpose,  are  inverted  in  water,  into 
which  the  gas  enters,  as  in  the  case  of  an  ordinary  gasometer — it  follows,  that 
just  as  many  cubic  feet  will  have  passed  as  there  are  vessels  that  have  been 
filled.  If  all  these  vessels  are  attached  to  a  common  axis  and  revolve  with 
it,  as  each  in  succession  fills  and  rises,  the  axis  will  be  turned  once  round, 
thereby  indicating  the  passage  of  4  cubic  feet 
of  gas.  Now,  in  the  ordinary  gas-meter  (seo 
Fig.  159),  instead  of  four  separate  vessels,  there 
is  an  outer,  .cylindrical  case,  A  A,  more  than 
half  filled  with  water,  and  a  cylindrical  drum, 
divided  into  four  compartments.  B  B  B  B,  re- 
volving in  it.  The  gas  enters  into  the  revolv- 
ing inner  drum,  by  a  pipe  at  its  center,  and 
discharges  its  gas  into  the  compartment  which 
may  happen  to  be  over  it,  causing  the  compart- 
ment to  rise,  and  the  drum  to  perform  a  portion 
_  of  a  revolution.  "When  the  compartment  be- 

r  n  comes  entirely  filled,  its  edge,  D,  is  lifted  so  far 

out  of  the  water  that  the  gas  contained  in  it  escapes  (passing  in  the  direction 
of  the  arrows)  into  the  space  between  the  two  drums,  and  is  conveyed  away 
by  a  tube  not  shown  in  the  figure.  The  revolving  drum  is  connected  with 
clock-work,  which  shows  by  an  index  the  number  of  revolutions  made,  and 
the  capacity  of  the  compartments  being  known,  the  quantity  of  the  gas  pass- 
ing through  is  accurately  determined.  The  meter  described  is  known  as  the 
"  wet  meter,"  and  is  the  one  in  most  general  use.  Other  arrangements  em- 
ployed for  measuring  gas,  dispense  with  the  water,  and  are  termed  "  dry 
meters."* 

459.  Illuminating  gas  of  all  kinds,  when  mixed  with  air  in  certain  propor- 
tions, forms  explosive  mixtures ;  care,  therefore,  should  be  taken,  not  to  enter 
an  apartment  pervaded  with  a  strong  odor  of  gas,  with  a  light,  until  a  thor- 
ough ventilation  has  been  effected. 

*  The  gas-meter,  when  properly  constructed,  is  an  exceedingly  accurate  instrument, 
though  frequent  differences  arise  on  this  subject  between  gas  companies  and  their  custom- 
ers. These  discrepancies,  occurring  between  one  period  of  consumption  and  another,  and 
•which  are  always  attributed  to  the  meter,  arise  most  frequently  from  differences  in  the 
quality  of  the  gas  furnished ;  for  it  is  a  fact  not  sufficiently  known,  that  the  poorer  the 
gas,  the  faster  it  will  flow  through  the  burners ;  and,  though  the  meter  has  registered 
carrectly  the  volume  of  gas  delivered,  it  does  not  follow  that  the  consumer  has  received 
an  equivalent  amount  of  light.  A  desirable  improvement  in  this  direction  would  be  a 
meter  registering  the  time  or  duration  of  light,  rather  than  the  volume  of  gas.  Until  that 
is  accomplished,  gas  companies  have  no  inducement  to  furnish  good  gas.  The  worst  ar- 
ticle with  which  consumers  can  be  satisfied  will  be  more  likely  to  be  manufactured,  since 
it  is  the  cheapest  to  produce,  and  the  dearest  to  sell. 

QUESTION.— What  is  said  of  the  explosive  compounds  of  illuminating  gas  ? 


C  A  K  B  O  N .  30T 

460.  History . — The  fact  that  a  combustible,  illuminating  gas,  is  pro- 
duced during  the  decomposition  of  coal  by  heat,  was  first  noticed  in  1664,  but 
it  is  only  within  the  present  century  that  any  general,  practical  application  of 
this  knowledge  has  been  made.     Gas  was  first  employed  for  street  illumina- 
tion in  London  in  1812,  and  in  Paris  in  1815.     The  majority  of  householders 
in  London  were  opposed  to  its  introduction  into  the  streets  of  that  city,  and 
for  many  years  the  advocates  of  the  use  of  gas  for  general  illumination,  en- 
countered a  great  amount  of  opposition  and  ridicule.* 

461.  Gas  is  manufactured  from  oil,  resins,  grease,  etc.,  by  causing  them  to 
trickle  into  a  retort  containing  fragments  of  coke,  or  bricks  heated  to  redness. 
Decomposition  of  the  oily  substances  immediately  takes  place,  and  the  gas 
evolved  needs  only  to  be  cooled  to  adapt  it  to  immediate  use. 


CHAPTER  VII. 

COMBUSTION. 

462.  History, — Fire,  in  the  opinion  of  the  ancients,  was 
one  of  the  four  elements  of  nature — earth,  air,  and  water 
being  the  other  three. 

This  doctrine  was  generally  received  until  the  middle  of  the  Ifth  century 
(1650),  when  a  new  theory,  accounting  for  the  various  phenomena  of  combus- 
tion, was  proposed  by  Beccher,  an  eminent  German  physician  and  chemist, — 
which  was  afterward,  toward  the  latter  part  of  the  same  century,  still  further 
elaborated  and  explained  by  Stahl,  also  a  German  physician,  and  one  of  the 
most  eminent  scientific  men  of  his  age.  This  theory,  which  remained  undis- 
puted until  after  the  discovery  of  oxygen  in  IT 74,  was  known  as  the  "Phlo- 
gistic Theory." 

It  started  with  the  assumption  that  there  existed  in  nature  a  distinct 
substance,  or  agency,  constituting  the  principle  of  fire,  called  Phlogiston 
(from  the  Greek  <i/loy££b,  to  burn).  Phlogiston,  although  never  isolated,  was 
believed  to  exist  in  all  combustible  bodies,  and  to  constitute  a  part  of  their 


*  At  the  present  time  it  is  estimated  that  6,000,000  tons  of  coal  are  annually  employed 
in  England  for  the  manufacture  of  gas,  and  from  60  to  75  millions  of  dollars  are  expended 
in  its  production.  In  London  alone,  500,000  tons  of  coal  are  annually  used,  producing 
five  thousand  million  cubic  feet  of  gas,  and  yielding  an  amount  of  light  equal  to  that  which 
would  be  evolved  from  the  combustion  of  ten  thousand  million  of  tallow  candles,  of  six 
to  the  pound. 

QUESTIONS.— What  is  said  of  the  history  and  first  introduction  of  gas  ?  How  is  gas 
manufactured  from  oils  and  resins  ?  What  was  the  original  supposition  concerning  fire  ? 
What  theory  succeeded  ?  Explain  the  general  principles  of  the  phlogistic  theory  ? 


308  INORGANIC     CHEMISTRY. 

structure,  and  its  presence  in  such  bodies  was  supposed  to  endow  them  with 
the  property  of  burning.  When  a  body  burned,  phlogiston  was  liberated,  and 
the  light  and  heat  which  accompany  combustion  were  attributed  to  the  rapid- 
ity which  which  the  phlogiston  passed  out.  "When  a  body  was  wanting  in 
phlogiston,  or  had  once  lost  it,  it  ceased  to  be  combustible,  and  was  said  to  be 
dephlogisticated. 

For  example,  according  to  this  theory,  a  lighted  candle  burns  because  it  is 
a  compound  of  candle-matter  and  phlogiston,  which  compound,  in  the  action 
of  burning,  is  decomposed,  and  the  phlogiston,  set  free,  appears,  in  escaping, 
in  its  natural  character,  as  flame.  The  pure,  dephlogisticated  candle-matter 
is  also  liberated,  little  by  little,  as  the  candle  burns  away,  and  when  collected, 
proves  to  be  water  and  carbonic  acid ;  so  that,  according  to  the  phlogistic 
theory,  tallow  should  be  regarded  as  a  compound  of  fire,  with  water  and  car- 
bonic acid.  Furthermore,  "a  stick  of  brimstone  burns  away  with  a  blue 
flame  and  a  suffocating  vapor,  and  the  residue  of  its  combustion  is  sulphurous 
acid.  In  the  language  of  the  phlogistians,  brimstone  is  a  compound  of  two 
things,  sulphurous  acid  and  phlogiston ;  and  when  it  is  suffered  to  bum,  it 
gives  out  its  phlogiston,  or  flame  of  fire,  and  there  remains  its  dephlogisti- 
cated sulphur,  or  sulphurous  acid,  in  the  separated  state.  Phosphorus,  ac- 
cording to  the  same  hypothesis,  contains  a  white,  deliquescent  acid  (§  405) 
and  phlogiston — the  two  so  loosely  united  as  to  be  kindled  or  decomposed  by 
a  little  friction,  or  by  a  slight  elevation  of  tempc-rature ;  when  burned,  it  sheds 
its  phlogiston,  and  the  phosphoric  acid  is  reproduced." 

It  had  been  long  before  observed,  that  the  metals,  with  the  exception  of 
gold  and  silver,  were  changed  into  rust?,  or  "calxes,"  resembling  chalk,  brick 
dust,  or  other  highly- colored  earthy  bodies,*  when  heated  to  a  high  tempera- 
ture in  the  air.  "We  now  know  these  calxes  to  be  simply  oxyds ;  but  the 
phlogistians,  recognizing  the  only  identity  of  this  alteration  of  the  metals  with 
what  is  undergone  by  sulphur,  phosphorus,  or  any  common  combustible  when 
it  is  burnt  in  the  air,  explained  the  change  as  follows :  they  said  that  each 
metal  was  composed  of  its  own  rust,  or  calx,  and  phlogiston,  and  that  when 
it  was  burned  in  the  fire,  it  gave  out  its  fiery  principle,  while  its  ashes  or 
rust  remained."  Thus,  iron  was  composed  of  iron-rust  and  fire  ;  dephlogisti- 
cate  it,  that  is,  burn  it  to  a  cinder,  and  you  have  rust. 

"  Such  bodies  as  wood,  coal,  and  especially  charcoal,  which  give  out  much 
heat,  and  leave  apparently  little  dephlogisticated  matter  when  burnt,  were 
regarded  as  substances  overcharged  with  phlogiston,  and  therefore  capable  of 
imparting  it  largely  to  others.  Now,  it  always  was,  and  still  is,  desirable  to 
transform  ores,  such  as  iron  rust  in  the  various  iron-stones,  into  metals,  such 
as  iron ;  and  it  has  long  been  understood  that  the  best  way  of  doing  so,  con- 
sists in  mingling  those  ores  with  carbon  in  some  form  or  other,  and  heating 
them  in  a  furnace ;  a  thing  but  too  easily  explained  by  the  phlogistic  theory, 
for  the  carbon  had  only  to  pour  its  phlogiston  into  the  ores  to  convert  them 
into  metallic  natures,  solid  and  bright.  In  the  substance  of  silver  and  gold, 


Iron-rust  (oxyd  of  iron),  oxyd  of  lead,  etc. 


COMBUSTION.  309 

however,  the  phlogiston  (fire)  was  so  compacted  and  inherent,  that  nothing 
could  take  it  out  of  them ;  and  hence  they  remained  fixed  in  the  furnace 
under  all  ordinary  circumstances."  WJUUVCM? 

The  phlogiston,  once  liberated  from  a  metal  or  combustible,  could  not,  liko 
the  dephlogisticated  matter — the  phosphoric,  or  sulphurous  acid,  or  the  iron- 
rust — be  caught  and  measured.  In  the  opinion  of  the  ancients,  it  ascended  at 
once  into  a  boundless  space  of  pure  fire,  called  the  "empyrean,"  which  was 
supposed  to  inclose  the  air  as  the  air  inclosed  the  earth  ;  but  according  to  the 
phlogistians,  it  was  no  sooner  liberated  from  a  combustible,  than  it  passed 
into  combination  with  the  surrounding  atmosphere.  It  could  not,  in  their 
opinion,  be  emancipated  from  its  union  with  one  body,  unless  another  was 
ready  to  take  it  without  delay,  and  the  appearance  called  fire,  was  the  almost 
instantaneous  glance  of  phlogiston  in  its  passage  from  one  engagement  to  an- 
other. Hence  the  necessity  of  the  presence  of  air  to  the  continuance  of  com- 
bustion ;  and  hence  Priestley,  when  he  discovered  oxygen,  supposed  it  to  be 
common  air  deprived  of  phlogiston ;  since  it  did  not  bum  of  itself,  but  power- 
fully supported  combustion,  by  reason  of  its  supposed  attraction  for  the  phlo- 
giston contained  in  combustibles.  He  therefore  called  it  dephlogisticated  air. 

Although  the  phlogistic  theory  ingeniously  explained  a  great  variety  of 
phenomena,  there  were  certain  circumstances  connected  with  combustion 
which  could  not  well  be  accounted  for.  Thus  it  was  observed  that  certain 
metals  were  heavier  after  heating  than  before :  ten  grains  or  ounces  of  lead 
weigh  more  than  ten  after  having  been  burnt  to  calx ;  and  ten  ounces  of 
iron  increase  in  weight  by  conversion  into  rust ; — in  other  words,  the  metals 
lead  and  iron,  supposed  to  be  compound  bodies,  gave  off  by  heating,  one  of 
their  ingredients,  phlogiston,  and  were  thereby  converted  into  elements ;  and 
yet  the  product— the  calx — was  heavier  than  the  original  metal ;  whereas,  if 
phlogiston  was  really  a  material  substance,  and  had  escaped  from  the  lead  or 
the  iron,  the  products,  after  heating,  ought  to  have  weighed  less.  This  diffi- 
culty was  explained  by  assuming  that  phlogiston,  alone  of  all  substances,  was 
endowed  with  the  specific  property  of  lightness,  or  levity,  so  that  it  buoyed 
up,  or  made  lighter,  every  body  with  which  it  combined.  "  This  singular 
evasion  of  the  question  of  weight  only  introduced  another  perplexity ;  but  the 
good  old  chemists  were  equal  to  the  emergency.  If  the  calx  or  rust  of  lead, 
or  of  any  other  metal,  became  lighter,  in  common  balance-weight,  by  combin- 
ing with  phlogiston — that  agent  of  positive  levity — how  was  it  that  it  also  be- 
came specifically  heavier  ?  The  calx  was  comparatively  a  light  stone ;  but 
the  lead  into  which  it  was  converted  by  union  with  light  phlogiston,  was  a 
comparatively  heavy  metal ;  a  cubic  inch  of  the  metal  being  twice  as  heavy 
as  a  cubic  inch  of  the  stone.  If  the  particles  of  an  ounce  of  calx  had  buoj^s 
of  fire  attached  to  them,  so  as  at  once  to  change  them  into  particles  of  lead, 
and  to  make  them  lighter  in  the  aggregate,  how  should  such  enlarged  and 
lightened  particles  produce  a  metal  of  so  much  greater  a  specific  gravity  than 
the  unphlogisticated  rust  ?"  To  this  it  was  replied,  "  that  the  phlogisticated 
particles  of  calx  were  not  enlarged,  but  only  lightened ;  the  fiery  particles 
were  not  stuck  on  to  the  calx  ones  like  so  many  vesicles ;  but  they  pene- 


310  INORGANIC     CHEMISTRY. 

trated  them,  and  then  compressed  them,  so  that  a  greater  number  of  the  fire- 
pierced  earthy  particles  (thereby  rendered  metallic)  packed  into  the  same 
space,  and  therefore  the  metal  was  specifically  heavier,  though  absolutely 
lighter,  than  the  calx  from  which  it  was  made."* — BREWSTER. 

463.  Such  is  a  brief  outline  of  the  celebrated  phlogistic  theory  which  dur- 
ing the  greater  part  of  the  last  century  received  the  sanction  and  support  of 
all  the  chemists  and  scientific  men  of  Europe.  The  honor  of  its  overthrow 
and  tho  establishment  of  correct  views,  belongs  to  Lavoisier,  whose  decisive 
experiments  were  instituted  about  the  year  1780. 

He  took  a  glass  flask,  added  to  it  a  certain  known  weight  of  metallic  mer- 
cury, filled  the  flask  with  oxygen  gas  (which  had  been  discovered  some  years 
previously),  and  hermetically  sealed  it.  The  weight  of  the  whole  was  then 
carefully  ascertained.  The  mercury  contained  in  the  flask  was  then  heated 
to  about  600°  R,  at  which  temperature  it  entered  into  combination  with  the 
gas,  and  formed  a  calx,  or  oxyd  of  mercury.  Lavoisier  then  weighed  the 
flask  and  contents,  and  found  that  it  had  gained  nothing  and  lost  nothing ; 
the  phlogiston,  therefore,  if  it  had  been  driven  out  from  the  metallic  mercury, 
still  remained  in  or  incorporated  with  the  flask  and  its  contents. 

The  flask  being  next  carefully  opened,  the  ah*  from  without  was  heard  to 
rush  into  it,  indicating  the  existence  of  a  vacuum  in  its  interior.  The  mer- 
cury, therefore,  had  not  by  heating  imparted  any  thing  to  the  gas  of  the  flask, 
but  had  really  abstracted  something  from  it,  and  when  taken  out  and  weighed 
separately,  was  found  to  have  increased  in  weight.  That  this  increase  in 
weight  was  due  to  the  abstraction  of  oxygen,  and  to  its  incorporation  with 
the  substance  of  the  mercury,  he  further  proved,  by  decomposing  the  calx; 
(or  oxyd)  of  mercury  (formed  in  the  first  experiment)  into  oxygen  gas  and 
metallic  mercury,  by  heating  it  in  a  suitable  apparatus  to  a  temperature  of 
about  900°  F.  The  two  products  being  carefully  collected,  their  joint  weight 
was  found  to  be  the  same  as  that  of  the  calx  of  mercury  employed.  These 


*  "  How  catholic,  elastic,  and  satisfactory  this  venerable  hypothesis  must  have  been. 
It  was  all  wrong,  indeed,  as  a  substantive  doctrine.  In  one  particular  it  was  a  sort  of  re- 
verse of  truth.  It  is  not  the  calxes  (ores  and  rusts)  and  acids  that  are  simple  ;  it  is  not 
the  combustibles  and  metals  that  are  compound ;  it  is  exactly  the  reverse.  Sulphur, 
phosphorus,  carbon,  and  the  combustibles,  on  the  one  hand,  with  lead,  iron,  and  the 
metals  on  the  other,  are  elementary ;  the  respective  acids  and  calxes  of  these  principles 
are  the  compounds.  The  phlogistians  may,  therefore,  be  said  to  have  perceived  the  re- 
lation subsisting  between  these  two  classes  of  bodies  jupside  down,  like  the  figures  in  a 
camera  obscura.  As  to  the  generic  idea  of  phlogiston,  erroneous  though  it  was  and  is, 
it  is  extant  in  science  yet ;  for  it  is  impossible  to  see  wherein  caloric  differs  from  it 
as  a  scientific  conception,  although  elaborated  with  immensely  greater  precision,  except 
that  caloric  is  the  matter  of  heat,  while  phlogiston  is  the  matter  of  fire.  Both  phlogiston 
and  caloric  are  substances  which  have  no  existence  whatever  in  the  external  world ;  they 
have  both  been  convenient,  though  fictitious  representatives  of  natural  realities,  and  they 
have  both  been  eminently  useful  in  standing  for  certain  phenomena  in  their  several  days, 
but  the  lattar  creation  of  the  materializing  tendency  of  unripe  science  is  not  a  whit  better 
in  essence  than  the  former.'1— SEE  DAVID  BBEWSTEK. 

QUESTIONS. — Who  overthrew  the  phlogistic  theory?  By  what  experiments  was  its 
falsity  demonstrated  ? 


COMBUSTION.  311 

experiments,  therefore,  proved  unmistakably  that  the  calx,  or  red  rust  of 
mercury,  was  a  compound  of  oxygen  and  mercury,  and  not  an  element,  as 
had  long  been  supposed ;  and  that  metallic  mercury  was  not  a  compound  of 
its  own  calx  and  the  positively  light  phlogiston,  but  the  real  element. 

Lavoisier  also  burned  phosphorus  in  a  jar  of  oxygen,  and  observed  that 
much  of  the  gas  disappeared,  and  that  the  phosphorus  gained  in  weight ;  and 
that  the  increase  of  the  one  was  in  the  exact  ratio  of  the  decrease  of  the 
other.  Iron  wire,  also,  burned  in  oxygen,  gave  a  result  equal  to  the  weight 
of  the  wire  employed,  plus  the  weight  of  the  oxygen  that  had  disappeared. 

Observing  also  that  the  results  of  combustion  in  atmospheric  air  were  the 
same  in  degree  as  those  in  pure  oxygen,  he  next  investigated  the  nature  of 
air,  and  found  that  it  consisted  in  part,  of  oxygen  which  supported  and  occa- 
sioned combustion,  and  of  another  gas  which  possessed  properties  entirely  op- 
posite, and  which  we  now  know  to  be  nitrogen. 

The  results  of  the  experiments  of  Lavoisier,  therefore,  demonstrated  that 
there  was  no  such  substance  as  phlogiston,  or  the  matter  of  fire ;  and  that 
when  a  body,  compound  or  elementary,  was  burned,  it  did  not  give  oft*  imag- 
inary buoyant  phlogiston,  but  took  in  real  weighty  oxygen. 

Lavoisier  commenced  his  investigations  in  1772,  and  fully  announced  them 
in  1784.  For  eleven  years  he  encountered  the  opposition  of  the  whole  scien- 
tific world,  with  but  a  single  supporter — Laplace,  the  astronomer.  Gradu- 
ally, however,  the  new  doctrines  gained  ground,  and  before  the  close  of  the 
18th  century  were  generally  received.* 

From  this  point  discovery  rapidly  succeeded  discovery,  until  it  became  at 
last  understood  that  oxygen  was  not  only  the  great  agent  in  combustion,  but 
that  the  respiration  of  all  animals,  the  processes  of  vegetation,  and  the  growth, 
sustenance,  and  decay  of  all  organic  beings  were  dependent  upon  it  as  a  con- 
stituent of  the  atmosphere.  The  true  idea  of  a  chemical  element  was  then 
first  arrived  at, — affinity  or  chemical  attraction  was  recognized  as  an  inde- 
pendent force,  and  the  nomenclature  of  chemistry  at  present  in  use  was  es- 
tablished. In  short,  the  whole  science  of  modern  chemistry  may  be  said  to 
date  its  origin  from  the  epoch  of  the  labors  and  investigations  of  Lavoisier.f 

*  The  two  great  chemists  of  that  day  in  England,  Cavendish  and  Priestley,  never,  how- 
ever, abandoned  the  doctrines  of  phlogiston.  The  former,  when  it  became  evident  that 
the  new  theory  of  chemistry  had  won  the  day,  gave  up  the  science  in  disgust ;  the  latter, 
becoming  involved  in  theological  difficulties,  emigrated  to  Pennsylvania,  where  he  after- 
ward died — maintaining  in  his  correspondence  to  the  last,  a  defence  of  his  favorite  theory. 

t  LAVOISIER.— No  attempt  to  sketch  the  history  of  chemistry  can  be  considered  com- 
plete without  some  notice  of  the  life  of  this  celebrated  man.  He  was  the  son  of  a  rich 
merchant  of  Paris,  and  was  born  in  1743.  He  early  devoted  himself  to  the  study  of  chem- 
istry, as  it  was  then  understood,  was  made  a  member  of  the  French  Academy  at  the 
age  of  25,  and  was  put  at  the  head  of  the  national  powder  and  saltpeter  works  at  33.  His 
great  investigations  on  combustion,  the  composition  of  water,  atmospheric  air,  etc.,  were 
carried  on  during  the  years  1772-83,  during  which  period  he  filled  the  office  of  a  receiver, 
or  "  farmer-general"  of  the  public  revenues.  In  1790  he  was  a  prominent  member  of  the 
famous  commission  which  originated  the  French  system  of  weights  and  measures,  now 
generally  recognized  as  the  true  standard  by  most  scientific  men.  His  labors  in  other  de- 
partments of  science  were  also  numerous  and  important.  In  the  common  course  of 


312  INORGANIC    CHEMISTRY. 

464.  Combustion,  in  the  strict  chemical  acceptation  of 
the  term,  is  a  chemical  process  in  which  at  least  two  ele- 
ments enter  into  combination,  producing  heat  and  a  new 
compound. 

Combustion,  in  the  ordinary  sense,  is  the  rapid  chemical 
union  of  oxygen  with  a  combustible  body,  attended  with 
an  evolution  of  light  and  heat. 

Every  species  of  combustion  with  which  we  are  familiarly  acquainted  is 
simply  a  process  of  oxydation ;  but  combustion  may  occur  without  the  pres- 
ence of  oxygen,  or  in  oxygen  without  the  sensible  evolution  of  either  heat  or 
light.  For  example,  when  antimony  in  powder  or  copper  in  the  form  of  thin 
leaf  is  presented  to  chlorine,  a  combination  is  instantly  effected  between  these 
bodies — a  chloride  of  copper  or  antimony  being  produced,  with  an  evolution 
of  vivid  light  and  heat ;  and  on  the  other  hand,  the  decay  of  wood,  or  the  rust 
of  metals  in  air — changes  effected  by  union  of  these  substances  with  oxygen 
— are  true  examples  of  combustion — heat  and  a  new  compound  being  pro- 
duced without  the  evolution  of  light 

465.  All  bodies  may,  with  reference  to  combustion,  be  arranged  under  one 
of  three  classes,  viz.,  supporters  of  combustion,  combustibles,  and  burnt  bodies. 

Supporters  of  Combustion  are  those  bodies  which,  like  oxygen, 
allow  other  substances  to  burn  in  them  freely,  but  which  can  not  themselves, 
in  ordinary  language,  be  set  on  fire.  It  is  usual  to  reckon  five  supporters 
of  combustion,  viz.,  oxygen,  chlorine,  iodine,  bromine  and  fluorine. 

Combustibles  are  bodies  which,  like  charcoal,  actually  burn  when 
sufficiently  heated  in  the  presence  of  a  free  supporter  of  combustion. 

Burnt  bodies  are  those  which  will  neither  burn  themselves  nor  sup- 
port the  combustion  of  others.  They  may  be  made  red  hot,  but  do  not  burn  ; 
sand,  iron-rust,  and  earthy  bodies  are  examples  of  this  kind.  They  are  for 
the  most  part  compounds  that  have  at  some  time  or  other  been  produced 
by  combustion ;  or  in  other  words,  they  are  bodies  which  have  been  already 
burned,  and  are  no  longer  fitted  to  undergo  this  change.  Chemists  further 


events,  it  might  have  been  expected  that  the  latter  years  of  his  life  would  have  been 
passed  amid  the  admiration  and  reverence  which  naturally  wait  upon  the  originator  of  a 
new  system  of  acknowledged  truths.  Such,  however,  was  not  his  fate.  He  was  arrested 
during  the  "reign  of  terror,"  and  thrown  into  prison,  on  the  wretched  charge  of  having, 
in  his  capacity  of  a  public  officer,  authorized  the  adulteration  of  the  tobacco  of  the  Re- 
public. When  brought  before  the  revolutionary  tribunal,  he  asked  for  a  respite  of  a 
few  days,  in  order  to  complete  some  researches,  the  results  of  which,  he  said,  were  im- 
portant for  the  interests  of  humanity.  The  reply  of  the  judge  was,  that  the  Republic 
wanted  no  scientific  men,  and  forthwith  condemned  him  to  the  guillotine,  to  which  he 
was  dragged  the  next  day,  May  8th,  1794,  in  the  52d  year  of  his  age. 

QUESTIONS. — Define  combustion.  Is  oxygen  necessary  for  combustion?  Into  what 
three  classes  may  :ill  bodies  be  divided  in  respect  to  combustion  ?  What  are  supporters 
«f  combustion  ?  What  are  combustibles  ?  What  are  burnt  bodies  ? 


COMBUSTION.  313 

distinguish  and  classify  burnt  bodies  under  the  names  of  acids,  alkalies,  oxyds, 
salts,  etc. — MILLER. 

466.  Combustion    and    Explosion . — Explosion    in    most,    and 
perhaps  all  cases,  is  a  species  of  combustion,  differing  from  ordinary  combus- 
tion simply  in  the  rapidity  of  action ;  thus  in  combustion,  the  combustible 
and  the  supporter  of  combustion  axe  brought  together  by  degrees,  as  in  the 
flame  of  a  candle ;  but  in  an  explosion  the  whole  action  occurs  at  once. 

467.  The  origin  of  the  heat  which  accompanies  combustion  has  not  been 
satisfactorily  accounted  for.     Every  change  in  the  state  of  a  body  we  know- 
is  accompanied  by  a  change  in  temperature ;  but  why  the  union  of  carbon, 
with  oxygen  to  form  a  gas,  or  oxygen  with  hydrogen  to  form  a  vapor,  should 
produce  a  heat  sufficient  to  melt  the  most  refractory  substances,  still  remains 
unexplained. 

468.  In  all  ordinary  cases   of  combustion,   the  heat 
evolved  does  not  depend  upon  the  combustible,  but  upon 
the  amount  of  oxygen  that  enters  into  combination  ;  or 
in  other  words,  that  combustible  will  evolve  the  greatest 
quantity  of  heat  which  is  capable,  with  a  given  weight, 
of  combining  with  the  most  oxygen. 

For  example,  a  pound  of  hydrogen  in  burning  consumes  or  unites  with  8 
pounds  of  oxygon ;  while  a  pound  of  carbon  unites  with  but  2  2-3  pounds 
of  oxygen.  A  given  weight  of  hydrogen  in  burning  will  produce,  therefore, 
three  times  as  much  heat  as  the  same  weight  of  carbon. 

469.  The  quantity  of  heat  which  a  combustible  body 
evolves  in  combining  with  oxygen,  is  the  same,  whether 
the  combustion  tak*es  place  slowly  or  quickly,  provided 
only  that  the  relative  quantities  of  the  combining  bodies 
are  the  same  in  both  instances. 

Thus,  as  much  heat  is  given  out  in  the  decay  (slow  combustion)  of  a  given 
quantity  of  wood  in  the  air,  as  in  its  quick  combustion  in  a  furnace ;  but  in 
the  former  case,  the  heat  is  much  less  intense,  and  often  becomes  insensible, 
because,  during  the  long  time  occupied  in  the  combination  with  oxygen,  the 
greater  part  of  it  is  carried  away  by  conduction. 

The  temperature  required  to  induce  combustion,  or  the  combination  of  any 
substance  with  oxygen,  is  different  not  only  for  different  substances,  but  even 
for  the  same  substance,  according  as  the  combustion  is  to  take  place  rapidly 
or  slowly.  Thus  phosphorus  combines  slowly  with  oxygen,  or  exhibits  slow 
combustion,  at  77°  F.,  but  does  not  enter  into  rapid  combustion  till  raised  to 

QUESTIONS. — What  is  the  difference  between  combustion  and  explosion?  What  is  the 
origin  of  the  heat  evolved  in  combustion  ?  To  what  is  the  heat  evolved  by  the  combus- 
tion of  a  body  proportioned  ?  Illustrate  this  principle.  Is  the  quantity  of  heat  increased 
by  the  rapidity  of  the  combustion  ?  Illustrate  this.  Is  the  temperature  at  which  com- 
bustion occurs  constant  for  the  same  substance  ?  What  are  examples  of  Blow  combustion? 

14 


314  INORGANIC     CHEMISTRY. 

140°  F.  Tallow  thrown  upon  an  iron-plate  not  visibly  red-hot,  melts  and 
FIG.  160.  undergoes  oxydation,  diffusing  a  palo,  lambent  flame,  only  visible 
in  the  dark.  "When  a  coil  of  thin  platinum  wire  is  first  heated 
to  redness,  and  suspended  in  a  glass  containing  a  few  drops  of 
ether  or  alcohol  (see  Fig.  160).  the  vapors  of  these  substances, 
mixed  with  air,  oxydate  upon  the  hot  metallic  surface,  and  sus- 
tain the  wire  at  a  red  heat,  so  long  as  the  supply  of  mixed  vapor 
and  air  is  kept  up,  without  the  occurrence  of  combustion  with 
flame.  The  product  of  the  oxydation  thus  effected,  is  a  pungent, 
irritating  vapor,  which  affects  the  nose  and  eyes  unpleasantly. 

This  experiment  may  be  modified  by  suspending  a  coil  of  thin 
platinum  wire,  or  a  ball  of  spongy  platinum,  over  the  wick  of       FIG.  161. 
a  spirit-lamp,  supplied  with  alcoholic  ether,  (see  Fig.  161);  on 
ijhting  the  lamp,  and  then  blowing  it  out  as  soon  as  the 
metal  appears  red-hot,  slow  combustion  of  the  spirit  vapor 
supplied  by  the  capillary  action  of  the  wick,  will  take  place, 
and  the  platinum  will  continue  to  glow  for  hours. 

470.  In  combustion,  no  loss  whatever  of 
ponderable  matter  occurs — nothing  is  annihil- 
ated j  but  the  products  of  combustion,  when 
collected  and  weighed,  always  exceed  the  weight  of  the 
original  substance  burned,  by  an  amount  equal  to  the 
weight  of  the  oxygen  absorbed  during  combustion. 

The  most  simple  illustrations  of  this  fact  are  obtained  in  the  combustion  of 
those  bodies  which  afford  a  solid  residue.  Thus,  when  two  grains  of  phos- 
phorus are  burned  in  a  measured  volume  of  oxygen  gas,  they  are  found  con- 
verted, after  combustion,  into  a  white  powder  (phosphoric  acid),  which  weighs 
4£  grains,  or  the  phosphorus  acquires  2|  grains  ;  at  the  same  time,  1%  cubic 
inches  of  oxygen  disappear,  which  weigh  exactly  2|-  grains. — GRAHAM. 

471.  The  constituents  of  all  ordinary  combustible  substances — wood,  coal, 
oils,  fats,  etc. — which  give  to  them  their  value  as  fuel,  are  carbon  and  hydro- 
gen.    These  substances  also  contain  some  oxygen ;  but  this  element  contrib- 
utes nothing  whatever  to  their  value  as  fuel,  and  the  larger  the  proportion  of 
oxygen  in  a  combustible,  the  less  adapted  is  it  for  fuel. 

472.  Products   of  Combustion, — When  combustion  takes  place 
with  a  free  supply  of  air,  oxygen  unites  with  the  carbon  of  the  fuel  to  form 
carbonic  acid,  and  with  the  hydrogen  to  form  vapor  of  water.    These  products 
being  volatile,  rise  in  the  atmosphere,  and  disappear,  forming  part  of  the  aerial 
column  that  ascends  from  a  burning  body. 

473.  The  activity  of  combustion  is  greatly  increased  by  increasing  the  num- 

QUESTIOXS. — Is  any  matter  lost  during  combustion  ?  How  may  this  be  illustrated  ? 
What  are  the  valuable  constituents  of  ordinary  combustibles  ?  What  influence  has  oxy- 
gen as  a  constituent  of  fuel  ?  What  are  the  ordinary  products  of  combustion  ?  How  may 
th«  activity  of  combustion  be  increased  ? 


COMBUSTION.  315 

ber  of  particles  of  oxygen  which  are  brought  in  a  given  time  in  contact  with 
the  combustible,  and  by  carrying  away  the  gaseous  products  of  combustion, 
which  are  no  longer  capable  either  of  burning  or  supporting  combustion,  and 
which,  if  allowed  to  accumulate,  would  cut  off  the  supply  of  fresh  oxygen. 
Hence  the  benefit  of  blowing  a  fire,  or  forcing  a  stream  of  fresh  air  upon  it, 
from  a  bellows,  in  order  to  revive  it,  or  increase  its  intensity.  The  influence 
of  a  long  chimney,  in  producing  a  powerful  heat  in  a  furnace  at  its  base,  by 
increasing  the  draft.,  is  similar;  while  the  effects  of  diminishing  the  supply  of 
air,  by  closing  the  damper,  or  shutting  the  door  of  the  ash-pit,  is  seen  in  the 
diminished  temperature,  and  reduced  consumption  of  fuel  which  occurs  under 
such  circumstances. — MILLER. 

474.  The  weight  of  the  air  required  for  the  combustion  of  fuel  far  exceeds 
that  of  the  fuel  itself;  and  as  the  space  occupied  by  a  given  weight  of  air  is 
much  greater  than  that  of  an  equal  weight  of  fuel,  the  bulk  of  the  air  em- 
ployed to  effect  combustion  is  immense.  For  example,  it  requires  11 '45 
pounds  of  air  to  consume  1  pound  of  pure  charcoal ;  and  as  1  pound  of 
air  occupies  about  13  cubic  feet  of  space,  the  pound  of  charcoal  will  require 
for  its  combustion  at  least  150  cubic  feet  of  air.  As  fuel  is  burned,  however, 
a  much  larger  quantity  is  employed ;  thus,  anthracite  coal  requires  theoreti- 
cally 136  cubic  feet  per  pound,  but  in  practice,  under  steam  boilers,  276  cubic 
feet  are  necessary. 

The  amount  of  heat  which  a  pound  of  pure  charcoal  is  capable  of  producing, 
through  its  union  with  oxygen  in  the  process  of  combustion,  is  sufficient  to 
convert  13  pounds  of  water  at  60°  F.  into  steam  at  212°  F.  The  ingenuity 
of  man  can  not  generate  from  the  combustion  of  a  pound  of  coal  a  greater 
amount  of  heat  than  this,  or  when  generated,  compel  it  to  evaporate  a  greater 
quantity  of  water. 

The  quantity  of  heat  which  is  obtained  from  fuel  in  practical  operations, 
falls  very  far  short  of  its  theoretical  value.  In  some  of  the  Cornish  steam- 
engines,  of  England,  which  are  the  best  in  the  world,  it  is  stated  that  the  ut- 
most theoretical  quantity  has  been  rendered  available ;  but  this  statement  is 
doubtful.  Under  ordinaiy  steam-boilers  not  more  than  two  thirds  of  the 
available  heat  is  ever  utilized,  and  in  a  majority  of  cases  the  proportion  does 
not  probably  exceed  one  half. 

The  reason  of  this  loss  of  heat  in  practice,  is  due  mainly  to  two  causes,  viz., 
the  heated  air  escapes  up  the  chimney  before  it  has  surrendered  to  the  boiler 
or  heating  apparatus,  the  full  amount  of  heat  it  is  capable  of  relinquishing ; 
and,  secondly,  through  want  of  a  perfect  combustion,  the  full  amount  of  heat 
is  not  evolved  from  the  fuel  The  remedy  for  the  first  difficulty  is  to  be 
sought  for  in  improved  mechanical  arrangements  of  boiler  and  furnace  ;  the 

QUESTIONS.— How  is  it  benefited  by  blowing  it  ?  Why  is  the  temperature  and  con- 
sumption of  fuel  reduced  by  closing  the  draft?  What  is  said  of  the  amount  of  air  re- 
quired to  produce  combustion  ?  How  much  air  is  absolutely  required  to  burn  a  pound  of 
charcoal  ?  How  much  heat  will  a  pound  of  charcoal  in  burning  evolve  ?  Is  the  largest 
possible  amount  of  heat  from  fuel  ever  wholly  utilized  ?  Why  is  it  in  practice  that  we 
fail  to  utilize  the  full  amount  of  heat  derivable  from  fuel. 


316  INORGANIC     CHEMISTRY. 

remedy  for  the  second  pertains  to  chemistry,  and  is  to  be  found  in  perfecting 
the  supply  of  air,  When  the  supply  of  air  is  insufficient,  carbonic  oxyd  be- 
comes in  great  part  the  resulting  product  of  combustion,  instead  of  carbonic 
acid ;  but  for  the  formation  of  the  first-named  gas,  only  one  half  the  quantity 
of  oxygen  is  required  as  for  the  production  of  carbonic  acid,  so  that  coal  may 
be  dissipated  in  vapor,  and  may  be  apparently  wholly  consumed  by  one  half 
the  amount  of  air  that  is  usually  required  in  an  open  fire,  under  circumstances 
where  the  full  amount  of  heat  is  given  out.  In  such  cases  a  pound  of  char- 
coal, instead  of  emitting  heat  enough  to  convert  13  Ibs.  of  Water  into  steam, 
will  only  give  out  one  fifth  of  the  heat,  and  will  therefore  convert  but  little 
more  than  2£  Ibs.  of  water  into  steam.*  That  so  great  an  amount  of  loss  as 
this  is  ever  practically  experienced,  is  not  probable ;  but  in  all  furnaces  of 
ordinary  construction,  the  waste  of  fuel  from  this  source  is  very  great.  Owing 
to  the  fact  that  carbonic  oxyd  is  a  colorless  gas,  and  as  the  operations  of  the 
furnace  appear  to  go  on  uninterruptedly,  the  loss  of  heat  occasioned -in  this 
manner  is  very  apt  to  remain  unsuspected. 

By  admitting,  in  a  proper  manner,  an  adequate  supply  of  air,  all  the  car- 
bon in  burning  is  converted  into  carbonic  acid,  and  the  maximum  of  heat 
capable  of  being  evolved  from  the  combustion  is  generated. 

475.  Light  of  Combustion, — The  light  emitted  by  burn- 
ing bodies  is  a  direct  consequence  of  the  heat  evolved  in  the 
process  of  combustion.  All  solids  and  liquids  (as  melted 
metals),  when  elevated  to  a  sufficiently  high  temperature, 
(977°  F.),  become  luminous. 

The  color  of  the  light  emitted  from  an  ignited  substance,  depends  upon  the 
degree  of  temperature  to  which  it  has  been  elevated.  As  the  temperature 
rises,  the  colored  rays  appear  in  the  order  of  their  refrangibility ;  first  red, 
then  orange,  yellow,  green,  blue,  indigo,  and  violet  are  emitted  in  succession. 
At  about  2100°  F.,  all  these  colors  are  produced,  and  from  their  admixture, 
white  light  results,  and  the  ignited  body  is  then  said  to  be  "  white-hot." 

In  all  luminous  flames,  the  light  is  emitted  from  solid 
particles  highly  ignited. 

A  flame  containing  no  such  particles  emits  but  a  feeble  light,  even  if  its 
temperature  is  the  highest  possible.  For  example,  the  flame  produced  by 
burning  a  mingled  jet  of  oxygen  and  hydrogen,  although  one  of  the  most  in- 


*  The  great  loss  of  heat  involved  in  the  production  of  carbonic  oxyd,  is  due  not  merely 
to  the  fact  that  carbonic  oxyd  requires  less  oxygen  for  its  formation  than  carbonic 
but  the  former  gas  occupies  twice  the  bulk  of  the  latter,  and,  consequently,  renders  h 
a  greater  amount  of  heat. 

QUESTIONS. — Under  what  circumstances  will  fuel  be  burned  to  the  best  advant 
Upon  what  does  the  light  which  accompanies  combustion  depend  ?   What  relation  is  thei 
between  the  light  of  an  ignited  substance  and  its  temperature  ?    What  is  flame  ? 
what  does  the  luminosity  of  flame  depend?    Illustrate  this. 


COMBUSTION.  317 

tense  sources  of  heat  at  our  command,  is  so  little  luminous  as  to  be  barely 
visible  in  clear  day-light ;  if,  however,  we  introduce  into  it  a  solid  body,  like 
lime,  the  light  becomes  so  augmented  that  the  eye  can  scarcely  support  it. 
"When  phosphorus  is  burned  in  oxygen,  the  light  is  most  dazzling,  but  when 
burned  in  chlorine,  it  is  extremely  feeble  ;  the  reason  for  the  difference  in 
these  two  cases  is,  that  in  the  first  instance  the  product  of  combustion  is 
solid,  non-volatile  phosphoric  acid,  the  particles  of  which,  becoming  highly 
heated  by  the  combustion,  are  highly  luminous ;  in  the  second  case,  the  pro- 
duct of  combustion  is  a  gas,  and  the  heat  which  its  particles  acquire  in  com- 
bustion not  being  sufficient  to  render  them  luminous,  little  or  no  light  is 
evolved. 

476.  Materials  for  Illumination, — The  materials  or- 
dinarily employed  for  effecting  artificial  illumination,  are 
solid  or  liquid  compounds  of  carbon  and  hydrogen — coal, 
oils,  tallow,  etc. — which  are  generically  termed  hydrocar- 
bons. 

By  heat  we  decompose  them  into  gaseous  compounds  of  carbon  and  hydro- 
gen, and  in  this  state  only  are  they  available  for  purposes  of  illumination.  In 
the  combustion  of  these  two  elements  in  the  flame  of  a  candle,  the  oxygen  of 
the  air  combines  with  both,  but  by  reason  of  a  superior  affinity,  it  unites  first 
with  the  hydrogen  to  form  vapor  of  water,  producing,  thereby,  a  most  intense 
heat,  but  an  almost  imperceptible  light.  The  hydrogen,  in  combining  with 
oxygen,  abandons  the  carbon,  which,  being  thus  set  free  in  the  form  of  min- 
ute solid  particles  in  the  midst  of  the  heated  space,  becomes  white-hot,  and 
imparts  luminosity  to  the  flame.  The  moment,  however,  the  incandescent, 
floating  carbon  comes  to  the  edge  of  the  flame,  it  finds  the  oxygen  of  the  air, 
unites  with  it,  and  becomes  converted  into  invisible  gas — carbonic  acid — 
while  its  place  is  immediately  occupied  by  another  particle  of  solid  carbon. 

Between  the  flame  of  a  candle  and  the  flame  of  gas-light  there  is  no  dif- 
ference; in  the  case  of  tbe  candle,  however,  the  gas  is  generated  and  burned 
at  the  same  time  and  place — the  heat  that  produces  it  serving  also  to  inflame 
it.  In  the  case  of  a  gas-light,  on  the  contrary,  the  inflammable  gas  is  dis- 
tilled by  heat  from  the  illuminating  substances  in  close  vessels  in  one  place, 
and  conveyed  by  pipes  to  be  burned  at  a  place  more  or  less  distant  where  the 
illumination  is  required. 

The  fact  that  the  combustion  of  a  candle  generates  gas  of  the  same  nature 
as  that  produced  in  ordinary  gas  manufacture,  may  be  demonstrated  by  intro- 
ducing one  end  of  a  small  tube  of  glass,  p,  Fig.  162,  into  the  interior  of  the 
flame  of  a  large  candle,  when  a  portion  of  the  inflammable  gas  existing  there 
may  be  drawn  off  and  ignited  at  the  upper  extremity  of  the  tube. 

QUESTIONS. — What  are  the  materials  ordinarily  used  for  artificial  illumination?  What 
are  hydrocarbons  ?  In  what  condition  only  are  they  available  for  illuminating  purposes? 
What  takes  place  during  their  combustion  ?  What  difference  is  there  between  the  flame 
of  a  gas-burner  and  that  of  a  candle  ?  How  may  the  production  of  inflammable  gas  in  a 
candle  be  demonstrated  ? 


318 


INORGANIC    CHEMISTRY. 


PIG.  162. 


The  existence  of  solid  particles  in  every  illuminating 
flame  may  be  also  demonstrated  by  introducing  a  cold 
body  into  the  flame,  which  so  interrupts  the  progress 
of  combustion  that  the  solid  particles  are  no  longer 
consumed,  but  are  deposited  as  soot  "When  we  say 
a  lamp  smokes,  we  mean  that  the  carbon  contained 
in  the  flame  is  passing  off  in  an  unconsumed  state. 

477.  Combustion  of  a  Candle. — A  candle 
is  an  ingenious  contrivance  for  supplying  flame  with 
as  much  melted  fat  as  it  can  consume  without  smok- 
ing. It  is  easy  to  conceive  that  it  would  by  no  means 
be  an  impossibility  to  ignite  a  stick  of  wax  or  tallow 
by  itself;  it  would,  however,  be  a  matter  of  difficulty, 
inasmuch  as  the  material  would  melt  away  long  be- 
fore it  could  inflame.  Supposing,  nevertheless,  it  could  be  ignited,  then  a 
larger  amount  of  combustible  would  be  on  fire  than  the  air  could  consume, 
and  a  large,  thick,  smoky  flame  would  result.  By  the  use  of  a  wick,  this  dif- 
ficulty is  avoided. 

"When  the  end  of  the  wick  which  protrudes  from  the  center  of  the  candle 
is  ignited,  it  radiates  sufficient  heat  downward  to  melt  a  portion  of  the  ma- 
terial of  the  candle,  and  form  a  hollow  cup  filled  with  liquid  combustible 
around  the  wick-fibers.  The  spaces  between  the  fibers  of  the  wick,  acting 
like  a  series  of  small  tubes,  convey  the  fluid  fat  by  capillary  attraction  up  to 
the  flame,  where  it  is  decomposed  into  gaseous  compounds  of  hydrogen  and 
carbon. 

478.  Structure  of  Flame.— The  flame  of  every  lamp  or  candle 
consists  of  three  distinct  portions,  or  rather,  cones  concentric  with  one  an- 
other. The  innermost  cone,  a,  Fig.  163,  is  formed  entirely  of 
combustible  gases,  produced  by  the  decomposition  of  the  illu- 
minating material.  This  is  at  a  temperature  below  redness, 
and  is  consequently  non-luminous.  Around  this  is  the  lumin- 
ous cone  (&),  the  flame  proper,  where  the  hydrogen  is  uniting 
with  the  oxygen  of  the  air,  and  the  particles  of  carbon  not 
having  yet  done  so,  are  floating  about  in  an  incandescent  state 
and  radiating  light.  Beyond  the  second  cone  is  another  film, 
or  casing  (c),  where  the  oxygen  of  the  air  unites  with  the  car- 
bon, and  in  a  properly  adjusted  flame  is  entirely  consumed. 
In  the  flame  of  a  gas-jet  the  same  parts  may  be  also  recognized. 
At  the  base  of  every  flame  a  pale  blue  line  of  light  may  be  ob- 
served; at  this  point,  the  supply  of  oxygen  from  the  air  is 
sufficient  to  completely  and  simultaneously  consume  both  the 
hydrogen  and  the  carbon  supplied  from  the  interior  of  the  flame,  and  there 
being  no  solid  carbon  eliminated,  there  is  consequently  but  a  feeble  light 

QUESTIONS.— How  may  the  presence  of  solid  particles  in  a  flame  be  demonstrated  ? 
When  we  say  a  lamp  smokes,  what  is  understood  ?  What  is  the  necessity  of  the  wick  in, 
a  candle  ?  Describe  the  structure  of  the  flame  of  a  candle. 


PIG.  163. 


COMBUSTION.  319 

The  portion  of  wick  within  the  interior  of  a  candle  flame  is  charred  and 
blackened  by  the  heat,  but  not  consumed,  owing  to  the  fact  that  the  burning 
envelop  which  surrounds  it  effectually  cuts  oil'  all  access  of  air,  and  thus 
prevents  combustion.  For  tiie  same  reason,  also,  the  interior  cone  of  com- 
bustible gases,  iu  every  luminous  flame,  remains  uuignited. 

The  tapering  and  conical  form  which  flames  assume,  is  due  to  the  ascending 
currents  of  rarefied  air  which  are  produced  in  the  atmosphere  by  the  heat 
attendant  on  the  combustion. 

479.  That  the  combustion  of  a  candle  is  superficial,  and  that  the  flame  is  a 
film  of  white-hot  vapor,  inclosing  an  interior  portion  which  can  not  burn  for 
want  of  oxygen,  may  be  demonstrated  by  bringing  down  upon  the  flame  a 
piece  of  thin  glass,  so  as  to  make  a  transverse  section  of  the  flame ;  we  shall 
then  observe  a  ring  of  light  surrounding  the  dark  interior  part  of  the  flame. 
This  experiment  may  be  still  better  performed  by  means  of  a  piece  of  fino 

FIG.  164.         wire  gauze.     "When  this  is  brought  down  upon  the  flame 
1  of  a  large  and  steadily  burning  candle,  the  flame  will  bo 

cut  off  where  it  touches  the  gauze,  and  the  exterior  lumin- 
VHHBMk         ous  circle  will  be  well  defined.     (See  Fig.  164.) 
\pjjfa:.';-  ;\  That  no  combustion  can  go  on  in  the  center  of  flame, 

jiffl  may  be  shown  in  various  ways ;  as  for  example,  if  we  ig- 

jn  nite  a  small  quantity  of  strong  alcohol  iu  a  saucer,  and 

Hi  !•  place  a  rod  of  white  wood  across  it  for  a  few  seconds  (seo 

Fig.  165),  it  will  be  found  on  removing  the  stick,  that  it  is  pIO 
burned  or  blackened  at  only  two  points,  viz.,  where  the 
flame  was  in  contact  with  the  air.  The  same  thing  may 
also  be  shown  by  holding  a  match  stick  for  a  few  seconds 
across  the  middle  of  the  flame  of  a  spirit-lamp  with  a  largo 
wick.  If  a  fragment  of  phosphorus  be  placed  in  a  small 
circular  spoon,  ignited,  and  then  introduced  into  the  mid- 
dle of  a  largo  flame,  it  will  be  extinguished,  but  will  be  re- 
kindled the  moment  that  the  spoon  is  withdrawn  from  the  flame. 

480.  In  order  that  a  flame  should  exist,  a  very  high  temperature  is  es- 
sential.    This  is  particularly  the  case  with  the  flames  produced  by  the  com- 
bustion of  the  hydrocarbons ;  and  if  in  any  manner  the  temperature  of  a 
flame   is  reduced   beyond  a   certain  limit,   it  is  immediately  extinguished. 
Thus,  if  a  stout  copper  wire  be  introduced  into  a  flame,  it  will  be  observed 
that  a  dark  space  is  produced  around  it ;  a  second  wire  cools  the  flame  still 
further ;  and  a  small  flame  may  be  completely  extinguished  by  the  cooling 
effect  produced  by  bringing  down  a  coil  of  wire  upon  it.     If  a  fine  wire-gauzo 
be  brought  over  a  flame,  the  inflammable  gases  will  bo  so  far  cooled  by  pass- 
ing through  its  meshes  (their  heat  being  conducted  off),  that  they  no  longer 
continue  in  a  state  of  inflammation.     (See  Fig.  1G4.)     If  the  meshes  are  very 

QUESTIONS. — Why  is  not  the  wick  of  a  candle  consumed  ?  Why  are  flames  tapering 
and  conical?  What  experiments  prove  that  the  flame  of  a  candle  is  superficial?  What 
that  no  combustion  goes  on  in  the  interior  of  the  flame  ?  What  is  essential  to  the  exist- 
ence of  flame?  Illustrate  this  ?  Why  can  not  a  flame  pass  through  a  wire-gauze  ? 


320 


INORGANIC    CHEMISTKY. 


FiG.  166.  fine,  the  conducting  power  of  the  metal  is  sufficient  to 
cool  the  flame  below  the  point  of  ignition,  even  though  the 
wire  itself  may  be  red-hot.  The  inflammable  vapor  which 
passes  through  the  gauze  may,  however,  again  be  kindled 
by  the  direct  application  of  flame. 

These  experiments   are  well  illustrated  with  a  jet  of 
gas  issuing  under  low  pressure.    If  the  gauze  be  held  over 
the  jet  before  it  is  lighted,  and  a  flame        FIG.  1G7. 
applied  above,  it  will  take  fire  there,  but  the  flame  will 
not  pass  through  to  the  gas  below.    (See  Fig.  167,)    If 
we  place  a  piece  of  camphor  on  the  center  of  the  wire- 
gauze,  and   apply  a  flame  below,  the   cam- 
phor will  melt  and  pass  through  the  meshes, 
but  will  burn  only  on  the  under  side.     (See 
Fig.  168.) 

481.    Safety-Lamp.  —  These    facts,    discovered    by 
Sir    Humphrey  Davy,   were   beautifully  applied    by    him    in 
construction  of  the   "-Safety-Lamp,"  which   allows  the 

FIG.  169. 


FIG.  168. 


the 


miner  to  work  in  safety  in  an  atmosphere  pervaded  with  an 
explosive  mixture  of  light  carburetted  hydrogen  (fire-damp, 
see  §  452).  It  consists  merely  of  a  common  oil-lamp,  the 
flame  of  which  is  completely  inclosed  within  a  cylinder  of  wire- 
gauze.  (See  Fig.  169.)  This  completely  arrests  the  passage 
of  the  flame ;  so  that,  although  the  lamp  be  introduced  into  an 
explosive  mixture,  the  flame  wiH  not  pass  through  the  gauze 
to  ignite  it 

482.  Requisites  far  the  Production  of  Arti- 
ficial Light. — The  essential  requisites  for  the 
successful  production  of  artificial  light  by  the 
combustion  of  the  hydrocarbons,  are,  1st.  That 
there  should  be  a  free  supply  of  air  ;  and?  2d. 
That  the  products  of  combustion  should  be  freely  con- 
ducted off. 

These  two  facts  may  be  illustrated  by  placing  a  glass  cylinder  over  a  lighted 
candle,  in  such  a  way  as  to  cut  off  its  connection  with  air  from  below ;  the 
flame,  hi  this  case,  will  be  extinguished  for  want  of  a  free  supply  of  air.  If 
the  cylinder  be  now  closed  at  the  top,  but  held  over  the  candle  in  such  a  way 
that  the  air  can  gam  admittance  from  below,  the  flame  will  also  be  extin- 
guished, since  the  burnt  gases,  the  products  of  combustion,  are  unable  to 
escape,  and  by  their  accumulation,  prevent  combustion.  If  the  cylinder  be 


QUESTIONS — To  what  invention  has  this  principle  been  applied  ?  Describe  the  safety- 
lamp.  What  are  the  essential  requisites  for  the  production  of  artificial  light?  How  may 
these  be  illustrated? 


COMBUSTION. 


321 


170, 


placed  in  such  a  way  that  the  air  can  gain  free 
admittance  below,  and  escape  freely  at  the  top, 
bearing  with  it  the  products  of  combustion  (see 
Fig.  170),  the  candle  will  not  only  continue  to 
burn  uninterruptedly,  but  its  combustion  will  be 
more  perfect,  than  when  it  is  allowed  to  burn 
openly  in  the  air,  The  reason  of  this  is,  that  the 
ascent  of  the  air,  heated  by  the  combustion, 
creates  a  rapid  current  of  fresh  air  from  below  up 
through  the  cylinder— thus  supplying  more  oxy- 
gen within  a  given  time  and  space,  which  occa- 
sions more  perfect  combustion,  and  a  stronger 
illuminating  flame,  Hence  the  benefit  of  sur- 
rounding a  lamp-flame  with  a  glass  chimney,  open  at  the  bottom  and  top, 

If  too  much  air  be  supplied  to  a  flame,  the  inflammable  gases  burn  with  a 
blue  and  feeble  light,  an  effect  which  may  be  seen  by  blowing  upon  a  com- 
mon gas-flame,  or  by  watching  the  exposed  gas-lights  of  shops  upon  a  windy 
night,  In  these  cases,  the  gas  becomes  immediately  mixed  with  the  oxygen 
of  the  air1,  which  bums  up  the  solid  particles  of  carbon  before  they  are  suf- 
ficiently heated  to  afford  light 

The  necessity  of  air"  for  the  support  of  flame,  is  also  strikingly  shown  by  the 
fact,  that  it  is  impossible  to  light  a  lamp  or  candle  with  a  match,  so  long  as 
the  sulphur  on  the  end  of  it  is  burning  freely  j  since  the  sulphurous  vapor 
abstracts  the  oxygen  from  the  air  around  the  wick,  in  order  to  form  sulphur- 
ous acid, 

483,  Argand  Lamps,—  In  an  ordinary 
lamp  or  candle-flame,  the  combustion  goes  on  only 
at  those  points  where  the  air  has  free  access,  viz,, 
upon  the  outside  of  the  flame,  as  is  indicated  by 
the  existence  of  a  dark  central  portion,  If,  how- 
ever, air  be  introduced  into  the  interior  of  the 
flame,  combustion  is  effected  both  at  the  center4 
and  at  the  circumference,  and  the  light  is  increased. 
This  arrangement  is  practically  carried  out  in 
those  lamps  Which  are  fitted  With  hollow  or  cir- 
cular wicks,  and  which  are  known  as  "  Argand'* 
lamps,  from  their  inventor.  In  these,  a  current  of 
air  rushes  up,  through  the  hollow  wick,  into  the 
center  of  the  flame,  as  shown  by  the  central  ar- 
rows, Fig.  171,  causing  it  to  burn  in  the  form  of  a 
hollow  ring,  The  combustion  is  also  made  more 
powerful,  by  surrounding  the  flame  with  a  glass 
chimney,  which  is  usually  made  conical,  or  is 

QUESTIONS.-- What  is  the  effect  of  admitting  too  much  air  to  a  flame  ?  What  is  an 
Argand  lamp  ?  Describe  its  construction  ? 

14* 


171. 


322 


INORGANIC     CHEMISTRY. 


FIG..  172. 


caused  to  contract  at  a  certain  height  above  the  burner,  so  as  to  form  a 
shoulder,  A  E,  in  order  to  deflect  the  ascending  outer  current  of  air,  and 
throw  it  in  upon  the  flame  at  an  angle.  In  this  way  the  temperature  of  the 
separated  carbon  particles  of  the  flame  is  enormously  increased,  and  the 
greatest  quantity  of  light  is  produced,  from  a  given  amount  of  fuel. 

The  effect  of  the  draft  through  the  interior  of  the  wick,  on 
the  combustion  of  the  inflammable  gases,  may  be  readily 
made  apparent  by  closing,  with  a  piece  of  paper,  the  openings 
in  the  base  of  the  lamp,  through  Which  the  air  gains  admis- 
sion. The  flame  will  immediately  become  impaired  in  bril- 
liancy, burning  with  a  red  light,  and  the  evolution  of  much 
smoke, 

In  an  Argand  lamp  we  are  able  to  burn  tho  poorer  and 
cheaper  oils  (those  which  contain  an  excess  of  carbon)  with- 
out the  production  of  smoke ;  inasmuch  as  the  greater  supply 
of  air  effects  the  entire  combustion  of 
carbon;  whereas,  in  an  ordinary  lamp, 
by  reason  of  the  limited  supply  of  air, 
we  can  use  only  the  best  oils,  or  those 
which  contain  a  large  proportion  of  hy- 
drogen. Fig.  172  exhibits  the  external 
construction  of  an  Argand  burner,  and  the  direction  of 
the  currents  of  air. 

FIG.  174.  484.  Berzelius  Spi  r  it-Lamp. —The 
so-called  "Berzelius  Spirit-Lamp"  (see  Fig. 
173)j  employed  in  chemical  laboratories  for 
obtaining  a  degree  of  heat  greater  than  that  ] 
afforded  by  an  ordinary  spirit-lamp,  is  simply  i 
an  Argand  lamp,  fitted  to  burn  alcohol,  andi 
supplied  with  a  metallic  chimney,  in  place 

one  of  glass.  The  standard  to  which  it  is  attached  is  provided 
With  several  rings  of  various  sizes,  for  sustaining  crucibles,  por- 
celain dishes,  etc.,  which  are  to  be  heated. 

485.  The  B  1  o  w  •  P  i  p  G  .—-The  principles  upon  which  the 
blowpipe  operates  are  essentially  the  same  as  those  involved  in 
the  construction  of  the  Argand  lamp;  a  jet  of  air  or  oxygen  is 
thrown  into  the  interior  of  a  flame,  by  which  the  rapidity  of  com- 
bustion IB  increased,  and  the  heat  of  the  flame  powerfully  augmented. 
The  mouth  blow-pipe  consists  essentially  of  a  bent  tube,  gener- 
ally of  brass,  terminating  in  a  fine  uniform  jet.  (See  Fig.  174).  It 
is  usually  also  constructed  with  a  chamber,  or  enlargement  of  the 
tube,  near  it3  small  extremity,  which  serves  to  collect  the  moisture 
which  condenses  -from  the  breath.  "When  the  jet  of  the  blow-pipe 

QTTESTIONS.— What  is  the  effect  of  closing  the  inner  draft  of  this  lamp  ?  How  is  an  Ar- 
pand  lamp  enabled  to  burn  cheap  oil  ?  What  is  a  Berzelius  spirit-lamp  ?  What  is  thg 
theory  of  the  blow-pipe  ?  What  is  the  construction  of  a  blow-pipe  ? 


C  O  M*B  U  S  T  I  O  N  . 


323 


is  inserted  into  the  flame  of  a  candle,  FIG.  1*75. 

and  a  current  of  air  forced  from  it, 

the  flame  loses  its  luminosity,  and  is 

projected   laterally  in  the  form  of  a 

beautiful,  pointed  cone,  in  which  two 

parts  are  distinctly  discernible,  viz.,  a 

small,  blue  interior  cone,  a  5,  arid  a 

larger  exterior  cone  of  a  yellowish 

appearance,  c.     The  different  parts  of 

this  flame  possess  very  different  properties. 

The  blue  cone  is  formed  by  the  admixture  of  air  with  the  combustible 
gases  rising  from  the  wick ;  in  this  part  of  the  flame  the  combustion  is  com- 
plete, and  the  heat  greatest.  In  front  of  the  blue  cone  is  the  luminous  por- 
tion, consisting  of  unburnt  combustible  gases  at  a  high  temperature,  which 
of  course  have  a  powerful  tendency  to  combine  with  oxygen.  If  a  fragment 
of  some  metallic  oxyd,  such  as  oxyd  of  copper,  be  introduced  into  this  part 
of  the  flame,  the  oxyd  will  be  deprived  of  its  oxygen,  in  consequence  of 
the  superior  affinity  of  the  hot  gases  for  this  element,  and  will  be  re- 
duced to  a  metallic  state :  hence  this  portion  of  the  flame  of  the  blow-pipe 
is  termed  the  "  reducing  flame."  At  the  apex,  or  extreme  point  of  the  outer 
flame,  these  effects  are  reversed.  Here  atmospheric  oxygen  at  a  high  tem- 
perature exists,  and  its  tendency  is  to  unite  with  any  substance  with  which 
it  may  be  brought  in  contact.  Hence  if  a  fragment  of  metal,  such  as  lead, 
tin,  copper,  etc.,  be  placed  at  this  point,  it  will  quickly  become  covered  with 
oxyd ;  and  this  spot  is,  therefore,  called  the  "  oxydizing  flame"  of  the  blow- 
pipe. 

The  opposite  actions  of  the  different  portions  of  the  blow-pipe  flame  may- 
be illustrated  by  the  effects  which  they  produce  upon  a  piece  of  flint-glass, 
which  contains  oxyd  of  lead,  united  with  silica.  In  the  reducing  flame  the 
silicate  of  lead  is  partially  decomposed,  .and  the  glass  at  this  point  becomes 
black  and  opaque  from  the  reduction  of  the  oxyd  of  lead  to  the  metallic 
Btate ;  but  by  placing  the  blackened  part  for  a  few  seconds  in  the  oxydizing 
flame,  oxygen  is  again  absorbed  by  the  metal,  and  the  transparency  of  tho 
glass  is  restored. — MILLER. 


FIG.  176. 


So  also  if  we  hold  a  brightly  pol- 
ished cent  over  the  flame  of  a  spirit- 
lamp  (see  Fig.  176)  the  parts  exposed 
to  the  exterior  of  the  flame  will  be- 
come covered  with  an  iridescent 
coating  of  oxyd,  while  those  over  tho 
center  of  the  flame  remain  bright. 
By  moving  the  coin,  after  it  has  be- 
come thoroughly  heated,  to  and  fro 
over  the  flame,  a  very  beautiful  play 


QUESTIONS. — What  is  the  constitution  of  the  blow-pipe  flame?    What  is  the  reducing 
and  what  the  oxydizing  flame  ?    How  may  their  two  actions  b«  illustrated  ? 


324  INORGANIC     CHEMIST  BY. 

of  colors  win  be  observed,  the  metal  being  alternately  converted  into  oxyd, 
and  the  oxyd  into  metal. 

486.  Carbon,  during  the  act  of  combustion,  as  in  an  ordinary  flame,  assumes 
two  consecutive  phases,  viz.,  while  it  is  evolving  heat  and  light  it  is  a  solid, 
but  immediately  after  it  becomes  a  gas.  It  is  this  property  which  renders 
carbon,  of  all  combustible  bodies,  the  most  suitable  for  heating  and  illuminat- 
ing purposes — questions  of  cost  and  convenience  being  set  aside.  Phosphorus 
burns  in  the  ah*  with  a  more  brilliant  light  than  carbon — yet  this  substance 
could  not  be  used  as  an  agent  for  producing  light  and  heat,  since  the  solid 
products  of  its  combustion  remain  solid,  and  being  deposited  on  contiguous 
objects,  soon  smother  the  combustible  beneath  its  own  ashes.  Zinc,  when 
highly  heated,  burns  in  the  air  with  a  brilliant  flame,  but  the  products  of  its 
combustion — white  oxyd  of  zinc — fall  about  the  illuminating  center  in  a  min- 
iature shower.  The  ordinary  product  of  the  combustion  of  carbon,  on  the 
contrary,  is  a  gas,  carbonic  acid,  which  in  virtue  of  its  gaseous  Qualities  es- 
capes into  the  atmosphere,  and  eombustive  action  remains?  unimpeded.  Had, 
however,  the  results  of  its  combustion  been  a  permanent  solid,  "  the.  world 
would  have  been  buried  beneath  a  covering  of  ashes."* 


CHAPTEE    VIII. 

THE     METALLIC     ELEMENTS. 

48T.  History, — OF  the  whole  number  of  elementary 
substances  included  in  the  class  of  metals,  fully  one  half 
are  so  rare,  that  they  are  known  only  to  the  chemist  and 
the  mineralogist ;  of  the  remainder,  some  fourteen  or  fif- 
teen only  admit  of  any  extensive  practical  applications. 
But  eight  metals  were  supposed  to  be  known  to  the  an- 
cients. 

*  There  can  scarcely  be  conceived  a  more-  beautiful  balance  of  po-wers  designed  for  the 
accomplishment  of  a  specific  end,  than  this  fixation  of  carbon  in  a  pure  state,  and  the 
•volatility  of  its  oxygen  compounds;  yet  so- familiar  has  the  result  become  to  ns — so  un- 
noticed by  its  very  perfection — that  an  effort  of  chemical  reasoning  is  required  to  enable 
ns  to  appreciate  it.  The  enormous  cpiantity  of  ponderable,  yet  invisible  carbon  removed 
in  the  draught  of  our  larger  fireplaces  isT  on  its  first  announcement  startling ;  yet  nothing- 
admits  of  more  satisfactory  proof.  Through  an  average  sized  iron  blast  furnace  there 
rushes  hourly  no  less  a  quantity  of  atmospheric  air  than  six  tons,  carrying  off  fifty-six 
iundredths,  or  more  than  half  a  ton  of  carbon  in  the  form  of  carbonic  acid, — FABADAT. 

QUESTIONS. — What  two  phases  does  carbon  assume  in  combustion  ?  Why  is  it  the  most 
suitable  of  all  bodies  for  combustion  ?  Why  could  we  not  use  phosphorus,  as  an  illuminat- 
ing agent  ?  What  is  said  of  the  relative  abundance  of  the  metals  ? 


THE     METALLIC     ELEMENTS.  325 

488.  Properties . — The  metals,  as  a  class,  are  characterized  by  a  pe- 
culiar luster,  termed  metallic ;  a  property  exhibited  in  the  highest  degree  by 
burnished  steel,  and  the  reflecting  surfaces  of  mercury  in  glass  mirrors.  They 
are  also  possessed  of  a  high  degree  of  opacity,  and  are  good  conductors  of  heat 
and  electricity. 

Density . — In  density  the  metals  differ  greatly ;  potassium  and  sodium 
being  lighter  than  water,  while  gold  and  platinum  are  the  most  dense  of  all 
substances,  being  respectively  nineteen  and  twenty-two  times  heavier  than 
an  equal  bulk  of  water. 

Hardness , — Titanium  and  manganese  are  the  hardest  of  the  metals, 
being  harder  than  steel ;  lead  may  be  scratched  by  the  finger-nail ;  potassium 
and  sodium  are  as  soft  as  wax  ;  while  mercury,  at  ordinary  temperatures,  is 
a  liquid. 

Malleability  and  Ductility . — The  most  malleable  of  the  metals 
are  gold,  silver,  copper,  tin,  cadmium,  platinum,  lead,  zinc,  iron,  nickel,  potas- 
sium, sodium,  and  frozen  mercury — in  the  order  given.  These  may  all  bo 
hammered  out  into  plates,  or  even  into  thin  leaves. 

The  same  metals  are  likewise  ductile,  or  may  be  drawn  into  wires,  although 
the  ductility  of  different  metals  is  not  always  proportional  to  their  malleability. 
The  most  ductile  of  the  metals  are  gold,  silver,  platinum,  and  iron. 

In  the  manufacture  of  gold-thread,  by  recently  improved  processes,  gold  in 
combination  with  silver  is  drawn  into  wire,  by  forcing  it  through  smooth 
conical  holes  perforated  in  rubies — so  fine,  that  a  single  ounce  is  made  to 
stretch  over  a  length  of  sixty  miles. 

Tenacity  , — The  tenacity  of  the  metals,  or  the  power  which  they  pos- 
sess of  resisting  tension  without  breaking,  is  determined  by  ascertaining  the 
weight  required  to  break  wires  of  them  having  the  same  diameter.  Iron 
appears  to  possess  this  property  in  the  greatest,  and  lead  in  the  least  degree, 
A  wire  of  iron  7-100ths  of  an  inch  in  diameter,  will  sustain  a  weight  of  444 
Ibs. ;  a  wire  of  copper  of  the  same  diameter,  300  Ibs. ;  of  gold,  137  j  of 
lead,  24. 

The  tenacity  of  metals,  however,  varies  greatly  in  the  same  metal,  with  its 
purity  and  the  method  by  which  it  has  been  wrought.  Recent  experiments, 
made  under  the  direction  of  the  U.  S,  "War  Department,  have  shown  that  tho 
cohesive  strength  of  iron  is  greatly  increased  by  fusing  it  a  number  of  times- 
lip  to  a  certain  point — its  capacity  to  resist  transverse  strains  being  increased 
thereby  sixty  per  cent.  The  tenacity  of  iron  is  closely  dependent  on  its 
density.  Thus  cast-iron,  having  a  density  of  6'900  has  a  tenacity  five  times 
less  than  iron  of  a  density  of  7 '400,  Iron  castings  of  the  greatest  weight, 


QUESTIONS.— What  are  the  leading  characteristics  of  the  metals  f  What  is  said  of  their 
density?  Of  their  hardness  ?  What  metals  are  the  most  malleable  ?  What  most  duc- 
tile? What  are  illustrations  of  the  ductility  of  the  metals?  How  is  the  tenacity  of  a 
metal  determined  ?  What  metals  possess  this  property  in  the  greatest  and  least  degree  ? 
How  may  the  cohesive  strength  of  iron  be  increased  ?  "What  connection  is  there  between 
the  tenacity  of  iron  and  its  density  ? 


326  INORGANIC     CHEMISTRY. 

according  to  their  size,  are  by  far  the  strongest,  and  weighing  them  is  a  ready 
means  of  judging  comparatively  of  their  strength. 

A  corrugated  sheet  of  metal,  or  one  that  is  doubled  into  ridges  and  folds, 
will  resist  a  far  greater  crushing  force  than  a  flat  surface.  In  the  case  of  cop- 
per, the  ratio  of  strength  has  been  proved  to  be  as  great  as  1  to  9. 

Fusibility  . — All  the  metals  admit  of  being  fused  by  the  application 
of  heat,  but  the  temperatures  at  which  they  liquefy  are  very  various.  Mer- 
cury, for  example,  remains  fluid  at  a  temperature  as  low  as  — 39°  F.,  while 
platinum,  iridium,  rhodium,  and  several  others,  require  the  intense  heat  of 
the  voltaic  battery  or  the  oxyhydrogen  blow-pipe  to  effect  their  fusion. 

Welding . — Some  metals  acquire  a  pasty  or  adhesive  state  before  under- 
going complete  fusion,  in  which,  if  two  clean  surfaces  be  presented  to  each 
other,  and  strong  pressure  or  hammering  be  employed,  they  unite  or  weld 
together,  so  as  to  form  one  continuous  mass.  The  metals  which  possess  this 
property  are  iron,  platinum,  palladium,  and  the  metals  of  the  alkalies. 

Volatility . — At  higher  temperatures  than  is  required  for  their  fusion, 
all  the  metals  are  probably  volatile.  Seven  of  the  metals  are  so  volatile  as 
to  admit  of  distillation  from  the  compounds  which  contain  them.  They  aro 
mercury,  arsenic,  tellurium,  cadmium,  zinc,  potassium,  and  sodium.* 

489.  Alloys . — Combinations  of  the  metals  with  metals  are  termed  Al- 
loys, many  of  which  are  most  extensively  used  in  the  arts,  as  brass,  bronze, 
bell-metal,  type-metal,  German  silver,  etc. 

490.  Amalgam  . — When  the  metals  combine  with  mercury,  the  result- 
ing product  is  called  an  amalgam. 

It  is  sometimes  questioned  whether  alloys  are  true  chemical  compounds ; 
but  the  general  opinion  at  the  present  time  is,  that  they  are  mixtures  of  defi- 
nite compounds,  with  an  excess  of  one  or  other  metal.  The  evidence  in 
favor  of  this  view  is,  that  some  definite  compounds  of  the  metals  occur  natu- 
rally ;  and  when  an  alloy  is  formed,  the  specific  gravity  of  the  compound  is 
either  above  or  below  that  of  the  mean  of  the  metals  employed ;  the  fusing  point, 
also,  of  an  alloy  is  generally  much  lower  than  the  mean  of  the  metals  which 
compose  it  This  is  strikingly  shown  in  an  alloy  called  the  "  fusible  metal," 
which  is  composed  of  8  parts  of  bismuth,  5  of  lead,  and  3  of  tin,  and  melts 
at  203°  F. — a  temperature  more  than  200°  below  the  melting  point  of  tin, 
the  most  fusible  of  its  constituents,  and  400°  below  that  of  lead.  Its  low  fu- 
sibility may  be  illustrated  by  melting  a  quantity  of  it  iu  a  paper  crucible. 


*  Beams  of  -wood  suspended  over  copper  smelting  furnaces  have  been  observed  to  be 
pervaded  throughout  their  entire  structure  with  minute  beads  of  metallic  copper — the 
copper  having  been  raised  in  vapor,  and  so  deposited  within  the  fibers  of  the  wood.  Gold 
may  be  seen  to  undergo  volatilization  in  the  focus  of  an  intensely  powerful  burning-glass ; 
and  fine  wires  of  the  most  refractory  metals  may  be  dispersed  in  vapor  by  transmitting  a 
powerful  electric  discharge  through  them. — MILLEB. 

QUESTIONS.— What  effect  has  corrugation  on  the  strength  of  a  metal  ?  What  is  said  of 
the  fusibility  of  the  metals  ?  What  is  welding  ?  What  metals  can  be  welded  ?  What  ia 
said  of  the  volatility  of  the  metals  ?  What  are  alloys  ?  What  are  amalgams  ? 


POTASSIUM.  327 

491.  All  the  metals  have  the  property  of  assuming  the  crystalline  form 
but  it  is  not  always  easy  to  place  them  under  circumstances  favorable  to  their 
doing  so.     Some  of  them  occur  in  nature,  in  a  crystallized  state,  particularly 
gold,  silver,  copper,  bismuth,  and  platinum. 

492.  All  the  metals  are  capable  of  uniting  with  oxygen,  but  they  differ 
greatly  in  their  affinities  for  this  element.     The  greater  number  combine  with 
it  at  all  temperatures,  and  are  reduced  (deoxydized)  with  difficulty.     Others 
on  the  contrary,  like  gold  and  platinum,  can  not  be  made  to  combine  with 
oxygen  directly ;  and  their  oxyds  are  decomposed  at  a  slight  increase  of 
temperature. 

The  metallic  oxyds  differ  greatly  in  their  properties.  Some  of  them  pos- 
sess basic  characters  more  or  less  marked ;  others  will  not  combine  with  either 
acids  or  alkalies ;  while  a  third  class  have  distinctly  acid  properties.  The 
strong  bases  are  all  protoxyds,  containing  single  equivalents  of  metal  and 
oxygen ;  the  peroxyds  are  generally  neutral,  while  the  metallic  acids  contain 
the  largest  quantities  of  oxygen. 

493.  Classification  of  the  Metals, — The  metals  maybe 
arranged  in  four  classes,  viz.  :  1.  The  metals  of  the  alka- 
lies ;  2.  The  metals  of  the  alkaline  earths  ;  3.  The  metals 
of  the  earths  ;  4.  The  heavy  metals,  or  metals  proper. 

The  latter  class  may  bo  again  subdivided,  according  to  the  affinity  of  the 
metals  contained  in  it  for  oxygen,  into  two  groups — the  noble  and  the  com- 
mon metals.  The  former  resist  the  action  of  oxygen,  like  gold,  silver,  etc.  • 
while  the  latter,  like  iron,  lead,  copper,  etc.,  unite  with  it  readily. 


CHAPTER    IX. 

THE  METALS  OF  THE  ALKALIES. 

THE  metals  which  by  oxydation  produce  alkalies  are 
Potassium,  Sodium,  Lithium,  and  a  hypothetical  sub- 
stance, Ammonium,  the  radical  of  Ammonia. 

SECTION    I . 

POTASSIUM. 
fiqitivaknt,  39'2.     Symbol,  K.  (Kalium).     Specific  gravity,  0'8G5. 

494.  History, — Potassium  was  discovered  by  Sir  Hum- 
phrey Davy  in  1807,  who  obtained  it  by  decomposing 

QUESTIONS. — Do  all  the  metals  crystallize  ?  What  is  said  of  the  affinities  of  the  metals 
for  oxygen  ?  What  are  the  characteristics  of  the  metallic  oxyds  ?  How  may  the  metals 
be  classified  ?  What  are  the  noble  metals  ?  When  and  by  whom  was  potassium  discov- 
ered? 


828  INORGANIC    CHEMISTRY. 

hydrate  of  potash  (KG,  HO)  by  the  action  of  a  powerful 
galvanic  battery. 

The  discovery  of  potassium  marks  an  era  in  the  progress  of  chemistry. 
The  alkalies  and  the  alkaline  earths  had  long  been  suspected  to  be  compound 
bodies,  but  up  to  this  period  they  had  resisted  all  attempts  to  decompose 
them.  When  once,  however,  potassium  had  been  separated  from  its  com- 
pounds, and  potash  had  been  proved  to  be  an  oxyd  of  this  metal,  the  de- 
composition of  the  other  alkalies  and  earths,  and  the  discovery,  in  quick  suc- 
cession, of  sodium,  barium,  strontium,  and  calcium,  followed  as  a  necessary 
consequence. 

495.  Distribution ,— Potassium  is  widely  diffused  in  nature,  but  al- 
ways in  combination  with  other  bodies.     Many  of  the  minerals  which  com- 
pose the  crystalline  rocks,  such  as  feldspar,  mica,  etc.,  contain  potash  united 
with  silica — silicate  of  potash.      As  these  rocks  crumble  down  into  soils, 
potash  assumes  a  soluble  form,  and  is  gradually  taken  up  by  plants,  and  ac- 
cumulated in  their  structure.     When  plants  are  burned,  the  potash  thus  ab- 
sorbed constitutes  a  part  of  their  ashes,  and  from  these  nearly  all  our  supplies 
of  this  substance  are  derived.     Potassium  also  exists  in  sea-water,  as  chloride 
of  potassium. 

496.  Preparation . — The  original  method  of  preparing    potassium 
through  the  agency  of  the  galvanic  battery  is  troublesome  and  expensive, 
and  a  new  method  has  been  devised,  which  consists  essentially  in  subjecting 
a  mixture  of  finely  pulverized  charcoal  and  carbonate  of  potash  in  an  iron 
retort  to  an  intense  heat ;  decomposition  of  the  alkali  ensues,  and  the  potas- 
sium distils  over  in  metallic  globules  which  are  collected  in  a  vessel  of 
naptha. 

497.  Properties . — When  a  globule  of  potassium  is  freshly  cut  open, 
it  appears  as  a  brilliant,   silver-white  metal  j  but  the  exposed  surface  in- 
stantly tarnishes  by  contact  with  the  air,  and  in  a  few  minutes  becomes  cov- 
ered with  a  white  coating  of  oxyd  (potash).     At  common  temperatures  it  is 
soft,  and  may  be  molded  like  wax ;  at  32°  F.  it  is  brittle  and  crystalline.     Its 
attraction  for  oxygen  is  so  great,  that  it  can  only  be  preserved  in  a  pure  stato 
in  exhausted  and  sealed  glass  tubes,  or  under  the  surface  of  some  liquid, 
like  naptha,  which  contains  no  oxygen*     At  high  temperatures  it  will  re- 
move oxygen  from  almost  all  bodies  which  contain  this  element,  with  which 
it  is  brought  in  contact     The  powerful  attraction  of  potassium  for  oxygen 
may  be  illustrated  by  throwing  a  small  piece  of  the  metal  upon  the  surface 
of  water,  in  which  case  a  part  of  the  water  is  immediately  decomposed— its 
oxygen  combining  with  the  potassium  to  form  potash,  whilst  the  liberated 
hydrogen,  taking  fire  from  the  heat  evolved,  burns  in  connection  With  a  por- 
tion of  the  volatilized  metal,  with  a  beautiful  rose- red  flame  (see  Fig.  177); 

QUESTIONS.— -What  consequences  followed  the  discovery  of  potassium  ?  What  is  said 
of  its  distribution  ?  From  whence  are  the  chief  supplies  of  potassium  and  its  compounds 
obtained  ?  How  is  potassium  practically  obtained  ?  What  are  its  properties  ?  What  is- 
said  of  its  attraction  for  oxygen?  How  may  this  be  illustrated  ? 


POTASSIUM.  329 

the  potassium  at  the  same  time  fusing,  assumes  the 
spheroidal  state  (§  154),  and  moves  over  the  surface  of 
the  water  with  great  rapidity,  finally  disappearing  with 
an  explosive  burst  of  steam,  as  the  globule  of  melted 
potash,  which  is  formed  by  oxydation,  becomes  suffi- 
ciently cool  to  come  in  contact  with  the  water.  If  this 
experiment,  which  is  one  of  the  most  beautiful  in  chemistry,  be  made  on  a 
vessel  of  water  reddened  with  a  vegetable  color,  the  alkali  produced  changes 
this  color  to  blue  or  green. 

498.  Compounds    of  Potassium. 

Protoxyd  of  Potassium,  Potash,  or  Potassa,  KO. — 
The  only  known  method  of  obtaining  this  oxyd  free  from  water,  is  by  ex- 
posing potassium  to  dry  air,  when  it  oxydates  to  a  fine  white  powder.  If 
once  united  with  water,  no  degree  of  heat  is  sufficient  to  expel  the  water. 

The  potash  of  commerce  and  of  the  laboratory  is  always  a  hydrate  (KO,  HO). 
It  is  prepared  by  dissolving  carbonate  of  potash  in  ten  or  twelve  times  its 
weight  of  water,  in  a  clean  iron  vessel,  and  adding  to  the  boiling  solution  a 
quantity  of  good  quick-lime  equal  in  weight  to  half  the  carbonate  of  potash 
used.  The  lime  should  be  previously  slacked,  made  into  a  cream  with  water, 
and  added  in  small  portions  at  a  time,  so  that  the  liquid  may  be  kept  at  the 
boiling  point.  The  lime  abstracts  the  carbonic  acid  from  the  potash,  and 
^>rms  carbonate  of  lime ;  which,  being  insoluble,  is  precipitated,  leaving  hy- 
drate of  potash  in  solution.  The  clear  solution,  if  properly  prepared,  will  not 
effervesce  on  the  addition  of  hydrochloric  acid,  thus  showing  that  all  the  car- 
bonic acid  has  been  transferred  from  the  potash  to  the  lime.  The  clear  liquor, 
which  is  known  as  solution  of  caustic  potash,  when  drawn  off  by  a  syphon  from 
the  precipitate,  and  evaporated  to  dryness,  yields  a  grayish-white  solid,  with 
a  crystalline  fracture — the  crude  potash  of  commerce.  This,  melted  and  cast 
into  sticks,  constitutes  the  caustic  or  fused  potassa  of  the  shops  (lapis  infer' 
nalis),  and  is  used  in  this  state  by  the  surgeons  as  a  cautery. 

499.  Properties  , — Hydrate  of  potash,  after  fusion,  is  a  hard,  grayish- 
white  substance  ;  very  deliquescent,  and  dissolving  freely  in  water  and  alco- 
hol.    Both  in  the  solid  state  and  in  solution,  it  rapidly  absorbs  carbonic  acid 
from  the  air,  and  must  therefore  be  preserved  in  closely- stopped  bottles. 

Hydrate  of  potash  possesses  in  solution,  the  properties  termed  alkaline,  in 
the  very  highest  degree.  It  neutralizes  the  most  powerful  acids ;  restores  the 
blue  color  to  reddened  litmus,  changes  the  blue  infusion  of  cabbage  into  green, 
but  in  a  short  time  entirely  destroys  these  colors.  It  has  a  peculiar  odor, 
an  acrid  and  disgusting  taste,  characteristic  of  the  alkalies,  and  quickly  de- 
stroys both  animal  and  vegetable  matters ;  for  this  reason,  its  solution  can 
not  be  filtered,  except  through  pounded  glass  or  sand,  and  is  always  best  clar- 
ified by  allowing  the  impurities  to  subside,  and  then  decanting  off  the  clear 

QUESTIONS. — How  may  potash  free  from  water  be  obtained  ?  What  is  the  composition 
of  commercial  potash?  How  is  it  prepared?  What  is  caustic  potassa?  What  are  its 
properties  ? 


330  INOKGANIC     CHEMISTRY. 

liquor.  Hydrate  of  potash,  when  handled,  imparts  to  the  fingers  a  peculiar, 
soapy  feel,  which  is  occasioned  by  a  gradual  solution  of  the  skin  (cuticle). 

The  affinities  of  potassa  when  heated  are  so  powerful  that  but  few  sub- 
stances are  capable  of  resisting  its  action;  those  which  contain  silica  are  decom- 
posed by  it,  and  even  platinum  itself  is  oxydized  by  it.  With  the  fats  and 
fixed  oils  it  forms  soaps,  which  are  true  salts,  composed  of  a  fatty  acid  and  the 
alkaline  base.  Its  applications  also  in  chemistry  and  in  the  arts  are  almost 
innumerable. 

500.  Potassa  is  the  strongest  base  known  in  chemistry;  consequently,  it 
may  be  used  to  effect  the  decomposition  of  almost  every  salt.  This  may  be 
illustrated  by  adding  a  solution  of  potash  to  a  solution  of  either  the  sulphates 
of  iron  (green  vitriol)  or  copper  (blue  vitriol),  in  water ;  the  potash  immedi- 
ately unites  with  the  acid,  and  the  insoluble  metallic  oxyd  is  precipitated 

Potash  is  a  fatal  corrosive  poison. 

501.  Carbonate   of  Potash,  KO,C02,— Pearlaah.  —  This 
important  salt  is  obtained  almost  exclusively  from  the 
ashes  of  land  plants  ;  the  ashes  of  marine  plants,  on  the 
contrary,  contain  soda,  and  but  comparatively  little  potash. 

In  countries  where  wood  is  most  abundant,  as  in  some  parts  of  the  United 
States,  Canada,  Russia,  etc.,  it  is  burned  exclusively  for  the  sake  of  its  ashes. 
These  are  collected,  placed  in  large  tubs  (leach  tubs),  and  treated  with  water ; 
the  water  soaking  through  the  ashes,  dissolves  out  the  potash  salts,  together 
with  various  other  soluble  mineral  substances,  and  is  converted  into  ley ;  this 
when  evaporated  to  dryness,  yields  an  impure  carbonate  of  potash,  which  is 
sold  in  commerce  in  immense  quantities,  under  the  names  of  pot  and  pearl- 
ashes. 

The  weight  of  ashes  furnished  by  different  plants  varies  in  different  species 
and  soils.  Herbaceous  plants  yield  more  than  woody  ones;  and  the  leaves, 
bark,  and  young  shoots  are  the  parts  which  furnish  the  greatest  quantity  of 
alkali.  Potash  does  not  exist  in  plants  in  the  form  of  carbonate,  but  is  accu- 
mulated in  then-  substance  in  combination  with  certain  organic  acids.  Thus, 
potash  in  the  vine  is  combined  with  tartaric  acid,  and  in  the  sorrel  with  ox- 
alic acid.  "When  plants  are  burned,  these  acids  are  destroyed,  and  the  potash, 
uniting  with  carbonic  acid  formed  during  the  combustion,  is  obtained  in  the 
form  of  a  carbonate. 

Carbonate  of  potash  has  strong  alkaline  properties,  and  dissolves  in  about 
twice  its  weight  of  water. 

502.  Bi-Carbonate  of  Potash,   KO,2C02isa  compound  con- 
taining double  the  quantity  of  carbonic  acid  that  ordinary  potash  does  ;  it  is 

».  «~  JL  ^ 

QTIESTIONS.— What  gives  to  potash  its  peculiar  feeling?  What  is  said  of  its  affinities 
and  uses  ?  What  of  its  basic  properties  ?  From  what  source  is  carbonate  of  potash  ob- 
tained ?  What  is  the  process  of  preparing  it  ?  Under  what  name  does  it  occur  in  com- 
merce ?  What  is  said  of  the  amount  of  ash  yielded  by  plants  ?  In  what  state  does  potash 
exist  in  plants  ?  What  is  bi-carbonate  of  potash  ? 


POTASSIUM.  331 

very  generally  known  under  the  name  of  "saleratus,"  but  this  term  is  often 
applied  to  designate  any  purified  carbonate  of  potash. 

503.  Nitrate   of  Potash,  KO,  JV  05.  —  Saltpeter,  Niter.— This  salt 
occurs  somewhat  abundantly  as  a  natural  product.     The  chief  sources  of  its 
supply  are  certain  districts  of  the  East  Indies,  where  it  is  found  disseminated 
through  the  soil,  or  as  an  efflorescence  upon  the  surface.     It  is  obtained  in  a 
separate  state  by  treating  the  earth  with  water,  and  allowing  the  solution  to 
crystallize.     It  is  supposed  to  be  produced  by  the  decomposition  of  organic 
matters  containing  nitrogen  in  soils  containing  potash  and  lime. 

In  Europe  saltpeter  is  formed  artificially  by  mixing  animal  refuse  of  all 
kinds  with  old  mortar,  wood-ashes,  etc.,  in  heaps,  exposed  to  the  air,  but 
sheltered  from  the  rain.  These  heaps  are  watered  from  time  to  time  with 
putrid  urine,  and  after  the  lapse  of  two  or  three  years  the  mixture  is  washed, 
and  the  salt  crystallized  out.  A  cubic  foot  of  refuse  may  in  this  way  be 
made  to  yield  as  much  as  20  ounces  of  niter. 

The  earth  on  the  floor  of  many  caverns,  as  the  Mammoth  Cave  of  Kentucky, 
often  becomes  strongly  impregnated  with  nitrate  of  lime,  which,  when  leached 
with  wood  ashes,  or  treated  with  potash,  is  decomposed,  and  yields  nitrate  of 
potash.  In  this  way  saltpeter  was  manufactured  for  the  Government  during 
the  war  of  18 12. 

504.  Properties . — Saltpeter  crystallizes  in  long,  six-sided  prisms,  and 
is  freely  soluble  in  water ;  its  solubility  increasing  in  a  remarkable  manner 
with  the  temperature  of  the  water;  thus,  100  parts  of  water  at  32°  F.  dissolve 
*l  parts;  at  65°  F.,  29  parts;  and  at  212°  F.,  400  parts.     The  taste  of  salt- 
peter is  cooling  and  saline ;  it  is  an  antiseptic,*  and  is  used  in  brine  for  pre- 
serving the  natural  color  of  salted  meats. 

Owing  to  the  great  quantity  of  oxygen  which  saltpeter  contains,  and  the 
facility  with  which  it  parts  with  it,  it  is  extensively  used  as  an  oxydizing 
agent.  When  thrown  upon  burning  coals  it  deflagrates  brilliantly.  If  paper 
be  dipped  in  a  solution  of  niter,  and  dried,  it  forms  what  is  well  known  as 
"  touch-paper,"  which,  when  once  kindled,  steadily  smoulders  away  till  con- 
sumed, and  is  hence  largely  employed  in  firing  trains  of  powder,  fireworks, 
etc. 

The  occurrence  of  fearful  explosions,  when  warehouses  containing  saltpeter 
in  large  quantities  have  been  consumed  by  fire,  has  occasioned  much  specu- 
lation as  to  whether  ignited  saltpeter  will,  under  any  circumstances,  explode. 
The  facts  in  regard  to  this  subject  are  as  follows ; — saltpeter,  when  burned  by 
itself,  will  not  explode ;  but  the  oxygen,  which  is  liberated  during  its  ignition, 
by  mingling  with  the  carbonaceous  gases  evolved  during  the  combustion, 
at  the  same  time,  of  other  substances,  may  produce  explosive  compounds. 

*  The  name  antiseptic  is  given  to  those  substances  which  resist  and  retard  the  decom- 
position of  organic  substances,  such  as  saline  bodies,  acids,  etc. 

QUESTIONS. — What  is  saleratus  ?  From  whence  is  saltpeter  mainly  obtained  ?  What 
is  supposed  to  be  its  origin  ?  How  may  saltpeter  be  formed  artificially  ?  What  are  the 
properties  of  saltpeter  ?  What  is  "  touch-paper  ?"  Will  saltpeter  explode  ? 


332  INORGANIC     CHEMISTRY. 

505.  Gunpowder , — The  principal  use  of  saltpeter  is  for  the  manufac- 
ture of  gunpowder,  which  consists  of  a  mechanical  mixture  of  niter,  sulphur, 
and  charcoal,  in  proportions  which  very  nearly  correspond  to  1  equivalent  of 
niter,  3  of  carbon,  and  1  of  sulphur ;  thus : — 

In  100  parts. 

Niter,        1  eq.  101  74'8 

Sulphur,    1  eq.    1G  13'3    - 

Charcoal,  3  eq.    18  11-9 

135  100-0 

The  great  explosive  power  of  gunpowder  Is  due  to  the  sudden  conversion 
of  the  solid  grains  into  gases  (principally  nitrogen  and  carbonic  acid) ;  these, 
at  the  ordinary  temperature  of  the  air,  would  occupy  a  space  equal  to  about 
300  times  the  bulk  of  the  powder  used ;  but  from  the  intense  heat  developed 
at  the  moment  of  the  explosion,  the  expansion  amounts  to  at  least  1,500 
times  the  volume  of  the  powder.* 

506.  Manufacture  of  Gunpowder,  —  In  the  manufacture  of 
gunpowder,  the  three  materials,  in  the  state  of  the  greatest  purity,  are  first 
pulverized  separately,  and  then  mixed  in  the  proper  proportions.  They  are 
then  slightly  moistened,  and  further  ground  and  blended  together,  in  charges 
of  42  Ibs.  each,  by  means  of  large  cylinders  or  wheels  of  iron,  weighing  sev- 
eral tons  each,  which  roll  round  over  the  powder  in  a  large  wooden  tub.  The 
mixture  is  then  spread  in  layers  of  about  an  inch  in  thickness,  between  cop- 
per plates,  and  subjected  to  an  immense  hydraulic  pressure.  A  thin,  hard 
cake  is  thus  obtained,  which  is  broken  into  small  fragments,  or  granulated,  by 
subjecting  it  to  the  action  of  toothed,  brass  rollers,  of  different  successive 
guages.  The  grains  are  next  sorted  by  means  of  sieves  of  different  sizes ; 
after  which  they  are  thoroughly  dried  by  steam-heat,  and  finally  polished  and 
glazed  by  rotating  them  in  wooden  revolving  cylinders,  with  a  small  quan- 
tity of  "  black  lead." 

The  object  of  granulating  the  powder  is  to  favor  the  rapidity  of  the  ex- 
plosion, by  leaving  interstices  through  which  the  flame  is  enabled  to  pene- 
trate, and  kindle  every  grain  at  the  same  moment.  Powder,  in  the  form  of 
fine  dust,  burns  rapidly,  but  does  not  explode.  The  firing  of  gunpowder  is 
not  absolutely  instantaneous,  inasmuch  as  gun-cotton  and  fulminating  mer- 
cury explode  much  more  rapidly — which  facts  prove  duration  in  the  explosion 


*  The  expansive  force  of  gunpowder  depends  almost  entirely  upon  the  circumstances 
tinder  which  it  is  fired.  Count  Kumford  showed,  during  the  last  century,  that  if  powder 
be  placed  in  a  closed  cavity,  and  the  cavity  be  two  thirds  filled,  the  force  will  exceed 
150,000  Ibs.  upon  the  square  inch;  and  he  estimated  that  if  the  cavity  were  entirely  filled, 
and  restrained  to  its  original  dimensions,  the  force  would  rise  to  150,000  Ibs.  per  square 
inch.  Recent  experiments,  by  Mr.  Treadwell  of  Boston,  also  tend  to  confirm  these  con- 
clusions. On  the  other  hand,  if  powder  be  fired  in  constantly-maintained  vacuum,  it 
would  not  rend  walla  made  of  cartridge-paper,  if  a  single  end  were  left  open  to  ita  escape. 

QUESTIONS. — What  is  gunpowder  ?  To  what  is  the  explosive  force  of  gunpowder  due  ? 
How  does  its  force  vary  ?  How  is  gunpowder  manufactured  ?  Why  is  powder  made  in 
grains  ?  Is  the  explosion  of  gunpowder  instantaneous  ? 


SODIUM.  333 

of  powder.*  Substances  which  explode  more  rapidly  than  gunpowder  are 
not  adapted  for  the  movement  of  projectiles,  inasmuch  as  sufficient  time  is  not 
given  to  allow  the  charge  to  receive  the  full  advantage  of  the  expansive  force 
of  the  gases  generated ;  their  action,  therefore,  is  not  to  project  the  ball,  but 
to  burst  the  gun. 

The  goodness  of  gunpowder  may  be  tested  by  placing  two  small  heaps  upon 
clean  writing-paper,  three  or  four  inches  asunder,  and  firing  one  of  them  with 
a  red-hot  wire ;  if  the  flame  ascends  quickly,  with  a  good  report,  leaving  the 
paper  free  from  white  specks,  and  not  burnt  into  holes ;  and  if  no  sparks  fly 
off  to  ignite  the  contiguous  heap,  the  powder  is  very  good  j  but  if  these  tests 
fail,  tho  ingredients  are  badly  mixed  or  impure. 

SECTION    II. 

SODIUM. 

Equivalent,  23.     Symbol,  Na  (Natrium).     Specific  gravity,  0*972. 

507.  History  and  Distribution, — This  metal  was  first 
obtained  by  Davy,  immediately  after  the  discovery  of 
potassium,  by  the  voltaic  decomposition  of  soda.  It  is 
now  prepared  very  cheaply  from  the  carbonate  of  soda,  by 
a  process  analagous  to  that  followed  in  the  preparation  of 
potassium. 

Sodium,  in  combination,  occurs  most  abundantly  in  the  mineral  kingdom, 
though  it  is  not  so  widely  diffused  as  potassium.  Its  great  storehouse  is 
common  salt,  from  which  substance  most  of  the  soda  of  commerce  is  obtained. 
"  As  potassium  is  in  some  degree  characteristic  of  the  vegetable  kingdom,  so 

*  While  the  logical  Solution  of  this  question  adds  but  little  to  our  knowledge,  we  are 
Bble  to  infer,  from  certain  experimental  results,  the  course  of  action  which  accompanies 
or  causes  the  amazingly  rapid  explosion  of  a  quantity  of  powder  confined  in  a  close  cavity. 
"  Thus,  when  the  fire  reaches  the  charge  from  the  touch-hole,  the  nearest  grains  become 
kindled,  the  hot  fluid  evolved  is  thrown  further  into  the  charge,  and  the  burning  succeeds 
successively  until  the  pressure  becomes  so  great  as  to  condense  the  air  contained  between 
the  grains  sufficiently  to  produce  the  heat  required  for  firing  these  grains,  which  are 
then  consumed  more  or  less  rapidly  as  they  are  fine  or  coarse.  We  have  then,  first, 
the  burning,  in  succession,  of  a  small  part  of  the  charge  ;  then  the  immensely  rapid, 
though  not  instantaneous,  kindling  of  every  grain  composing  it ;  and  then  the  consump- 
tion of  these  grains,  which  is  not  accomplished  without  time.  It  is  a  task  for  the  concep- 
tion to  grasp  these  events,  following  one  another  in  distinct  succession ;  each  having  its 
beginning,  middle,  and  end,  and  all  being  compressed  in  a  period  not  exceeding  l-200th 
of  a  second.  When  we  have  mastered  the  imagination  of  these  we  may  go  further,  and 
combine  with  them  the  connected  and  contemporaneous  action  of  the  ball,  which  passes 
from  rest  to  motion,  and  through  every  gradation  of  velocity  up  to  1,600  feet  per  second, 
and  leaves  the  gun  as  our  historical  period  of  1 -200th  of  a  second  expires." — TBEADWELL, 

QUESTIONS. — Why  are  compounds  more  explosive  than  gunpowder  not  adapted  for 
moving  projectiles  ?  How  is  the  goodness  of  powder  tested  ?  What  is  said  of  sodium  ? 
What  of  its  occurrence  in  nature  ? 


334  INORGANIC    CHEMISTRY. 

sodium  is  the  alkaline  metal  of  the  animal  kingdom,  its  salts  being  found  in 
all  animal  fluids." 

508.  Properties , — Sodium  is  a  white  metal,  having  the  aspect  of 
silver.     It  resembles  potassium  in  its  properties,  but  does  not  oxydate  so 
readily  as  potassium,  and  when  thrown  upon  water,  does  not  inflame,  unless 
the  water  has  been  previously  heated.    Sodium  and  all  its  salts,  when  ignited, 
communicate  to  flame  a  rich  yellow  color ;  this  reaction  may  be  illustrated 
by  holding  a  piece  of  soda- glass,  or  any  mineral  containing  soda,  in  the  flame 
of  a  blow-pipe. 

509.  The  compounds  of  sodium  have  mainly  the  same  composition  and 
properties  as  those  of  potassium. 

510.  Caustic   Soda,  or  the  Hydrate  of  Soda,  NaO,  HO,  is  prepared 
by  decomposing  carbonate  of  soda  with  quick-lime,  in  the  same  manner  as 
has  been  already  described  for  caustic  potash.     Its  properties  and  appearance 
are  also  exactly  similar  to  those  of  caustic  potash. 

511.  Chloride  of  Sodium,  JVaC  1, —  Common  Salt. — This  important 
and  well-known  compound  is  formed  when  sodium  is  burned  hi  chlorine  gas, 
and  also  when  soda  or  its  carbonate  is  neutralized  by  hydrochloric  acid. 

The  union  of  these  two  elements  is  attended  with  a  most  remarkable  con- 
densation of  volume.  Thus  24  parts  by  measure  of  common  salt  contains  no 
less  than  2 5 -8  parts  by  measure  of  sodium  (more  than  its  own  bulk),  and  no 
less  than  30  parts  by  measure  of  liquid  chlorine ;  or  in  other  words,  55*8 
parts  by  bulk  are  compressed  by  the  action  of  the  force  of  chemical  affinity 
into  24.  "  N"o  known  mechanical  force,"  says  Faraday,  "  could  have  accom- 
plished this  result;*  and  it  is  also  strange  that  such  an  amount  of  condensa- 
tion— of  squeezing  together  of  atoms — should  be  co-existent  with  such  perfect 
transparency,  for  common  salt  is  even  more  transparent  than  glass,  allowing 
a  certain  kind  of  radiant  matter  to  pass  which  stands  on  the  confines  of  light 
and  heat."  (§  206.) 

512.  Common  salt  is  found  pure  or  native  in  the  earth  in  rock-masses 
(rock-salt),   in  various  countries,   and  is  regularly  mined  or  quarried.     The 
celebrated  mine  near  Cracow,  in  Poland,  is  located  in  a  bed  of  rock-salt 
which  is  estimated  to  be  500  miles  in  length,  20  broad,  and  not  less  than 
1200  feet  thick. 

Salt  also  exists  in  solution  in  all  sea- water,  in  a  proportion  of  about  2-1?  per 
cent.,  which  amounts  to  nearly  4  oz.  per  gallon,  or  to  a  bushel  in  from  300 
to  350  gallons.  Salt  manufactured  from  sea-water  by  solar  evaporation,  ia 
termed  "  bay,"  or  "  solar  salt."  The  evaporation  is  not  carried  to  dryness, 
but  when  the  greater  part  of  the  chloride  of  sodium  is  deposited  in  crystals, 

*  The  student,  in  this  connection,  will  do  well  to  bear  in  mind,  that  physicists  are  not 
yet  fully  agreed  as  to  whether  a  liquid  is  capable  of  any  reduction  of  volume  by  any  ap- 
plication of  mechanical  pressure. 

QUESTIONS.— What  are  its  properties?  What  is  caustic  soda?  What  is  common  salt? 
How  may  it  be  formed  artificially  ?  What  singular  circumstance  attends  the  union  of  its 
elements  ?  What  is  rock  salt  ?  What  proportion  of  salt  exists  in  sea-water  ?  How  is 
salt  manufactured  from  this  source  ? 


SODIUM. 


335 


FIG.  ITS. 


the  mother-liquor  is  drawn  off.  This,  which  from  its  bitter  taste  is  tech- 
nically termed  the  "  bittern,"  retains  most  of  the  other  salts  contained  in 
sea-water,  i.  e.,  the  compounds  of  magnesia,  lime,  bromine,  etc. 

Salt  is  also  manufactured  in  large  quantities,  especially  in  the  United 
States,  by  evaporating  the  water  of  saline  springs.  From  this  source  6,000,000 
bushels  were  manufactured  in  the  State  of  New  York  (principally  in  Onon- 
daga  County)  and  3,500,000  bushels  in  the  State  of  Virginia,  during  the  year 
1856.  The  water  of  the  Onondaga  salt-springs  contain  about  one  seventh  part 
of  dry  salt.  The  estimated  amount  of  salt  manufactured  from  all  sources  in  the 
United  States  during  the  year  1856,  was  upward  of  twelve  millions  of  bushels. 

The  appearance  of  salt  varies,  according  to  the  rate  at  which  evaporation 
is  conducted.  When  boiled  down  rapidly,  it  forms  the  fine-grained  salt  used 
upon  our  tables ;  if  evaporated  more  slowly,  the  hard,  crystallized  salt,  pre- 
ferred for  the  packing  of  fish  and  meats,  is  obtained. 

Common  salt  crystallizes  in  cubes,  which  are  anhydrous,  but  crackle  or  de- 
crepitate, when  heated,  from  the  water  mechanically  confined  between  their 
plates.  If  the  evaporation  of  the  solution  of  salt  takes  place  slowly,  the 
cubical  crystals  are  large ;  but  if  it  be  rapid,  they  are  small,  and  curiously- 
arranged  in  what  is  called  a  "  hopper-shaped"  form.  Thus,  let  us  suppose  a 
small  cubical  crystal  has  formed  on  the  surface  of  the  solution.  From  its 
greater  density,  the  crystal  has  a  ten- 
dency to  fall  to  the  bottom  of  the 
liquid,  but  capillary  attraction  keeps 
it  upon  the  surface.  (See  Fig.  178.) 
New  crystals  soon  form,  which  are 
joined  to  the  first  at  the  four  upper 
edges,  and  constitute  a  frame  above 
the  first  little  cube.  (See  Fig.  179.) 
As  the  whole  descends  into  the  fluid, 
new  crystals  are  grouped  around  the 
first  frame,  constituting  a  second. 
(Fig.  180.)  Another  set,  added  in 
the  same  way,  gives  the  appearance 
shown  in  Fig.  181.  The  conse- 
quence of  this  successive  arrange- 
ment is,  that  the  crystals  are  group- 
ed into  hollow,  four-sided  pyramids, 
the  walls  of  which  have  the  appear- 
ance of  steps,  because  the  rows  of 
small  cubic  crystals  retreat  from  each 
other.  (See  Fig.  182.) 

Common  salt  is  equally  soluble  in  hot  and  cold  water ;  100  parts  of  water 
dissolve  37  parts  of  it;  so  that  a  saturated  solution,  or  the  strongest  possible 

QUESTIONS. — From  what  sources  is  salt  principally  manufactured  in  the  United  States? 
What  occasions  the  variations  in  the  appearance  of  salt  ?  What  is  said  of  the  crystalliz- 
ation of  salt  ?  What  of  its  solubility  ? 


FIG.  1T9. 


336  INORGANIC    CHEMISTRY. 

brine,  contains  3*7  per  cent  It  is  an  essential  constituent  of  the  food  of  both 
man  and  animals,  who  languish  if  it  be  supplied  in  insufficient  quantities.* 

513.  Sulphate  of  Soda,  JVaUjSOa  +  lOHO .—This  compound 
is  popularly  known  as  "  Glauber  salts,"  from  its  discoverer,  Glauber.  It  has  a 
saline,  bitter  taste,  and  is  occasionally  used  in  medicine  as  a  purgative.  It  is 
found  naturally  as  a  mineral,  and  occurs  also  in  sea- water,  and  in  many  min- 
eral springs ;  it  is  generally  prepared,  however,  by  decomposing  common  salt 
with  sulphuric  acid,  as  in  the  process  for  preparing  hydrochloric  acid. 

Glauber  salts  possess  the  peculiar  property  of  being  more  readily  soluble 
in  water  at  90°  F.  than  in  water  at  a  higher,  or  at  a  boiling  temperature.  It 
crystallizes  readily  from  a  saturated  solution  in  long  four-sided  prisms,  which 
contain  more  than  half  their  weight  of  water ;  exposed  to  air,  this  water  gra- 
dually evaporates,  and  the  crystals  crumble  to  a  fine  powder — effloresce.  A 
very  interesting  experiment  may  be  performed  by  closing  hermetically  a  flask 
containing  a  boiling  saturated  solution  of  this  salt ;  in  this  condition,  the  so- 
lution may  be  kept  for  months  without  crystallizing,  but  the  moment  air  is 
admitted,  the  whole  becomes  a  semi- solid  mass  of  crystals. 

514.  Carbonate  of  Soda,  NaO,C02  +  10IIO,—  Sal-Soda, 
Soda-Ash. — The  preparation  of  this  salt  constitutes  one 
of  the  most  important  branches  of  chemical  manufacture  ; 
immense  quantities  of  it  being  consumed  in  the  produc- 
tion of  glass,  in  the  fabrication  of  soap,  in  the  operations 
of  bleaching,  and  in  the  preparation  of  the  salts  of  soda. 

The  material  from  which  carbonate  of  soda  is  now  manufactured,  is  com- 
mon salt,  and  the  details  of  the  process  are  essentially  as  follows :  a  charge 
of  600  Ibs.  of  salt  is  placed  upon  the  hearth  of  a  well-heated  reverberatory 
furnace,  f  and  an  equal  weight  of  strong  sulphuric  acid  is  poured  upon  it 


*  "  Salt,"  says  Mungo  Park,  "is  one  of  the  greatest  of  all  luxuries  in  Central  Africa 
and  the  continued  use  of  vegetable  food  creates  so  painful  a  longing  for  it,  that  no  words 
can  describe  the  sensation."  From  time  immemorial,  it  has  been  known  that  without 
salt  man  would  miserably  perish,  and  among  horrible  punishments,  entailing  certain 
death,  that  of  feeding  culprits  on  saltless  food  is  said  to  have  prevailed  in  barbarous 
times.  The  explanation  of  this  is,  that  the  blood  contains  a  very  large  percentage  of 
common  salt ;  and  as  this  is  partly  discharged  every  day  through  the  skin  and  kidneys, 
the  necessity  of  continued  supplies  of  it  to  the  healthy  body  becomes  apparent.  The  bil6 
also  contains  soda  as  a  special  and  indispensable  constituent,  and  so  do  all  the  cartilages 
of  the  body.  Stint  the  supply  of  salt,  therefore,  and  neither  will  the  bile  be  able  properly 
to  assist  the  digestion,  or  the  cartilages  to  promptly  repair  their  waste. — JOHNSON. 

t  A  reverberatory  furnace  (Fig.  183),  used  extensively  in  the  manufacture  of  soda-ash, 
the  puddling  and  refining  of  iron,  and  in  the  smelting  of  metals,  is  a  furnace  so  arranged 
that  the  heating  is  effected,  not  by  the  fuel  itself,  but  by  tho  flame  passing  from  the  fire- 
place, /,  under  the  influence  of  a  powerful  draft,  over  a  bridge  into  a  chamber,  where  the 

QUESTIONS. — What  of  its  necessity  to  man  and  animals*  What  are  Glauber  salts? 
What  is  said  of  them  ?  What  of  their  solubility  ?  What  of  their  crystallization  ?  What 
is  soda-ash  ?  What  is  said  of  carbonate  of  soda  ?  From  what  is  it  manufactured  ?  De- 
scribe the  process.  What  is  a  reverberatory  furnace  ? 


SODIUM. 


33T 


through  an  opening  in  the  roof  of  the  furnace.  Hydrochloric  acid  is  disen- 
gaged, which  is  usually  allowed  to  escape  up  the  chimney  (§  360),  and  the 
salt  is  converted  into  sulphate  of  soda.  This  operation  is  completed  in  about 
four  hours,  and  requires  much  care  and  skill. 

The  sulphate  thus  formed  is  next  reduced  to  powder,  and  mixed  with  an 
equal  weight  of  chalk  or  limestone  (carbonate  of  lime),  and  half  as  much  fine 
coal.  The  mixture  is  then  heated  to  fusion,  with  constant  stirring,  about  200 
Ibs.  being  operated  on  at  once.  By  this  treatment  double  decomposition  is 
effected,  the  sulphate  of  soda  being  converted  into  carbonate  of  soda,  and 
the  carbonate  of  lime  into  sulphuret  of  calcium.  The  mass,  when  cold,  is 
treated  with  water,  the  carbonate  of  soda  dissolved  out,  and  the  solution 
subsequently  evaporated  to  dryness.  The  product  constitutes  the  soda-ash 
or  British  alkali  of  commerce  (anhydrous  carbonate  of  soda),  and  when  of 
good  quality  contains  from  48  to  52  per  cent,  of  pure  soda.* 


FIG.  183. 


material  to  be  acted  upon  is  placed.  The  roof  of  this  chamber 
being  concave,  reverberates  or  throws  back  the  flame  striking 
upon  it  to  the  floor  beneath — hence  the  name,  reverberatory  fur- 
nace. The  chamber  has  an  opening  upon  the  side,  A,  for  the  in- 
troduction of  materials,  and  another  opening  at  the  end  most  dis- 
tant from  the  fire.  The  chimney  is  also  provided  with  a  damper. 
D,  by  which  the  draft  is  regulated. 

*  The  discovery  and  application  of  this  method  was  one  of 
those  great  events  in  the  history  of  civilization  which  created  or 
revolutionized  whole  branches  of  industrial  art,  and  by  cheapen- 
ing the  production  of 
great  classes  of  art- 
icles of  convenience 
and  necessity,  ma- 
terially improved  the 
condition  of  the  hu- 
man race.  The  pro- 
cess in  question  was 
devised  by  Leblanc, 
a  French  chemist,  to- 
ward the  close  of  the 
last  century.  It  re- 
mained for  a  long 

time  unnoticed,  and  it  was  not  until  1820  that  any  successful  trial  was  made  with  it  in 
England.  Previous  to  this,  all  the  soda  of  commerce  was  obtained  from  the  ashes  of  sea- 
weeds, which  were  sold  in  the  market  under  the  names  of  Spanish  barilla  and  kelp ;  the 
former  being  produced  on  the  coasts  of  France  and  Spain,  and  the  latter  chiefly  on  the 
coast  of  Scotland.  Only  a  small  quantity  of  the  weight  of  these  substances,  however,  was 
an  alkali.  The  barilla  contained  about  18  per  cent.,  and  was  sold  for  about  $50  per  ton  ; 
and  the  kelp  only  5  or  6  per  cent.,  and  was  worth  $20  per  ton.  It  is  obvious,  therefore, 
that  the  soap  and  glass-maker,  in  buying  these  substances,  would,  in  the  one  case,  pur- 
chase 95  parts  of  worthless  material,  and  in  the  other  82  parts  ;  we  say  worthless,  because 
of  no  service  in  the  fabrication  of  soap  or  glass.  It  would  seem,  therefore,  that  the  intro- 
duction of  a  strong  and  cheap  alkali,  would  have  been  hailed  by  the  manufacturers  as  one 
of  the  greatest  advantages ;  but  the  fact  was  quite  the  contrary,  and  the  chemists  and 
manufacturers  found  it  extremely  difficult  to  dissipate  the  prejudice  in  favor  of  kelp  and 

QUESTION.— What  is  said  of  the  history  and  introduction  of  carbonate  of  soda  ? 

15 


838  INORGANIC    CHEMISTRY. 

515.  Bi-Carbonate    of  Soda,  N  a  0 ,  HO,  2C02,   is  obtained  by 
passing  carbonic  acid  gas  into  a  solution  of  carbonate  of  soda,  or  by  exposing 
soda-ash  to  the  carbonic  acid  generated  from  fermenting  gram,  as  in  distiller- 
ies, etc.     This  salt  is  often  sold  under  the  name  of  "  soda  saleratus." 

516.  Alkalimetry  . — As  the  purity  and  value  of  the  commercial  car- 
bonates of  potash  and  soda  differ  greatly,  it  becomes  important  to  the  buyer 

and  the  manufacturer  to  be  able  to  determine  rapidly  and  accu- 
rately the  quantity  of  available  alkali  in  a  given  sample.  This 
operation,  termed  alkalimetry,  consists  in  ascertaining  how  much 
dilute  sulphuric  acid  of  a  standard  strength  is  required  to  neutralize 
exactly  a  known  weight  of  a  particular  specimen.  A  good  article 
will  require  more  acid  than  a  poor  one ;  consequently,  the  amount 
IJ-IOJ  of  alkali  present  may  be  estimated  from  the  quantity  of  acid  con- 
sumed. In  practical  operations,  an  instrument  called  an  alkali- 
meter  is  employed.  This  consists  of  a  graduated  glass  cylinder,  or 
tube,  divided  into  degrees  (graduated) — Fig.  184) — in  which  the 
acid  used  is  measured  instead  of  being  weighed.  For  this  purpose 
a  test  acid  must  be  prepared,  of  such  a  strength  that  one  degree 
of  it  will  exactly  neutralize  one  grain  of  pure  alkali  (potash,  or 
soda).  The  number  of  degrees  then  consumed  in  neutralizing  the 
alkaline  properties  of  a  known  weight  of  a  sample,  in  solution,  will 
indicate  at  once,  in  per  cents.,  the  quantity  of  pure  alkali  in  the  ar- 
ticle tested. 

517.  Nitrate  of  Soda,  Soda- Saltpeter,  Cubic  Niter,  NaO, 
NOs,  is  a  native  product,  occurring  in  great  quantities  in  Peru  and 
Chili,  S.  A.  It  resembles  nitrate  of  potash  in  its  properties,  but 
can  not  be  used  in  the  manufacture  of  gunpowder,  as  it  freely  ab- 
sorbs moisture  from  the  atmosphere.  It  is  used,  however,  exten- 

tensively  in  the  manufacture  of  nitric  acid,  and  to  some  extent  in  agriculture, 

as  a  fertilizer. 


and  barilla.  When,  however,  the  soda-ash  was  once  introduced,  it  so  reduced  the  ex- 
pense of  making  soap,  that  the  operation  of  alkalizing  the  fats,  which  had  before  cost  $40 
per  ton,  was  effected,  in  one  third  the  time,  for  $10  per  ton.  Similar  results  followed  its 
application  to  the  manufacture  of  glass ;  and  the  business  of  manufacturing  soda-ash  in- 
creased so  fast,  that  in  1S3T,  seventeen  years  after  the  establishment  of  the  first  manufac- 
tory in  England,  the  quantity  produced  was  72,000  tons,  and  at  the  present  time  it  is 
upwards  of  200,000.  The  saving  to  the  English  nation  in  the  manufacture  of  soap  alone, 
from  the  introduction  of  Lcblanc's  process,  taking  as  a  basis  the  former  price  of  barilla, 
and  the  present  consumption  and  price  of  soda-ash  (1  ton  of  the  latter  being  equivalent  to 
8  tons  of  kelp  and  3  of  barilla),  was  estimated  in  184T  as  equal  to  twenty  millions  of  dol- 
lars per  annum ;  while  the  benefit  to  the  world  at  large  has  been,  that  the  prices  of  soap 
and  glass  have  been  reduced  so  low,  that  the  poorest  are  not  debarred  from  their  unre- 
stricted use. 

QUESTIONS.— What  is  said  of  bi-carbonate  of  soda?    What  it  alkalimetry?    What  of 
nitrate  of  soda  7 


LITHIUM. — AMMONIUM.  339 

SECTION    III. 

LITHIUM. 

Equivalent,  6.     Symbol,  L. 

518.  This  rare  metal  forms  the  basis  of  the  third  alkali, 
lithia,  and  resembles  sodium  in  appearance  and  properties. 
The  alkali,  lithia  (oxyd  of  lithium),  occurs  in  small  quan- 
tities in  a  few  varieties  of  minerals,  and  is  rarely  met  with. 

SECTION    IV. 

AMMONIUM  (HYPOTHETICAL). 

Equivalent,  18.     Symbol,  NIT* 

519.  The  alkali  ammonia  so  closely  resembles  potassa 
and  soda  in  its  properties  and  in  its  salts,  that  chemists  at 
the  present  time  generally  regard  it  as  the  oxyd  of  a  com- 
pound metal,  as  the  other  alkalies  are  oxyds  of  simple 
metals.     The  name  applied  to  this  hypothetical  metal  is 
Ammonium,  its  composition  being  1  atom  of  nitrogen,  and 
4  atoms  of  hydrogen. 

All  attempts  to  isolate  this  substance  have  failed,  from  its  tendency  to  sep- 
arate into  ammonia  and  hydrogen  gas.  It  can  be  apparently  obtained,  how- 
ever, in  combination  with  mercury.  This  fact  may  be  easily  illustrated  by 
the  following  experiment : — A  little  mercury  is  put  into  a  test-tube,  with  a 
grain  or  two  of  potassium  or  sodium  ;*  on  the  application  of  moderate  heat, 
over  a  spirit-lamp,  combination  ensues,  with  an  evolution  of  heat  and  light. 
When  cold,  the  fluid  amalgam  is  put  into  a  little  porcelain  cup,  and  covered 
with  a  strong  solution  of  sal-ammoniac  (chloride  of  ammonium).  A  double 
decomposition  immediately  ensues :  the  chlorine  and  sodium  unite  to  form  com- 
mon salt,  while  the  mercury  at  the  same  time  commences  to  increase  in  bulk, 
and  ultimately  swells  up  until  it  acquires  eight  or  ten  times  its  original  vo- 
lume, assuming  a  pasty  consistence,  without  losing  its  metallic  luster.  The 
new  substance,  exposed  to  a  temperature  of  0°  F.,  crystallizes  in  cubes,  but 
if  left  to  itself,  is  quickly  decomposed,  at  ordinary  temperatures,  into  fluid  mer- 
cury, ammonia,  and  hydrogen.  Now  it  is  evident  that  the  mercury  has  com- 
bined with  something ;  but  in  no  case  where  mercury  or  any  other  metal 


*  The  proportions  should  be  about  100  of  mercury  to  1  of  potassium  or  sodium,  by 
weight. 

QXTBSTIONS.— What  is  said  of  lithium  ?    What  of  ammonium  ?    How  may  the  apparent 
production  of  this  substance  be  illustrated  ? 


340  INOKGANIC     CHEMISTRY. 

combines  with  a  non-metallic  substance,  is  there  ever  a  retention  of  metallic 
properties  after  combination,  as  in  this  instance ;  therefore,  the  inference  is, 
that  the  substance  which  has  entered  into  combination  with  the  mercury  is  a 
metal — ammonium. 

The  fact  that  a  compound  body — cyanogen — is  generated  from  carbon  and 
nitrogen,  which  comports  itself  in  every  respect  like  the  non-metallic  element 
chlorine,  removes  every  difficulty  in  the  way  of  our  conceiving  that  a  com- 
pound may  also  be  formed  from  nitrogen  and  hydrogen,  which  may  have  the 
properties  of  a  metal 

According  to  the  ammonium  theory,  all  the  salts  of  ammonia  are  derived 
from  this  radical,  and  correspond  in  constitution  to  the  salts  of  the  simple 
metals. 

520.  Chloride   of   Ammonium,   Nfl4   Cl.—  Sal- Ammoniac.—  This 
substance,  which  is  a  compound  of  ammonium  and  chlorine,  is  the  most  im- 
portant of  all  the  salts  of  ammonium,  and  occurs  naturally  as  a  volcanic  pro- 
duct.    It  was  formerly  imported  from  Egypt,  as  a  product  of  distillation  from 
dried  camel's  dung,  and  from  its  having  been  originally  procured  from  a  dis- 
trict in  Northern  Africa,  near  the  temple  of  Jupiter  Ammon,  the  name  am- 
monia originated.     It  is  now,  however,  manufactured  in  large  quantities,  from 
the  ammoniacal  liquors  formed  in  the  manufacture  of  coal-gas,  and  from  the 
condensed  products  of  the  distillation  of  bones  and  other  animal  refuse,  in  the 
preparation  of  animal  charcoal.    These  are  first  treated  with  hydrochloric  acid, 
and  the  resulting  liquors  evaporated  to  dryness.    The  residue  is  then  subjected 
to  heat  in  iron  vessels,  when  the  chloride  of  ammonium  volatilizes  in  dense 
white  fumes,  which  condense,  on  cooling,  into  white,  semi-transparent,  fibrous 
masses,  the  sal-ammoniac  of  commerce. 

Sal-ammoniac  has  a  sharp,  acrid  taste,  corrodes  metals  powerfully,  and  is 
readily  soluble  in  water.  It  does  not,  however,  possess  the  characteristic  odor 
of  ammonia.  It  constitutes  the  source  from  whence  most  of  the  salts  of  am- 
monia are  prepared. 

521.  Ammonia,   N  H40  —  Volatile  Alkali,  Hartshorn.— This  alkali  exista 
in  the  atmosphere,  in  the  juices  of  certain  plants,  in  clayey  and  peaty  soils, 
and  is  freely  evolved,  in  combination,  from  the  craters  of  volcanoes. 

522.  Preparation . — Ammonia  can  not,  under  ordinary  circumstances, 
be  formed  by  the  direct  union  of  its  elements.     A  series  of  electric  sparks, 
however,  passed  through  a  mixture  of  hydrogen  and  nitrogen,  will,  after  a 
time,  generate  a  limited  quantity  of  it.     The  production  of  ammonia,  on  the 
contrary,  by  the  indirect  combination  of  hydrogen  and  nitrogen,  is  a  circum- 
stance of  continual  occurrence.     It  especially  takes  place  during  the  spon- 
taneous decomposition  of  animal  and  vegetable  substances  which  contain 
hydrogen  and  nitrogen,  and  in  almost  every  process  of  oxydation  in  the 

QTJESTIONB. — Have  we  any  reason  to  doubt  the  possibility  of  the  existence  of  a  com- 
pound metal?  What  is  sal-ammoniac?  What  is  said  of  its  natural  occurrence  ?  What 
of  its  manufacture  ?  What  is  said  of  the  natural  occurrence  of  ammonia  ?  What  of  its 
production  ? 


AMMONIUM. 


341 


FIG.  185. 


presence  of  moisture ;  in  the  latter  case,  the  hydrogen,  at  the  moment  of 
liberation  (in  a  nascent  state)  from  the  water  by  deoxydation,  enters  into 
combination  with  the  nitrogen  of  the  atmosphere. 

523.  Ammonia  is  usually  obtained  by  subjecting  a  mixture  of  quick-lime 
and  sal-ammoniac  to  a  gentle  heat  in  a  flask  or  retort ; — the  lime  decom- 
poses the  chloride  of  ammonium,  forming  chloride  of  calcium,  and  liberating 
free  ammonia,  which  latter  escapes  as  a  colorless,  transparent  gas.  The  same 
mixture  slowly  evolves  ammo- 
nia at  ordinary  temperatures, 
and  is  sometimes  used  for  the 
filling  of  smelling-bottles.  For 
experimental  purposes,  ammo- 
niacal  gas  is  best  prepared  by 
heating  a  strong  solution  of 
ammonia  in  a  glass  retort,  and 
collecting  the  evolved  gas  over 
mercury,  or  by  displacement, 
as  is  represented  in  Fig.  185. 
When  collected  by  displace- 
ment, the  gas  must  be  allowed 
to  pass  into  the  bottle  until  a 
piece  of  reddened  litmus  paper 
held  to  the  mouth  is  imme- 
diately turned  blue.  The  tube  is  then  withdrawn,  and  the  stopper,  slightly 
greased,  is  inserted. 

524.  Properties  , — Ammonia  thus  produced  is  a  gas,  which  is  easily 
condensed  to  a  liquid  by  a  reduction  of  temperature  ( — 40°  F.)  or  by  pres- 
sure. It  has  an  extremely  pungent  smell,  and  instantly  kills  an  animal  im- 
mersed in  it ;  but  when  largely  diluted  with  air,  it  is  an  agreeable  stimulant. 
From  the  fact  that  ammonia  was  formerly  prepared  by  distilling  the  horns 
of  deers  and  harts,  it  is  often  popularly  called  "  hartshorn." 

Ammonia-  does  not  support  the  flame  of  burning  bodies,  but  is  slightly 
combustible.  A  jet  of  gas  directed  across  the  stream  of  hot  air  issuing  from 
a  lighted  Argand  lamp,  burns  with  a  pale  green  flame.  It  acts  strongly  as  an 
alkali,  turning  vegetable-blues  green,  restoring  the  blue  color  of  reddened 
litmus,  and  neutralizing  the  most  powerful  acids.  The  change,  however,  of 
vegetable  colors  produced  by  ammonia,  owing  to  its  great  volatility,  is  not 
permanent ;  but  the  vegetable  substances  regain  their  colors  after  a  time  by 
exposure  to  the  air,  which  is  not  the  case  when  the  change  is  effected  by  the 
fixed  alkalies.  Ammonia  is,  therefore,  often  called  the  "  volatile  alkali." 

Any  volatile  or  gaseous  acid  brought  into  an  atmosphere  containing  am- 
monia, produces  a  white  cloud,  from  the  formation  of  a  solid  salt.  This 
property  is  often  employed  to  detect  the  presence  of  ammonia  in  quantities 

QUESTIONS. — How  is  ammonia  obtained  practically?  What  are  the  properties  of  am- 
monia  ?  Why  is  ammonia  sometimes  called  hartshorn  ?  How  may  the  presence  of  am- 
monia be  detected  ? 


342  INORGANIC     CHEMISTRY. 

too  small  to  be  recognized  by  their  odor.     The  reaction  may  be  illustrated  by 
p        Rfi  bringing  a  rod  of  glass,  or  a  strip  of  wood  moist- 

ened with  dilute  hydrochloric  acid,  near  to  a  vessel 
or  substance  evolving  ammonia ; — chloride  of  am- 
monia being  formed.  (See  Fig.  186.) 

"Water  dissolves  ammoniacal  gas  in  large  quan- 
tities, and  with  great  rapidity ; — water  at  50°  F. 
absorbing  about  670  times  its  volume.  When  a 
piece  of  ice  is  introduced  into  a  jar  of  gas  standing 

over  mercury,  it  instantly  liquefies,  and  by  condensing  the  gas  forms  a 

vacuum.     The  almost  instantaneous  absorption  of  this  gas  by  water  may  be  also 

illustrated  by  closely  fitting  a  perforated  cork  and  tube 

into  the  mouth  of  a  jar  containing  ammonia,  and  in- 

verting  the  jar  in  a  vessel  of  water.     (See  Fig.  187.) 

The  first  portion?  of  water  that  enter  the  jar  absorb 

the  gas  so  rapidly,  that  a  vacuum  is  created,  and  a 

miniature  fountain  produced. 

525.  Solution    of   Ammonia  • — The    aqueous ( 
solution  of  ammonia,  known  as  aqua  ammonia,  liquid 
ammonia,  etc.,  is  a  reagent  much  used  in  pharmacy 
and  chemistry.     It  is  a  colorless,  transparent  liquid,  and 
has  all  the  pungent  and  alkaline  properties  of  the  gas. 

"When  applied  to  the  skin  in  a  concentrated  form,  it  blisters  it,  and  is  hence 
often  termed  caustic  ammonia.  Exposed  to  the  ah*,  ammonia  escapes  from 
it,  and  heat  disengages  it  abundantly. 

526.  There  are  several  carbonates  of  ammonia.     The  ordinary  sal-volatile 
of  the  shops,  which  constitutes  the  basis  of  the  well-known  "  smelling-salts," 
is  a  sesqui  carbonate  of  ammonia,  2NH40,  3COs.     It  is  a  white  solid,  highly 
volatile,  and  when  exposed  to  the  air  absorbs  carbonic  acid,  and  becomes 
converted  into  an  inodorous  bi-carbonate.     This  salt  is  frequently  used  by 
bakers  in  the  place  of  yeast,  for  raising  bread,  cake,  etc.— heat  converting  it 
into  gas,  which,  escaping  from  the  dough,  renders  it  light  and  porous. 

/  527.  flydrosulphuret  of  Ammonia,  Sulphide  of  Am- 
monium, NH4,  S-j-HS . — This  reagent,  which  is  extensively  employed 
in  chemical  analysis,  is  formed  by  transmitting  sulphuretted  hydrogen  through 
a  solution  of  ammonia  to  saturation.  The  solution  thus  prepared  should  be 
kept  cold  and  in  closed  glass  bottles. 

528.  General  Properties  of  the  Alkalies , — The  alkalies 
are  the  strongest  bases  known  in  chemistry.  They  are  all  soluble  in  water, 
have  alkaline  properties  hi  the  most  marked  degree,  and  exert  a  caustic  and 
decomposing  action  upon  organic  substances. 

Most  of  the  salts  which  the  alkalies  form  with  acids  are  soluble  in  water. 

QUESTIONS.— What  is  said  of  the  absorption  of  ammonia  by  water  ?  How  may  this  be 
Illustrated  ?  What  is  aqua  ammonia  ?  What  are  its  properties  ?  What  is  said  of  car- 
bonate of  ammonia  ?  What  is  hydrosulphuret  of  ammonia  ?  What  are  the  general  prop- 
erties of  the  alkalies  ?  What  is  said  of  their  salts  ? 


BARIUM  —  STRONTIUM.  343 

This  is  especially  true  of  their  carbonates,  which  also  exhibit  alkaline  prop- 
erties. Carbonic  acid  can  not  be  expelled  from  the  alkaline  carbonates  by 
heating,  but  it  escapes  immediately  with  effervescence,  on  the  addition  of 
other  acids. 

"With  the  fats  and  fixed  oils,  the  alkalies  yield  soaps,  which  are  soluble  in 
water. 


CHAPTER    X, 

METALS     OF     THE     ALKALINE     EARTHS. 

529.  THE  metals  belonging  to  this  class  are  Barium, 
Strontium,  Calcium,  and  Magnesium. 

Their  oxyds,  baryta,  strontia,  lime,  and  magnesia,  are  called  alkaline 
earths,  because  they  possess  an  earthy  appearance,  together  with  some  alka- 
line properties.  *  The  metals  of  the  alkaline  earths,  like  the  metals  of  the  al- 
kalies, are  all  characterized  by  an  intense  affinity  for  oxygen,  and  their  isola- 
tion in  a  pure  state  is  a  matter  of  great  difficulty. 

SECTION    I. 

BARIUM    AND    STRONTIUM. 

530.  Barium, — Equivalent,  68'5;  Symbol,  Ba.~Barium 
is  a  white,  malleable  metal,  which  is  fusible  under  a  red 
heat.     It  was  first  discovered  by  Davy,  and  was  named 
Barium  (from  fiapv?,  heavy)  in  allusion  to  the  great  density 
of  its  compounds. 

The  essential  features  of  the  method  at  present  adopted  for  obtaining  the 
metals  of  the  alkaline  earths,  is  to  subject  their  chlorides  to  heat  in  contact  with 
potassium,  or  sodium.  These  elements,  from  their  greater  affinity  for  chlorine, 
decompose  the  earthy  chlorides,  and  leave  their  metallic  bases  in  a  state  of 
greater  or  less  purity. 

Baryta  occurs  in  nature  chiefly  as  a  sulphate — sulphate  of  baryta,  heavy 
spar — in  beautiful,  white,  tabular  crystals,  often  associated  with  copper  or 
lead  ores ;  this  mineral,  when  ground  to  powder,  is  extensively  used  for 
the  adulteration  of  white  lead.  A  native  carbonate  is,  however,  the  source 
from  whence  most  of  the  other  preparations  of  baryta  are  obtained. 

The  Chloride  of  Barium,  BaCl,  is  the  most  common  soluble  salt  of  barium ; 

QUESTIONS. — What  are  the  metals  of  the  alkaline  earths  ?  What  are  their  properties  ? 
What  their  oxyds  ?  What  is  said  of  barium  ?  By  what  process  are  the  metals  of  the 
alkaline  earths  obtained  ?  What  is  said  of  the  natural  occurrence  of  baryta  ?  What  ar« 
its  principal  salts  ? 


344  INORGANIC     CHEMISTRY. 

it  is  much  used  in  chemical  analysis  as  a  test  for  the  presence  of  sulphuric 
acid  in  solution — which  unites  with  baryta  to  form  a  white,  in  soluble  sul- 
phate. 

531.  Strontium, — Equivalent,^;  symbol,  Sr. — Stron- 
tium is  a  white  metal,  greatly  resembling  barium. 

Its  oxyd,  strontia,  occurs  in  nature  as  a  carbonate  (the  mineral,  strontianite) 
and  more  abundantly  as  a  sulphate  (celestine).  The  most  remarkable  charac- 
teristic of  the  strontia  salts,  is  that  of  communicating  a  magnificent  crimson 
tint  to  the  flame  of  burning  substances.  The  red  fires  of  the  pyrotechnists 
are  composed  of  nitrate  of  strontia,  chlorate  of  potash,  sulphur,  and  antimony. 
This  reaction  may  be  illustrated  by  inflaming  a  little  alcohol,  in.  which  chlo- 
ride of  strontium  has  been  dissolved. 

SECTION   II. 

CALCIUM. 

Equivalent,  20.     Symbol,  Ca. 

532.  Calcium  is  a  light,  yellow  metal,  of  the  color  of 
gold  alloyed  with  silver.     It  is  very  malleable,  and  can  be 
hammered  into  leaves  as  thin  as  writing-paper.     It  melts 
at  a  red  heat,  and  oxydizes  in  the  air  at  ordinary  temper- 
atures.    In  combination,  as  lime,  it  forms  one  of  the  most 
abundant  and  important  constituents  of  the  crust  of  the 
globe. 

533.  Lime,    C  a  0  • — Oxyd  of  Calcium. — Lime  is  obtained  in  a  state  of 
purity  by  heating  pure  carbonate  of  lime  (calcareous  spar)  in  an  open  crucible, 
for  some  hours,  to  full  redness :  the  carbonic  acid  is  driven  off  by  the  heat, 
and  the  lime  remains.     For  commercial  purposes,  it  is  prepared  by  heating 
common  limestone,  which  is  an  impure  carbonate  of  lime,  in  a  stone  kiln  or 
furnace,  the  interior  of  which  is  somewhat  in  the  form  of  a  hogshead,  and  is 
filled  with  alternate  layers  of  limestone  and  fuel.     The  lime,  as  it  is  burned, 
gradually  sinks  down,  and  is  removed  by  openings  at  the  base  of  the  furnace, 
•while  fresh  supplies  of  fuel  and  limestone  are  supplied  at  the  top.     In  this 
way  the  furnace  may  be  kept  in  action  for  a  great  length  of  time  without  in- 
terruption. 

534.  Properties . — Lime  as  thus  prepared  is  termed  "  quicklime,"  or 
caustic  lime,  and  in  a  state  of  purity  has  resisted  all  attempts  to  fuse  it, 
"When  water  is  poured  upon  quicklime,  it  swells  up,  and  enters  into  combina- 
tion with  the  water,  forming  hydrate  of  lime,  or  slacked  lime.     If  the  propor- 
tion of  water  is  about  half  the  weight  of  the  lime  employed,  a  light,  dry  pow- 

QUESTIONS.— What  is  said  of  strontium  ?  What  is  a  characteristic  of  its  salts?  What 
is  calcium  ?  How  is  lime  prepared  ?  What  is  quicklime  ?  What  is  slacked  lime  ? 


CALCIUM.  345 

der  is  formed,  accompanied  with  a  powerful  evolution  of  heat— sufficient  to 
occasion  the  ignition  of  wood.  The  hydrate  which  is  thus  formed  is  a  definite 
compound  of  1  equivalent  of  lime  with  1  equivalent  of  water.  Lime,  also, 
when  exposed  to  the  air,  slowly  attracts  both  water  and  carbonic  acid,  and 
crumbles  to  white  powder — "air-slacked  lime." 

Lime  is  soluble  in  about  700  parts  of  water,  forming  what  is  called  "lime- 
water."  It  is  more  soluble  in  cold  than  in  hot  water,  the  latter  dissolving 
only  half  as  much  as  the  former.  Lime-water  is  characterized  by  a  nauseous 
taste,  and  decided  alkaline  properties.  It  restores  the  blue  of  reddened  lit- 
mus, and  changes  the  blue  infusion  of  cabbage  to  green.  Exposed  to  the  air, 
it  gradually  absorbs  carbonic  acid ;  a  pellicle  of  carbonate  of  lime  forms  upon 
its  surface,  which,  if  broken,  is  succeeded  by  another  pellicle,  until  the  whole 
of  the  lime  is  separated  from  the  solution,  in  the  form  of  an  insoluble  car- 
bonate. 

Lime  diffused  through  water  forma  milk  or  cream  of  lime. 

Quicklime  exerts  a  corrosive  and  destructive  action  upon  the  skin,  nails, 
and  hair,  and  upon  some  vegetable  substances.  Advantage  is  taken  of  this 
property  to  remove  the  hair  from  hides,  preparatory  to  tanning,  by  immersing 
them  in  milk  of  lime.* 

Lime  is  also  largely  employed  as  a  manure,  and  is  particularly  valuable 
upon  very  rich  vegetable  soils,  such  as  those  formed  from  reclaimed  peat-bogs  ; 
its  effects  in  these  cases  are  due  to  the  decomposition  of  the  organic  matter, 
which  it  renders  soluble  and  capable  of  assimilation,  by  plants.  Lime  formed 
from  limestone,  which  contains  much  magnesia,  is  unsuited  for  agricultural 
purposes.  Lime  should  not  be  mixed  with  manures  in  the  state  of  decom- 
position, since  it  liberates  the  ammonia  contained  in  them,  and  impairs  their 
value  as  fertilizers. 

535.  Mortars  and  Cements  , — The  most  important  practical  appli- 
cation of  lime  is  for  the  manufacture  of  mortars  and  cements.  Pure  lime, 
when  made  into  a  paste  with  water,  forms  a  somewhat  plastic  mass,  which 
sets  into  a  solid  as  it  dries,  but  gradually  cracks  and  falls  to  pieces.  It  does 
not  possess  sufficient  cohesion  to  be  used  alone  as  mortar.  To  remedy  this 
defect,  and  to  prevent  the  shrinkage  of  the  mass,  the  addition  of  sand  is  found 
to  be  necessary. 

The  proportions  of  lime  and  sand  hi  good  mortar,  vary ;  the  amount  of 


*  According  to  Dr.  John  Davy,  of  England,  the  opinion  popularly  entertained,  that 
quicklime  exercises  a  corroding  and  destructive  influence  upon  animal  and  vegetable  mat- 
ter in  general,  and  that  animal  bodies  exposed  to  its  action  rapidly  decompose  and  decay, 
is  wholly  erroneous.  The  results  of  numerous  experiments  made  by  him,  seem  to  show, 
that  with  the  exception  of  the  cuticle,  nails,  and  hair,  lime  exerts  no  destructive  action 
on  animal  tissues,  but  that  its  influence  is  antiseptic.  In  the  case  of  vegetable  substances, 
also,  the  action  was  similar,  and  instead  of  promoting,  it  arrested  fermentation. 

QUESTION.— When  ia  lime  said  to  be  air-slacked?  What  is  said  of  the  solubility  of 
lime?  What  are  the  properties  of  lime-water?  What  is  cream  of  lime?  What  is  said 
of  the  caustic  action  of  lime  ?  What  of  its  uses  in  agriculture  ?  What  is  mortar  ?  What 
is  the  necessity  of  sand  in  mortar  ? 

15* 


346  INORGANIC    CHEMISTRY. 

sand,  however,  always  exceeding  that  of  lime,  and  generally  in  the  proportion 
of  4  to  1.  The  more  sand  that  can  be  incorporated  with  the  lime  the  better, 
provided  the  necessary  degree  of  plasticity  is  preserved.  That  sand  is  most 
suitable  for  mortar  which  is  wholly  silicious,  and  whose  particles  are  sharp,  or 
not  rounded  by  attrition. 

The  cause  of  the  hardening  of  mortar  is  not  thoroughly  understood  ;  the 
explanation  generally  given  is,  that  the  water  gradually  evaporates,  and  the 
lime,  by  a  sort  of  crystallization,  adheres  to  the  particles  of  sand,  and  unites 
them  together.  A  portion  of  the  lime,  also,  by  absorption  of  carbonic  acid 
from  the  air,  is  gradually  converted  into  carbonate  of  lime.  In  the  course  of 
tune,  also,  a  chemical  combination  takes  place  between  the  silica  of  the  sand 
and  the  lime,  forming  a  compound  of  silicate  and  hydrate  of  lime,  which  pos- 
sesses great  hardness.  This  reaction  explains  the  remarkable  hardness  often 
observed  in  the  mortar  of  old  buildings. 

It  is  an  advantage  to  moisten  bricks  and  stones  before  applying  mortar  to 
them,  in  order  that  they  may  not  absorb  water  from  the  mortar,  and  thus 
cause  it  to  set  too  rapidly.  The  completeness  of  the  hardening  of  mortar,  de- 
pends upon  a  thorough  intermixture  of  the  lime  and  the  sand. 

636.  Hydraulic  Cements , — Ordinary  mortar,  when  placed  in  water, 
gradually  softens  and  disintegrates,  while  the  lime  dissolves  away ;  it  can  not, 
therefore,  be  used  for  subaqueous  constructions.  Some  limestones,  however, 
which  contain  about  20  per  cent,  of  clay  (silicate  of  alumina),  afford  lime 
which  possesses  the  property  of  hardening  under  water.  Such  limes  are 
known  as  hydraulic  limes,  or  cements,  and  may  be  artificially  imitated  by  mix- 
ing with  ordinary  lime  a  due  proportion  of  clay  not  too  strongly  burnt.* 

Concrete  is  a  mixture  of  hydraulic  lime  with  small  pebbles,  coarsely 
broken. 

537.  Carbonate  of  Lime,  CaO,C 0<,.— - This  substance  is  one  of 
the  most  abundantly  diffused  compounds  in  nature.  In  its  amorphous  condi- 
tion it  forms  the  different  varieties  of  limestone,  chalk,  and  calcareous  marl ; 
it  is  also  the  principal  constituent  of  corals  and  shells,  and  enters,  to  some  ex- 
tent, into  the  composition  of  the  bones  of  animals. 

The  term  limestone  is  applied  to  those  stones  which  contain  at  least  half 
their  weight  of  carbonate  of  lime ;  and  according  to  the  other  prevailing  in- 
gredients, a  limestone  may  be  argillaceous  (clayey),  magnesian,  ferruginous 
(containing  iron),  bituminous,  foetid,  etc. 

*  The  rapidity  with  which  different  kinds  of  hydraulic  limes  set,  varies  -with  their  com- 
position. If  the  clay  do  not  exceed  10  per  cent,  of  the  mass,  the  mortar  requires  several 
•weeks  to  harden.  If  the  clay  amount  from  15  to  25  per  cent.,  it  sets  in  two  or  three  days ; 
and  if  from  25  to  35  per  cent,  of  clay  be  present,  it  sets  in  a  few  hours.  The  substance  to 
which  the  term  Roman  cement  is  applied,  is  a  lime  of  this  latter  composition.  In  order 
that  hydraulic  lime  should  properly  harden,  it  should  not  be  submerged  until  it  begins  to 
Bet. — MILLER, 

QUESTIONS. — What  is  the  cause  of  the  hardening  of  mortar  ?  What  advantage  is  it  to 
moisten  bricks,  etc.,  before  applying  mortar  ?  What  are  hydraulic  cements  f  What  is 
Roman  cement?  What  is  concrete?  What  is  said  of  the  distribution  of  carbonate  of 
lime  ?  What  is  a  limestone  ? 


CALCIUM.  347 

The  term  marble  is  applied  to  those  varieties  of  compact  limestone  which 
are  capable  of  being  worked  in.  all  directions,  and  also  of  taking  a  good  polish. 

Carbonate  of  lime  is  found  in  a  greater  variety  of 
crystalline  forms  than  any  other  known  substance. 
Its  primary  form  is  a  rhombohedron,  as  seen  in  double 
refracting,  or  Iceland  spar  (see  Fig.  187) ;  but  of  this 
figure  over  650  modifications  are  known  to  mineral- 
ogists. Carbonate  .of  lime  also  ctystallizes  in  another 
primary  form,  that  of  six-sided  prisms,  as  in  the  min- 
eral aragonite. 

538.  Carbonate  of  lime  dissolves  in  pure  water  to  the  extent  of  about  two 
grains  to  the  gallon,  but  in  water  charged  with  carbonic  acid  it  is  taken  up 
freely,  and  again  deposited  as  the  gas  escapes — often  in  anhydrous  crystals. 
It  is  in  this  way  that  the  enormous  rock  masses  of  crystalline  carbonate  of 
lime  are  supposed  to  have  been  formed.     This  action,  which  has  been  before 
alluded  to,  (§  434),  is  beautifully  illustrated  in  the  formation  of  stalactites 
and  stalagmites  in  caverns.      "Water  charged  with  carbonic  acid  and  car- 
bonate of  lime,  falls  in  drops  from  the  roof  of  the  cavern ;    but  each  drop 
before  falling  remains  suspended  for  a  time,  during  which  a  part  of  the  car- 
bonic acid  escapes,  and  a  minute  portion  of  carbonate  of  lime  is  left  behind. 
It  also  deposits  another  minute  portion  of  calcareous  matter  on  the  spot 
upon  which  it  falls,  and  as  the  drops  are  formed  nearly  on  the  same  spot  for 
years  together,  a  dependent  mass  like  an  icicle  is  formed  from  the  roof — the 
stalactite ;  while  another  incrustation  gradually  rises  up  from  the  floor  beneath 
it — the  stalagmite.     In  the  process  of  time  the  two  may  meet  and  form  a 
continuous  column.     (See  Fig.  188.) 

539.  Building    Materials  , — Carbonate  of  lime  is  a  material  much 
used  in  architecture  and  building,  but  all  its  varieties  are  not  equally  valuable 
for  this  purpose.     Those  varieties  of  marble  which  exhibit  large  crystals,  or 
contain  disseminated  throughout  their  mass  crystals  of  sulphuret  of  iron,  have 
comparatively  little  strength,  and  are  liable  to  disintegration.     The  stone  of 
which  the  "Washington  Monument  at  "Washington  is  constructed,  is  an  ex- 
ample.    On  the  other  hand,  very  fine-grained  porous  limestones,  and  also 
those  varieties  of  porous  sandstones  which  are  termed  free-stones,  are  ill- 
adapted  for  the  external  portions  of  buildings,  since  they  are  liable  to  split 
into  flakes  after  a  few  years'  exposure  to  the  weather.     This  generally  arises 
from  the  absorption  of  water,  and  its  expansion  by  freezing  in  the  interior 
of  the  stone  during  winter.     A  simple  and  ingenious  method  of  ascertaining 
whether  a  stone  is  liable  to  this  defect,  is  to  thoroughly  soak  a  smoothly-cut 
block,  one  or  two  inches  on  a  side,  in  a  solution  of  sulphate  of  soda.     On 
subsequently  drying  the  block  in  the  air,  the  sulphate  of  soda  crystallizes  in 

QUESTIONS.— What  is  marble  ?  What  is  said  of  crystallized  carbonate  of  lime  ?  What 
is  the  supposed  origin  of  crystallized  carbonate  of  lime  ?  What  are  stalactites  and  stalag- 
mites ?  Explain  their  formation  ?  What  is  said  of  the  adaptability  of  carbonate  of  lime 
to  building  purposes  ?  Why  are  porous  stones  liable  to  disintegrate  ?  How  may  tha 
durability  of  a  stone  be  tested  ? 


348  INORGANIC    CHEMISTRY. 

the  pores  of  the  material,  and  tends  to  split  off  fragments  from  its  surface. 
The  resistance  which  the  stone  opposes  to  this  action  affords  a  basis  for  es- 
timating its  durability.* 

FIG.  188. 


640.  Sulphate  of  Lime,  C  a  0  ,  S  03.  —  Gypsum,  —  This  salt,  as 
commonly  met  with,  is  a  hydrate — CaO,  S03+2HO — and  occurs  abundantly 
in  nature.  In  transparent  plates  it  is  termed  "  selenite,"  but  in  a  fibrous, 
granular,  compact,  or  earthy  form  it  constitutes  the  different  varieties  of  gyp- 
sum and  alabaster.  "When  ground  to  a  fine  powder,  it  is  known  in  the 
arts  as  "  Plaster  of  Paris,"  from  the  circumstance  of  the  mineral  being  ex- 
tensively found  in  the  vicinity  of  the  French  capital. 

Gypsum  is  extensively  used  in  agriculture  as  a  manure ;  but  its  most  re- 
markable property,  and  the  one  for  which  it  is  the  most  valued,  is  the  power 


*  In  selecting  a  stone  for  architectural  purposes,  we  may  be  able  to  form  a  very  good 
opinion  of  its  durability  and  permanence,  by  visiting  the  locality  from  whence  it  was  ob- 
tained, and  observing  the  condition  of  the  natural  surfaces  exposed  to  the  weather.  For 
example,  if  the  rock  be  a  granite,  and  it  be  very  uneven  and  rough,  it  may  be  inferred  that 
it  is  not  very  durable:  that  the  feldspar,  which  forms  one  of  its  component  parts,  is  more 
readily  decomposed  by  the  action  of  moisture  and  frost  than  the  quartz,  another  ingre- 
dient, and  therefore  that  it  is  very  unsuitable  for  building  purposes.  Moreover,  if  it  pos- 
sess an  iron-brown,  or  rusty  appearance,  it  may  be  regarded  as  highly  perishable,  owing 
to  the  attractiou  which  this  metal  has  for  oxygen — causing  the  rock  to  increase  in  bulk, 
and  so  disintegrate. 

The  following  is  the  comparative  strength  of  some  of  our  best-known  building  materials 
in  resisting  a  crushing  force.  The  best  varieties  of  Quincy  granite  (sienite)  will  sustain  a 
pressure  of  29,000  Ibs.  per  square  inch ;  good  compact  red  sandstone,  9,000  Ibs. :  a  variety 
of  sandstone  called  the  "  Malone,1'  from  northern  New  York,  24,000  Ibs.  ;  ordinary  mar- 
bles, from  7,000  to  10,000 :  the  poorer  varieties  of  sandstone,  like  that  composing  the 
body  of  the  capitol  at  Washington,  5,000. 

QUESTIONS. — What  is  the  constitution  of  gypsum?  Under  what  names  is  it  known? 
For  what  is  it  used  ? 


MAGNESIUM.  349 

it  possesses,  after  it  has  been  deprived  of  water  by  a  heat  not  exceeding 
300°  F.,  of  again  combining  with  water  and  forming  a  hard,  compact  mass. 
When  the  dried  powder,  known  as  "  boiled  plaster,"  is  made  into  a  thin  paste 
with  water,  the  mixture  becomes  solid  in  a  few  minutes ;  a  chemical  combi- 
nation being  formed  of  2  equivalents  of  water  and  1  of  sulplmret  of  lime, 
which  eventually  becomes  as  hard  as  the  original  gypsum.  This  power  of 
resolidifying  renders  gypsum  applicable  for  taking  copies  of  objects  of  every 
description,  and  for  the  construction  of  molds  and  models. 

If  the  powdered  g}-psum  is  subjected  to  a  heat  much  exceeding  300°  F.  it 
loses  its  property  of  solidifying  when  mixed  with  water.  By  mixing  gypsum 
with  1  or  2  per  cent,  of  alum,  sulphate  of  potash,  or  borax,  it  forms,  when 
mixed  with  water,  a  material  much  harder  than  ordinary  plaster,  and  capable 
of  taking  a  high  polish.  Artificial  colored  marbles,  ealled  "  Scagliola"  are 
formed  of  gypsum,  alum,  isinglass,  and  coloring  materials,  incorporated  into 
a  paste.  Stucco  is  a  combination  of  Plaster  of  Paris  with  a  solution  of  gela- 
tine, or  strong  glue. 

541.  Hyposulphite    of    Lime,    CaO,  S202  is  an   abundant   con- 
stituent of  the  refuse  lime  of  gas-works,  and  by  exposure  to  the  air  gradu- 
ally passes  into  sulphate  of  lime  (gypsum).      Gas-lime  has  been  used  for 
agricultural  purposes,  but  it  probably  possesses  little  or  no  value  as  a  fertil- 
izer.    It  has,  however,  been  recommended  for  mossy  land  and  for  composts. 
All  the  hyposulphites  act  as  depilatories,  or  hair -removers,  and  many  of  the 
depilatory  powders  sold  by  druggists  are  compounds  of  this  character. 

542.  Chloride    of   Calcium,    CaCl,  is  formed  by  dissolving  car- 
bonate of  lime  in  hydrochloric  acid.     The  saturated  solution  evaporated  to 
dryness,  and  the  residue  fused,  yields  a  white  crystalline  solid,  which  pos- 
sesses so  great  an  attraction  for  moisture,  that  it  is  used  for  drying  gases,  and 
for  depriving  alcohol,  ether,  and  other  liquids,  of  water,  by  distilling  them  in 
contact  with  it.    "When  mixed  with  snow  or  ice,  it  forms  a  powerful  freezing 
mixture. 

SECTION    III. 

MAGNESIUM. 

Equivalent,  12. — Symbol,  Mg. 

543.  Magnesium  is  a  malleable  metal  of  the  color  of  silver,  and  in  combin- 
ation, is  an  abundant  constituent  of  the  crust  of  the  earth.     Associated  with 
lime,  as  a  double  carbonate  of  lime  and  magnesia  (oxyd  of  magnesium),  it 
forms  magnesian  limestone,  or  dolomite.     United  with  silica,  as  a  silicate  of 
magnesia,  it  enters  more  or  less  extensively  into  the  formation  of  many  rocks, 
and  a  great  variety  of  minerals — such  as  soapstone  or  steatite,  serpentine,  talc, 


QUESTIONS. — What  are  its  properties  ?  How  may  plaster  of  Paris  be  hardened  ?  "What 
is  scagliola?  What  is  stucco  ?  What  is  said  of  hyposulphite  of  lime  ?  "What  of  the  ag- 
ricultural value  of  gas-lime?  What  peculiar  property  do  all  the  hyposulphites  possess? 
What  is  said  of  chloride  of  calcium?  What  is  said  of  magnesium  and  its  distribution? 
What  is  dolomite  ?  Of  what  minerals  is  magnesia  a  principal  constituent  ? 


350  INORGANIC     CHEMISTRY. 

meerschaum,  etc. — all  of  which  are  nearly  pure  silicates  of  magnesia.  The 
presence  of  oxyd  of  magnesium  in  rocks  or  minerals  in  considerable  quantity, 
may  be  recognized  by  a  peculiar  slippery  or  greasy  feeling  which  it  imparts 
to  them — hence  the  name  "  soapstone."  Magnesium,  also,  exists  abundantly 
in  all  sea-water,  in  combination  with  chlorine,  iodine,  and  bromine. 

544.  Oxyd  of  Magnesium,  M  g  0  .  —  Calcined  Magnesia.  —  This 
substance,  forming  a  white,  very  light,  bulky  powder,  is  left  when  carbonate 
of  magnesia  is  heated  to  redness.  It  is  much  used  in  medicine  as  a  mild  and 
gentle  aperient. 

645.  Sulphate  of  Magnesia,  MgO,S03,  constitutes  the  well- 
known  purgative  medicine,  Epsom  Salts.  It  is  manufactured  largely  from 
the  bittern,  or  mother-liquor  left  after  the  partial  evaporation  of  sea- water, 
by  the  addition  of  sulphuric  acid  to  the  solution  of  chlorides,  and  also  by  treat- 
ing serpentine  rock  with  sulphuric  acid.  It  possesses  a  bitter,  disgusting 
taste,  and  readily  crystallizes  from  solution  in  small  prismatic  crystals. 

546.  Carbonate  of  Magnesia,  MgO,C 02. — The  common,  white 
magnesia  of  the  shops  is  formed  by  precipitating  a  solution  of  sulphate  of  mag- 
nesia by  a  solution  of  carbonate  of  soda.     It  is  insoluble  in  water,  but  a  solu- 
tion of  carbonic  acid  dissolves  it,  and  forms  the  popular  medicine  known  as 
Murray's  "fluid  magesia."     Carbonate  of  magnesia  also  occurs  as  a  mineral. 

547.  Properties   of   the    Alkaline   Earths,  —  The  alkaline 
earths  are,  next  to  the  alkalies,  the  strongest  chemical  bases.     They  have  a 
caustic  action,  but  far  less  so  than  the  alkalies,  aud  form  with  fats,  soaps 
which  are  insoluble  in  water.     The  carbonates  of  the  alkaline  earths  are  in- 
soluble in  water,  and  when  exposed  to  a  powerful  heat,  part  with  their  car- 
bonic acid — in  this  respect,  being  the  opposite  to  the  carbonates  of  the 
alkalies. 


CHAPTER    XI, 

METALS     OF     THE     EARTHS. 

548.  The  metals  of  the  earths  are,  Aluminum,  Glucin- 
ium, Zirconium,  Thorium,  Yttrium,  Erbium,  Terbium, 
Cerium,  Lantanium,  and  Didymiurn. 

Of  these,  all  but  the  first,  aluminum,  are  extremely  rare,  and  comparatively 
unimportant.  Glucinium  is  the  metallic  base  of  the  earth  glucina,  which  is 
the  characteristic  constituent  of  the  emerald  and  the  beryl.  Zirconium  is  the 
metallic  base  of  the  earth  zirconia,  which  is  found  in  the  gems,  zircon  and 
hyacinth.  The  others  possess  few  points  of  general  interest. 

QTTESTIONS. — "What  is  a  characteristic  of  magnesian  minerals  ?  What  is  calcined  magne- 
sia? What  are  Epsom  salts?  How  are  they  obtained ?  What  is  said  of  carbonate  of 
magnesia  ?  What  are  the  characteristic  properties  of  the  alkaline  earths  ?  What  arc  the 
metals  of  the  earth  ?  What  is  said  of  their  occurrence  in  nature  ? 


ALUMINUM.  351 


SECTION    I. 

ALUMINUM. 

Equivalent,  13'T.     Symbol,  Al.     Specific  gravity,  2*5. 

549.  The  metal  aluminum  was  first  obtained  by  "Wholer,  an  eminent  Ger- 
toan  chemist,  in  1827.     Comparatively  little,  however,  was  known  of  it  until 
within  the  last  few  years,  but  processes  have  been  recently  devised  by  its  dis- 
coverer and  M.  Dcville  of  Paris,  by  which  it  is  obtained,  in  considerable  quan- 
tities, at  a  cost  which  (at  present)  renders  it  about  twice  as  valuable  as  silver. 

Pure  aluminum  is  a  beautiful,  white  metal,  closely  resembling  silver  in  color 
and  hardness.  Its  most  striking  characteristics  are,  that,  while  it  closely  re- 
sembles in  appearance  the  dense,  heavy  metals,  it  is  in  fact  lighter  than  glass ; 
and,  also,  its  power  of  resisting  oxydation — not  tarnishing  by  exposure  to  air 
or  moisture,  or  even  when  heated  to  a  red-heat.  It  fuses  at  a  temperature 
below  the  melting  point  of  silver,  is  malleable,  ductile,  and  remarkably  son- 
orous. Nitric  and  sulphuric  acids,  even  when  concentrated,  scarcely  attack  it 
at  ordinary  temperatures;  but  it  dissolves  freely  in  hydrochloric  acid,  and 
even  in  strong  vinegar  (acetic  acid).  Aluminum  derives  its  name  from  alum, 
into  the  composition  of  which  it  enters. 

The  properties  of  aluminum  are  such  as  to  give  it  a  high  industrial  value ; 
and  it  has  been  applied  to  some  extent  for  economic  purposes. 

550.  Oxyd    of    Aluminum,    Alumina,    A12 03. — This  is  the  only 
known  oxyd  of  aluminum  (a  sesquioxyd).     It  occurs  in  a  state  of  purity, 
with  the  exception  of  a  little  coloring  matter,  in  the  sapphire  and  the  ruby ; 
the  first  of  which  is  blue,  and  the  latter  red.     These  gems  are  only  inferior  in 
hardness,  luster,  and  value,  to  the  diamond.     Emery  (corundum),  which,  from 
its  hardness,  is  so  largely  used  in  grinding  and  polishing,  is  also  nearly  pure 
alumina.     Next  to  silica,  alumina,  in  combination,  is  the  most  abundant  min- 
eral constituent  of  the  crust  of  the  earth. 

By  mixing  a  solution  of  alum  with  an  excess  of  ammonia,  we  obtain  a 
white,  semi-transparent,  bulky  precipitate — hydrate  of  alumina,  AlaOs-f-SHO. 
This,  washed,  dried,  and  strongly  ignited,  furnishes  a  pure  alumina,  ir>  the 
form  of  a  white  powder,  almost  insoluble  in  acids,  and  infusible,  except  be- 
fore the  oxyhydrogen  blow-pipe. 

551.  Alum  , — Common  alum  is  a  combination  of  the  sulphate  of  alumina 
and  the  sulphate  of  potash,  with  24  equivalents  of  water.     The  constitution 
of  this  double  salt  maybe  represented  as  follows:  A1203,  3S03+KO,SOs-h 
24IIO.     When  alum  is  heated,  it  froths  up,  loses  its  water  of  crystallization, 
and  is  converted  into  a  white,  porous  mass,  many  times  the  volume  of  the 
salt  employed ;  in  this  condition  it  is  known  as  anhydrous,  or  burnt  alum. 

Alum  is  occasionally  found  as  a  natural  product  in  the  earth,  but  for  indus- 

QUESTIONS. — What  is  said  of  aluminum  ?  What  are  its  properties  ?  What  is  the  form- 
ula of  alumina  ?  In  what  substances  is  it  found  pure  ?  What  is  said  of  hydrous  and 
anhydrous  alumina  ?  What  is  alum  ?  Give  its  formula  ?  What  is  burnt  alum  ? 


352 


INORGANIC     CHEMISTRY. 


trial  purposes  it  is  manufactured  artificially.  The  sulphate  of  alumina,  which 
enters  into  its  composition,  may  be  obtained  by  dissolving  alumina  from  com- 
mon clay  by  sulphuric  acid,  or  by  exposing  certain  aluminous  (clayey)  slates 
and  shales,  which  contain  sulplmret  of  iron  (iron  pyrites),  to  the  action  of  the 
air,  or  to  a  moderate  heat ;  under  these  circumstances,  the  sulphuret  of  iron 
is  decomposed,  its  sulphur  uniting  with  oxygen  to  form  sulphuric  acid,  which, 
subsequently,  combines  with  the  alumina  of  the  clay  to  form  sulphate  of  al- 
umina. This  salt,  obtained  in  solution  from  the  clay  by  washing,  is  mixed  in 
large  casks  with  sulphate  of  potash,  in  proper  proportions,  and  the  whole  al- 
lowed to  stand.  The  formation  of  alum  immediately  commences,  and  after 
the  lapse  of  a  few  weeks,  the  interior  of  the  cask  becomes  lined  with  a  thick 
mass  of  crystals.  The  staves  of  the  cask  are  then  removed,  and  an  enormous 
mass  of  alum  crystals,  of  the  shape  of  the  cask,  is  left  standing.  (See  Fig. 
189.)  These,  when  drained  and  broken  up,  furnish  alum  ready  for  market. 

FiG.  189. 


Ordinary  alum  has  a  sweetish,  astringent  taste,  and  crystallizes  very  read- 
ily in  regular  octohedrons. 

552.  The  constitution  and  formation  of  alum  affords  a  good  illustration  of 
the  principle  of  isomorphism.  For  example,  we  may  substitute  in  its  manu- 
facture in  the  place  of  sulphate  of  potash,  sulphate  of  soda,  or  sulphate  of  am- 
monia, and  thus  obtain  soda,  or  ammonia  alums,  which  crystallize  in  the 
same  form  as  the  potash  alum,  and  possess  similar  properties ;  or  we  may 

QT7E8TION8.— How  is  alum  manufactured  ?  What  are  its  properties  ?  How  does  the 
constitution  and  formation  of  alum  illustrate  isomorphism  ? 


ALUMINUM.  353 

substitute  in  the  place  of  the  sesqui-oxyd  of  alumina  Al20s,  sesquioxyds  of 
iron,  chromium,  or  manganese,  without  changing  the  original  octohedral, 
crystalline  form.  These  substitutions  will  be  more  clearly  understood  from  an 
examination  of  the  annexed  table  : 

Potash  alum AloOs,  SSOs+KO,  SO3+24HO 

Soda  alum AlsOs,  SSOs+NaO,  SOs+24HO 

Ammonia  alum AlsOs,  3SO3+NH4  O,  SOs+24HO 

Iron  alum FeaOs,  SSOs-fKO,  SOs-f 24HO 

Chrome  alum CraOs,  SSOs+KO,  SO3-1-24HO 

All  these  compounds  are  called  alums,  and  are  said  to  be  isomorphous,  be- 
cause they  possess  a  similar  chemical  constitution,  and  the  same  crystalline 
form.  They  may  be  easily  prepared  by  dissolving  together  in  water  their 
simple  constituent  salts  in  proper  proportions,  and  allowing  the  solution  to 
crystallize.  Potash,  soda,  and  ammonia  alums  are  white,  chrome  alum  a  deep 
purple,  and  iron  alum  a  pale  purple,  or  red. 

Alum,  and  the  compounds  of  alumina  formed  from  it,  are  largely  used  in 
dyeing,  calico  printing,  and  in  tanning.  Alumina  has  a  very  great  attraction 
for  certain  kinds  of  organic  matter,  and  especially  for  coloring  substances. 
To  such  an  extent  is  this  the  case,  that  the  hydrate  of  alumina  is  extensively 
employed  in  the  place  of  animal  charcoal  for  decolorizing  animal  and  vege- 
table solutions.  If  cloth  is  soaked  in  a  solution  of  alumina,  prepared  from 
alum,  a  portion  of  the  earth  attaches  itself  to  the  fibers ;  and  if  subsequently 
plunged  into  a  bath  of  coloring  matter,  it  becomes  permanently  dyed.  Most 
coloring  substances,  without  this  treatment,  would  be  removed  by  washing ; 
but  the  presence  of  alumina  seems  to  serve  as  a  bond  of  union  between  the 
color  and  the  fiber,  which  renders  the  adhesion  of  the  dye  permanent ;  a  few 
other  substances,  such  as  binoxyd  of  tin,  and  the  sesquioxyds  of  chromium 
and  iron,  act  in  the  same  manner,  and  are  called  mordants  (from  the  Latin 
mordeo,  to  bite  in). 

When  alum  is  added  to  a  colored  vegetable  or  animal  solution,  and  the 
alumina  precipitated  by  the  addition  of  an  alkali,  it  carries  down  with  it  the 
greater  portion  of  the  coloring  substance,  and  forms  a  class  of  pigments 
called  lakes.  Carmine  is  a  lake  prepared  in  this  way  from  a  solution  of  co- 
chineal. 

553.  Silicates   of  Alumina , — The  salts  of  silicic  acid  and  alumina 
comprise  a  great  number  of  important  and  interesting  mineral  substances. 

554.  Clay  . — All  the  varieties  of  clay  consist  of  hydrated  silicate  of  alu- 
mina, more  or  less  mixed  with  other  matters  derived  from  the  rocks,  which 
by  their  decomposition  have  formed  clay  ;  such  as  potash,  uncombined  silica, 
oxyd  01'  iron,  lime,  and  magnesia.     According  as  one  or  the  other  of  theso 
ingredients  predominates,  the  character  of  the  clay  and  its  adaptation  to 
specific  purposes  will  vary. 

QUESTIONS. — What  are  the  uses  of  alum  ?  What  property  characterizes  hydrous  alu- 
mina? How  does  alumina  act  in  dyeing ?  What  are  lakes?  What  is  carmine ?  What 
is  clay? 


354  INORGANIC     CHEMISTRY. 

Clays  which  are  nearly  free  from  oxyd  of  iron  or  carbonate  of  lime,  are 
termed  fire-clays,  and  are  used  for  the  manufacture  of  fire-bricks  and  cruci- 
bles ;  such  clays  are  of  rare  occurrence.  Pipe-clay,  used  for  the  manufacture 
of  tobacco-pipes,  is  a  fine  white  clay,  nearly  free  from  iron.  "When  the  pro- 
portion of  carbonate  of  lime  in  a  clay  is  considerable,  it  constitutes  what  is 
known  as  a  marl;  if  the  aluminous  constituent  predominates,  it  forms  an 
aluminous  marl ;  if  the  carbonate  of  lime  be  in  excess,  it  is  a  calcareous 
marl ;  the  latter  is  highly  valued  in  agriculture  as  a  fertilizer  for  light,  sandy 
soils.  Loam  is  a  mixed  substance  containing  much  clay,  some  sand,  iron,  and 
a  varying  proportion  of  organic  matter.  Ochres  are  clays  colored  red  or  yel- 
low by  oxyd  of  iron ;  they  are  extensively  used  as  paints.  Fuller's  earth  is  a 
porous  silicate  of  alumina,  which  has  a  strong  adhesion  to  oily  matters ;  if 
made  into  a  paste  with  water,  and  allowed  to  dry  upon  a  spot  of  grease  on 
a  board  or  cloth,  it  removes  most  of  the  oil  by  capillary  attraction.  It  owes 
its  name  to  the  fact  that  it  is  employed  to  remove  the  grease  applied  to  wool 
in  spinning. 

555.  Clay  emits  a  peculiar  odor  when  breathed  upon,  which  is  known  as 
an  argillaceous  odor.     "When  mixed  with  a  soil,  it  gives  it  firmness  and  con- 
sistency, and  retains  the  moisture,  ammonia,  carbonic  acid,  and  organic  mat- 
ters which  contribute  to  the  support  of  plants.     In  this  way  it  indirectly 
ministers  to  the  wants  of  vegetation,  although  alumina  itself  is  not  known  to 
enter  as  a  constituent  into  the  structure  of  either  plants  or  animals. 

Among  other  important  minerals  of  which  silicate  of  alumina  is  a  prin- 
cipal constituent,  may  be  mentioned  feldspar,  mica,  all  the  varieties  of  slates, 
and  lavas,  trap,  basalt,  porphyry,  etc.  The  gems,  topaz  and  garnet,  are  also 
in  great  part  silicate  of  alumina. 

The  beautiful  artificial  blue  pigment  known  as  ultramarine  consists  mainly 
of  silicate  of  alumina  fused  with  sulphide  of  sodium. 

556.  General   Properties   of  the    Earths . — The  earths  are 
entirely  insoluble  in  water,  and  do  not  combine  with  carbonic  acid.     They 
possess  weak  basic  properties,  and  alumina  in  some  instances  may  even  act 
the  part  of  an  acid.     The  metals  of  the  alkalies,  the  alkaline  earths,  and  the 
earths,  are  all  of  a  low  specific  gravity,  and  are  sometimes  called,  on  this  ac- 
count, the  light  metals,  to  distinguish  them  from  the  other  metals,  which  are 
dense  and  heavy. 

QUESTIONS. — What  is  fire-clay  ?  What  is  pipe-clay  ?  "What  are  marls  ?  What  is  loam  ? 
What  are  ochres  ?  What  is  "  fuller's  earth  ?"  What  are  the  properties  of  clay  ?  What 
minerals  are  mainly  composed  of  silicate  of  alumina  ?  What  is  ultramarine  ?  What  are 
the  general  properties  of  the  earths  ? 


GLASS    AND    POTTERY,  355 

CHAPTER    XII. 

GLASS     AND     POTTERY. 

557.  Glass  is  a  compound  substance  produced  by  fusing 
together,  by  a  high  and  long-continued  heat,  mixtures  of 
the  silicates  of  potash,  soda,  lirne,  magnesia,  alumina  and 
lead — the  nature  and  proportions  of  the  ingredients  vary- 
ing according  to  the  purpose  for  which  the  glass  is  to  be 
used. 

Silica  fused  with  the  alkalies,  potash,  or  soda,  readily  yields  a  transparent 
glass  of  easy  fusibility,  but  not  adapted  for  economic  purposes,  since  it  is  un- 
able to  resist  the  action  of  water  and  acids.  If  the  proportions  are  3  of  al- 
kali to  1  of  silica,  the  compound  is  so  readily  soluble  in  water  as  to  be 
designated  as  "  soluble  glass."  (§  414.)  By  increasing  the  proportion  of 
silica,  we  can  greatly  dimmish  the  solubility  of  the  alkaline  silicates,  but 
not  entirely  so  On  the  other  hand,  silica  fused  with  lime,  magnesia, 
baryta,  or  alumina,  yields  compounds  which  resemble  porcelain  rather  than 
glass,  are  entirely  insoluble,  and  melt  at  only  a  high  temperature.  No  single 
silicate  is,  therefore,  adapted  by  itself  to  form  glass,  but  by  judicious  mix- 
ture of  the  various  silicates  we  can  contain  compounds  which  are  transparent, 
free  from  color,  fusible  at  a  moderate  heat,  and  insoluble  in  water.* 

The  temperature  at  which  glass  fuses  depends  upon  the  amount  of  silica  it 
contains ;  the  greater  the  proportion,  the  less  the  fusibility. 

558.  The  principal  varieties  of  glass  are  as  follows: — 

Common,  colorless,  or  white  glass,  which  is  used  for  making  tumblers,  win- 
dow-glass, and  looking-glasses,  is  a  compound  of  silicate  of  potassa  or  soda, 
with  silicate  of  lime.  The  character  of  the  glass,  however,  varies  very  much 
according  as  one  or  the  other  of  the  alkalies  is  used.  Glass  composed  of  sim- 
ply the  silicates  of  potash  and  lime,  is  exceedingly  transparent,  very  hard,  and 
of  difficult  fusibility.  It  is  highly  prized  in  the  laboratory  for  its  adaptation  to 
certain  chemical  requirements.  The  celebrated  Bohemian  glass — the  finest 

*  In  strictness,  the  best-made  glass  is  to  a  certain  extent  soluble.  If  very  finely-pow- 
dered window-glass  be  placed  on  turmeric  paper,  and  moistened,  it  will  exhibit  an  alkaline 
reaction.  Windows  in  old  houses  often  show  prismatic  colors,  owing  to  the  circumstance, 
that  the  long-continued  action  of  rain  and  moisture  has" washed  out  the  alkali  of  the  glass, 
and  left  an  irregular  condition  of  surface,  which  occasions  a  refraction  of  light.  Specimens 
of  ancient  glass  which  have  been  dug  out  of  the  earth,  often  exhibit  a  pearly  luster,  re- 
sulting from  pure  silica,  the  alkali  having  been  slowly  removed  by  long  exposure  to 
damp. 

QUESTIONS.— What  is  glass  ?  Why  is  a  mixture  of  silicates  necessary  for  the  formation 
of  durable  glass?  What  is  said  of  the  fusibility  of  glass?  What  is  the  composition  of 
common  white  glass  ?  What  is  the  character  of  potash-glass  ?  What  is  Bohemian  glass  t 


356  INORGANIC     CHEMISTRY. 

glass  produced,  is  a  silicate  of  potash  and  lime,  with  a  little  silicate  of  alum- 
ina. By  substituting  soda  in  the  place  of  potash,  we  obtain  a  more  fusible, 
but  a  less  transparent  glass ;  varieties  of  glass  with  this  composition,  are 
known  as  "  crown  glass,"  plate-glass,  window-glass,  etc.  The  presence  of 
soda  in  glass  imparts  to  it  a  blueish-green  tinge,  which  is  not  observed  when 
potash  alone  is  used. 

Green  Bottle  Glass,  and  other  inferior  desciptions  of  glass  used 
for  the  manufacture  of  articles  in  which  color  is  not  regarded,  consist  of  an 
alkali,  silica,  lime,  and  alumina;  the  cheapest  and  most  ordinary  materials 
being  used,  such  as  wood-ashes  and  common  salt,  as  alkaline  products,  com- 
mon sand,  clay,  gas-lime,  and  the  refuse  lime  and  alkali  left  after  the  manu- 
facture of  soap.  The  green  color  of  bottle-glass  is  due  mainly  to  the  presence 
of  oxyds  of  iron  and  manganese. 

Flint-Glass,  so  called  from  the  circumstance,  that  the  silica  used  in 
its  manufacture  was  formerly  derived  from  pulverized  flints,  is  a  mixture  of 
silicate  of  potash  and  silicate  of  the  oxyd  of  lead.  It  fuses  at  a  lower  temper- 
ature than  the  ordinary  varieties  of  glass,  has  a  beautiful  transparency,  and  a 
comparative  softness,  which  enables  it  to  be  cut  and  polished  with  ease. 
Glass  which  contains  lead  possesses  the  property  of  refracting  light  in  a  re- 
markable manner,  and  is  consequently  employed  for  the  construction  of 
lenses  for  optical  instruments,  glass  prisms,  chandelier-drops,  etc. ;  it  is,  also, 
the  basis  of  the  artificial  gems  known  as  paste,  which  are  colored  by  metallic 
oxyds. 

559.  The  silica  used  for  the  manufacture  of  fine  glass  is  generally  in  the 
form  of  pure  white  sand,  entirely  free  from  oxyd  of  iron.  Such  sand  is  by  no 
means  common,  the  finest  in  the  world  being  at  present  found  among  the 
Green  Mountains  of  Western  Massachusetts,  from  which  localities  large  quan- 
tities are  annually  exported  to  Europe.  The  silica  of  the  Bohemian  glass  is 
obtained  by  pulverizing  masses  of  pure  white  quartz.  The  alkali  used  is  a 
refined  carbonate  of  potash  or  soda.  These  two  ingredients,  with  a  proper 
proportion  of  air-slacked  lime,  or  oxyd  of  lead,  are  thoroughly  mixed,  and 
fused  in  large  crucibles  of  refractory  fire-clay,  in  a  circular  reverberatory  fur- 
nace. This  furnace  is  usually  in  the  form  of  a  truncated  cone,  60  to  80  feet 
high,  and  40  to  50  feet  in  diameter  at  the  base.  The  furnace  is  at  the  center 
of  the  cone,  and  the  glass-pots,  to  the  number  of  4  to  10,  are  arranged  around 
the  circumference,  and  opposite  to  openings  in  the  walls  of  the  furnace.  Fig. 
190  represents  the  exterior  of  the  furnace,  and  the  general  appearance  of  a 
glass-house. 

The  fire  of  a  glass  furnace  is  never  allowed  to  slacken,  and  the  melting-pots 
remain  permanently  in  their  situations  for  several  months,  being  charged  from 
the  exterior.  A  heat  of  about  forty-eight  hours  is  requisite  to  convert  the 
crude  materials  into  a  liquid,  homogeneous  glass. 

QUESTIONS.— What  is  the  character  of  soda-glass  ?  What  is  the  composition  of  green 
bottle-glass  ?  What  is  flint-glass  ?  In  what  form  is  the  silica  used  in  the  manufacture  of 
glass?  What  its  alkali  ?  How  is  glass  formed  ? 


GLASS    AND    POTTEKY. 


35T 


The  details  of  the  working  and  molding  of  glass  are  purely  mechanical,  and 
a  description  of  them  is  foreign  to  the  object  of  this  work. 

560.  Colored  Glass  • — Glass  is  colored  by  the  addition  to  it,  in  a  fused 
state,  of  small  quantities  of  the  metallic  oxyds,  which  dissolve  in  it  without 


FIG  190 


affecting  its  transparency.  Thus,  oxyd  of  cobalt  imparts  a  deep  blue  ;  oxyd 
of  manganese,  a  purple  or  violet ;  oxyd  of  copper,  a  green ;  oxyds  of  iron,  a 
dull  green  or  brown ;  and  oxyd  of  gold,  a  ruby  or  rose  color.* 


*  Cut-glass  ornamental  artices,  which  exhibit  different  colors  upon  the  same  specimen, 
and  at  different  depths  in  the  thickness  of  the  glass,  are  manufactured  in  the  following 
manner :  the  object  is  first  formed  in  white,  transparent,  and  colorless  glass ;  then,  being 
allowed  to  cool  until  it  acquires  solidity  and  consistency,  it  is  dipped  for  a  moment  in  a 
pot  of  colored  glass  in  a  state  of  fusion,  and  being  suddenly  withdrawn,  it  carries  away 
upon  it  a  thin  coating  of  colored  glass,  which  immediately  hardens  upon  it,  and  become8 
incorporated  with  it.  The  article  is  then  shaped  by  the  processes  of  the  glass-maker,  and 
if  it  be  afterwards  cut,  those  parts  which  are  cut  will  disclose  the  clear,  transparent  glass, 
while  the  parts  not  cut  remain  coated  with  the  color.  It  is  by  this  process  that  all  the  effects 

QUESTION.— How  is  glass  colored  ? 


358  INOKGANIC    CHEMISTRY. 

561.  Enamel  is  a  term  given  to  glass  which  is  rendered  milk-white 
opaque  by  the  addition  of  binoxyd  of  tin.  Examples  of  such  enamels  are  to 
be  seen  in  watch-dials,  and  in  the  so-called  porcelain  transparencies.  Colored 
enamels  are  produced  by  the  addition  of  metallic  oxyds  to  white  enamels. 

662.  Annealing  . — If  glass  be  allowed  to  cool  suddenly  after  fusion,  it 
becomes  exceedingly  brittle,  and  articles  made  from  it  are  liable  to  break  in 
pieces  from  the  least  scratch  or  jar,  or  even  from  a  slight  but  sudden  change 
of  temperature,  as  when  transferred  from  a  cold  to  a  warm  room. 

This  property  is  strikingly  illustrated  by  what  are  called  Prince  Rupert's 
drops,  which  are  little  pear-shaped  masses  of  glass,  formed  by 
FIG.  191.      dropping  melted  glass  into  cold  water.    (See  Fig.  191.)     These 
^^*~     may  be  subjected,  without  breaking,  to  considerable  pressure, 
/f  or  even  to  a  smart  stroke,  but  if  the  little  end  of  the  drop  be 

/  jl  nipped  off,  the  whole  mass  instantly  flies  in  pieces  with  a  sort 

ty^  of  explosion,  and  is  converted  into  powder.     This  effect  ap- 

pears to  be  due  to  the  fact,  that  the  particles  of  which  these 
little  masses  are  composed,  are  in  a  state  of  unequal  tension,  owing  to  the 
formation  of  a  solid  coating  upon  the  exterior,  while  the  interior  parts  are  still 
fluid ;  the  latter  being  thereby  prevented  from  expanding,  as  they  become 
solid.  The  drops  will  bear  a  concussion  because  the  mass  then  vibrates  as  a 
whole,  but  if  the  end  be  broken,  a  vibratory  movement  is  communicated 
along  the  surface  without  reaching  the  internal  parts ;  this  allows  them  some 
expansion,  which  overcomes  the  cohesion  of  the  outer  coating,  and  the  whole 
at  once  flies  in  pieces.  To  obviate,  therefore,  this  tendency  to  brittleness,  all 
glass  articles,  after  their  manufacture,  are  subjected  to  the  operation  of  an- 
nealing, which  is  a  very  slow  and  gradual  process  of  cooling,  by  which  the 
parts  are  enabled  to  assume  their  natural  position  with  regard  to  each  other. 
In  some  cases,  several  days,  or  even  weeks,  are  required  for  the  cooling  of 
particular  articles. 

563.  Pottery  and  Porcelain,— The  basis  of  all  earthen- 
ware, porcelain,  and  china,  is  silicate  of  alumina  (clay) . 

Pure  silicate  of  alumina,  however,  contracts  greatly  and  unequally  on  dry- 
ing, and,  consequently,  is  unfitted  to  be  used  by  itself  for  fictile  purposes: 
This  difficulty  is,  however,  overcome  by  the  addition  to  the  clay  of  a  propor- 
tion of  silica,  and  to  compensate  for  a  loss  of  tenacity  in  the  clay  thereby  oc- 
casioned, it  is  also  customary  to  incorporate  with  the  mass  some  fusible 
material,  as  an  alkali,  silicate  of  lime,  etc.,  which,  at  the  temperature  required 
for  baking  the  ware,  fuses,  becomes  absorbed  by  the  more  infusible  portion, 

which  are  seen  in  ornamental  articles,  which  consist  partially  of  colored,  and  partially  of 
clear  glass,  are  produced.  Additional  colors  may  also  be  combined  on  the  article  in  the 
same  manner,  and  by  cutting  a  surface  so  coated,  to  different  depths,  varieties  of  effects 
may  be  produced,  involving  a  display  of  two  or  more  colors. 

QUESTIONS. — What  are  enamels?  What  effect  is  produced  by  allowing  glass  to  cool 
suddenly?  How  is  this  illustrated  by  Prince  Rupert's  drops?  What  is  annealing? 
What  is  tho  baiiia  of  all  earthenware  ?  Why  can  not  pure  clay  be  used  alon«  ? 


GLASS    AND    POTTERY.  359 

and  binds  the  whole,  on  cooling,  into  a  solid  mass.  According  to  the  greater 
or  less  proportion  of  these  fusible  materials,  the  ware  is  more  or  less  transpa- 
rent, or  resembles  glass  in  a  greater  or  less  degree. 

564.  Porcelain  is  the  name  applied  to  the  finest  varieties  of  earthen- 
ware. It  is  composed  of  a  very  pure,  white  clay,  called  "  kaolin"  (derived 
from  the  decomposition  of  feldspar),  very  finely-divided  silica,  prepared  by 
crushing  and  grinding  calcined  flints,  and  a  little  lime.  The  utmost  pains 
are  taken  to  thoroughly  incorporate  these  ingredients,  and  to  avoid  the  intro- 
duction of  particles  of  grit,  or  other  foreign  bodies.  The  mixture,  having  the 
consistency  and  appearance  of  dough,  is  then  fashioned  upon  a  peculiar  kind 
of  lathe — called  a  "  potter's  wheel,"— or  in  molds  of  plaster  of  Paris,  into  ware, 
— dried,  and  baked  in  a  kiln  or  oven  for  a  period  of  about  40  hours.  The  por- 
celain in  this  condition  is  technically  termed  biscuit,  and  is  compact  and  solid, 
but  so  porous  as  to  readily  imbibe  water,  and  even  allow  it  to  filter  through 
its  substance.  This  difficulty  is  remedied  by  covering  the  ware  with  a  glassy 
coating  called  a  glaze,  which  generally  consists  of  a  more  fusible  mixture  of 
the  same  materials  as  the  porcelain  itself.  These,  in  a  state  of  fine  powder, 
are  made  into  a  cream  with  water,  and  into  this  the  ware  is  dipped  for  a  mo- 
ment, and  then  withdrawn ;  the  water  sinks  into  its  substance,  leaving  the 
powder  evenly  spread  upon  the  surface,  which,  when  submitted  to  a  moder- 
ate heat,  fuses,  and  forms  a  uniform,  vitreous  coating.  In  ornamented  porce- 
lain, the  designs  are  printed  or  painted  upon  the  surface  with  various  metallic 
oxyds,  which  develope  •  their  colors  only  after  fusion  with  the  ingredients  of 
the  glaze. 

The  material  called  "Parian,"  of  which  statuettes,  etc.,  are  manufactured, 
is  a  carefully-prepared  variety  of  porcelain.  . 

The  details  of  the  manufacture  of  the  ordinary  varieties  of  "  stone"  and 
"  earthen"  ware,  are  in  principle  the  same  as  those  involved  in  the  manufac- 
ture of  porcelain,  less  care,  however,  being  taken  in  the  selection  of  materials, 
and  less  labor  being  bestowed  upon  their  preparation.  The  coarser  kinds  of 
earthenware  are .  sometimes  covered  with  a  yellowish-white  glaze,  of  which 
oxyd  of  lead  is  an  important  ingredient.  The  use  of  such  vessels  in  culinary 
operations  is  highly  objectionable,  inasmuch  as  the  lead  is  liable  to  be  dis- 
solved off  by  acids,  and  act  as  a  poison. 

Bricks  and  common  pottery- ware  owe  their  red  color  to  the  iron  naturally 
contained  in  the  clay  of  which  they  are  composed,  which,  by  heating,  is  con- 
verted into  red  oxyd  of  iron.  Some  varieties  of  clay,  like  that  found  near 
Chicago,  contains  little  or  no  iron ;  and,  consequently,  the  bricks  made  from 
it  are  all  light-colored. 

QUESTIONS. — What  is  the  composition  of  porcelain?  Describe  its  manufacture.  How- 
is  porcelain  ornamented  with  colored  figures?  What  is  "Parian?"  How  does  the 
manufacture  of  earthenware  differ  from  porcelain?  How  is  earthenware  sometimes 
glazed  ?  Why  is  the  use  of  vessels  glazed  with  lead  dangerous?  Why  are  bricks  and 
flower-pots  red  ? 


360  INORGANIC     CHEMISTRY. 

CHAPTER     XIII. 

THE     COMMON,     OR     HEAVY    METALS. 

SECTION    I. 

IRON   (Ferrum). 

Equivalent,  28.     Symbol,  Fe.     Specific  gravity,  7*8. 

565.  Natural  History  and  Distribution,— Iron   is  the 
most  abundant,  the  most  widely  diffused,  and  the  most 
useful  of  all  the  metals.     It  is  the  only  metal  which  enters 
into  the  structure  of  all  the  vertebrate  animals,  as  an  es- 
sential constituent  (existing  always  in  the  blood),  and  the 
only  one  whose  oxyds  are  not  injurious  to  either  animals 
or  plants. 

Iron  in  a  metallic  and  malleable  state,  alloyed  with  nickel,  cobalt,  and  small 
quantities  of  other  metals,  is  found  upon  the  surface  of  the  earth  in  large 
masses  of  meteoric  origin.  These  masses  are  so  peculiar  in  their  composition 
and  structure,  and  differ  so  essentially  from  all  terrestrial  substances,  that 
although  they  may  not  have  been  seen  to  fall,  they  are  easily  recognized. 
Some  of  these  extraordinary  bodies  are  from  15  to  20  tons  weight;  one  ob- 
served to  fall  from  the  atmosphere  in  an  ignited  state  in  South  America  in 
1844,  was  upward  of  a  cubic  yard  in  dimensions.  A  specimen  in  the  cabinet 
of  Yale  College  weighs  1,635  Ibs.,  and  one  in  the  Smithsonian  Institution, 
252  Ibs.  The  occurrence  in  nature  of  metallic  iron  of  a  terrestrial  origin  is 
exceedingly  rare.  It  is,  however,  said  to  be  occasionally  found  associated 
with  ores  of  platinum,  and  also  in  little  nodules  inclosed  in  masses  of  iron  ore 
— the  latter  being  evidently  the  result  of  electro-galvanic  agency.  Recent  in- 
vestigations by  Hayes  of  Boston  have  also  rendered  it  probable  that  a  deposit 
of  native  iron  exists  on  the  West  Coast  of  Africa,  in  the  vicinity  of  Liberia. 

Iron  in  a  state  of  perfect  purity  is  not  found  also  as  an  article  of  com- 
merce— the  very  best  artificial  irons  always  containing  some  carbon,  and 
generally  minute  quantities  of  silica,  sulphur,  and  phosphorus.  Chemically 
pure  iron  may,  however,  be  obtained  by  reducing  the  pure  peroxyd  of  iron 
at  a  red-heat  by  a  current  of  hydrogen  gas. 

566.  Compounds    of    Iron    with    Oxygen , — Iron  forms  three 
definite  compounds  with  oxygen:   1.  Protoxyd,  FeO ;   2.  Sesquioxyd,  com- 
monly called    the   peroxyd,  Fe^Os ;    3.  Ferric  acid,  Fe03.      Another  oxyd, 
Fe304,  found  native  in  large  quantities,  and  known  as  the  black,  or  magnetic 
oxyd  of  iron,  is  by  some  regarded  as  a  distinct  oxyd,  and  by  others  as  a  com- 
pound of  protoxyd  and  sesquioxyd. 

QUESTIONS.— What  is  said  of  iron  ?  Is  malleable  iron  found  in  nature  ?  Is  the  iron  of 
commerce  pure  ?  How  may  chemically  pure  iron  be  obtained  ?  What  are  the  compound* 
of  iron  and  oxygen  * 


IRON.  361 

567.  Protoxyd  of  Iron,  FeO,  does  not  occur  in  nature  except  in 
combination.  It  is  a  powerful  base,  and  unites  with  the  acids  to  form  salts 
which  have  a,  greenish  color  and  a  styptic  taste — properties  which  are  pos- 
sessed in  a  very  marked  degree  by  green  vitriol,  which  is  a  sulphate  of  the 
proloxyd  of  iron,  Protoxyd  of  iron  may  be  easily  obtained  in  the  form  of  a 
hydrate,  by  dissolving  pure  sulphate  of  iron  in  water  recently  boiled  and 
adding  an  alkali  to  the  solution.  The  bulky  precipitated  hydrate  is  at  first 
nearly  white,  but  absorbing  oxygen  from,  the  air,  it  soon  becomes  brown,  and 
finally  red,  from  its  conversion  into  sesquioxyd.  In  a  moist  state,  this  hy- 
drate constitutes  the  most  effectual  antidote  in  poisoning  by  arsenic. 

5G8.  Sesquioxyd  of  Iron,  F  e203,  Peroxyd, — is  found  native  ia 
great  abundance,  and  constitutes  some  of  the  most  valuable  of  the  ores  of 
iron.  It  is  in  this  state  of  oxydation  that  iron  is  generally  found  in  soils  and 
minerals,  assuming  oftentimes  a  deep  red  color  (red  oxyd)  as  in  ocher,  burnt 
clay,  etc.  The  substance  called  rouge,  crocus,  or  colcothar,  used  for  polishing 
glass  or  metals,  is  this  oxyd  in  a  state  of  fine  powder,  prepared  by  igniting 
the  sulphate  of  iron. 

569.  Black,  or  Magnetic  Oxyd  oflron,  F  e304,  occurs  abun- 
dantly in  nature,  constituting  the  common  magnetic  iron  ore,  and  the  native 
loadstone,  both  which  acquire  magnetic  properties  from  the  inductive  influ- 
ence of  the  earth.  It  is  also  the  principal  constituent  of  the  scales  of  oxyd 
which  are  detached  during  the  forging  of  wrought-iron. 

670.  Ferric  Acid,  F  e  Os,  may  be  formed  by  heating  I  part  of  peroxyd 
of  iron  with  4  parts  of  saltpeter  to  full  redness  for  aa  hour,  in  a  covered  cru- 
cible. A  brown  mass  is  thus  obtained — ferrate  of  potash — which  digested 
with  water  yields  a  beautiful  violet-colored  solution. 

571.  0  r  €  s  of  Iron  . — The  ores  of  iron  are  extremely  numerous.  The 
following  are  some  of  the  most  valuable:  FKJ.  192. 

1.  The  magnetic,  or  blade  oxyd,  which 
has  a  black  color  and  a  metallic  luster. 
It  is  found  in  beds  in  the  primitive 
rocks,  and  sometimes  constitutes  entire 
mountains,  as  the  iron-mountains  of 
Missouri  It  is  one  of  the  richest  of  the 
ores  of  iron,  and  contains  about  70  per 
cent  of  pure  iron.  The  superior  iron 
of  Sweden  and  Russia  is  prepared  from 
it.  The  specular  iron,  or  red  iron  ore, 
consists  mainly  of  sesquioxyd  of  iron ; 
under  this  class  are  included  the  ores  known  as  red  and  brown  hematites,  and 
bog-iron  ore.  Red  hematite  often  occurs  in  fibrous  crystallized  nodules, 
forming  beautiful  cabinet  specimens.  (See  Fig.  192.)  All  the  ores  of  this 


QUESTIONS. — What  is  said  of  the  protoxyd  ?  How  may  it  be  prepared  ?  What  is  said 
of  the  sesquioxyd  ?  What  is  rouge  ?  What  is  said  of  the  black  oxyd  ?  What  of  ferric 
acid  ?  What  are  the  principal  ores  of  iron  ? 

16 


362  INORGANIC    CHEMISTRY. 

class  yield  reddish  brown  powders,  and  may  thus  be  distinguished  from  the 
black  oxyd ; — they  contain  about  G3  per  cent,  of  iron  ;  3.  Clay -iron  stone  is 
an  impure  carbonate  of  iron,  mingled  with  varying  proportions  of  clay,  lime, 
magnesia,  and  manganese.  This  ore  occurs  extensively  associated  with  coal, 
and  contains  about  33  per  cent,  of  metallic  ircn  •  it  is  the  chief  source  of  the 
enormous  quantity  of  iron  manufactured  in  Great  Britain.  All  clays  which 
are  capable  of  yielding  20  per  cent,  of  iron  are  called  ores. 

572.  Bi-Sulphuret  of  Iron,  Fe  S2, — iron  pyrites, — although  a  very 
abundant  mineral,  is  not  used  as  a  source  of  metallic  iron ;  it  occurs  iu  cu- 
FiG  193  bical   crystals   (see  Fig.   193)    and    fibrous 

radiated  masses  ;  from  its  "bright  yellow  color 
and  metallic  luster  it  is  often  mistaken  for 
gold  (fool's  gold),  but  its  character  may  be 
easily  determined  by  the  sulphurous  odor 
which  it  evolves  by  heating. 

573.  Pr'oto  sulphate  of  Iron, 
F  e  0 ,  S  Or-f-7  HO.—  Copperas  ;  Green  Vit- 
riol.— This  salt  may  be  readily  formed  by  dis- 
solving metallic  iron  in  sulphuric  acid,  but 
for  commercial  purposes  it  is  prepared  on  a 
very  large  scale  by  exposing  iron  pyrites  to  the  action  of  a  r  and  moisture, — 
the  sulphuret  of  iron,  by  the  absorption  of  oxygen,  yielding  sulphuric  acid 
and  oxyd  of  iron.  The  salt  produced  is  then  dissolved  out  with  water,  and 
the  solution  allowed  to  crystallize.  In  this  way  it  is  prepared  in  great  quan- 
tities at  Stafford,  Yermont. 

Copperas  forms  beautiful,  transparent,  bluish-green  crystals,  which  effloresce 
in  dry  air,  and  become  covered  with  brownish-white  crust.  In  combination 
with  certain  astringent  vegetable  matters,  as  tannin,  extract  of  galls,  etc.,  it 
forms  permanent  black  dyes,  and  is  hence  much  used  in  the  arts  for  dye- 
ing, and  for  the  manufacture  of  inks. 

574.  Iron  is  employed  in  the  arts  in  three  different  states,  viz,  as  crude, 
or  cast  iron,  as  wrought,  or  malleable  iron,  and  as  steel. 

575.  Cast    Iron,  the  metal  obtained  by  smelting  the  ore  with  carbon, 
is  a  chemical  compound  of  iron  and  carbon — a  carbide,  or  carburet  of  iron, 
containing  also,   as  impurities,  small  quantities  of  uncombined  carbon  and 
silicon,  and  generally  some  phosphorus,  sulphur,  aluminum,  and  calcium.     It 
is  fusible  at  a  glowing  white-heat,  is  brittle,  and  can  neither  be  forged  or 
welded.     The  proportion  of  carbon  in  different  varieties  of  cast-iron  varies, 
but  in  no  instance  does  it  exceed  5  per  cent.     The  proportion  of  silica  varies 
from  3-5  to  0-25  per  cent. 

In  commerce,  two  varieties  of  cast-iron  are  recognized,  viz.,  white  and 
gray  metal.  The  former  contains  more  carbon,  and  is  harder,  more  brittle, 

QUESTIONS. — What  are  iron  pyrites?  "What  is  copperas ?  Howis  it  prepared  ?  What 
are  its  uses  ?  In  what  three  conditions  is  iron  employed  in  the  arts  ?  What  is  cast-iron  ? 
What  two  varieties  are  recognized  ?  What  are  their  respective  properties  ? 


IRON. 


363 


and  more  fusible  than  the  latter.  It  is  also  characterized  by  a  silvery  white- 
ness, and  a  lamelar  crystalline  fracture.  Gray  metal,  on  the  contrary,  is  very 
soft,  dark  in  color,  and  of  a  granular  texture ;  it  admits  of  being  filed  and 
drilled  with  ease,  which  white  metal  does  not.  If  white  iron  be  melted  and 
allowed  to  cool  very  gradually,  a  portion  of  its  carbon  crystallizes  out  as 
graphite,  and  gray  cast-iron  is  produced.  The  gray  metal  is  best  adapted  for 
castings,  and  the  white  for  the  manufacture  of  bar  iron  and  steel 

576.  Smelting    of   Iron . — The  operation  of  smelting  iron,  or  the 


FIG.  194. 


reduction  of  its  ores  to  a  metallic  state,  is  ef- 
fected through  the  agency  of  the  blast-fur- 
nace, which  is  a  tall,  chimney -like  structure, 
constructed  of  stone  in  a  conical  form,  and 
lined  upon  the  interior  with  the  most  refrac- 
tory fire-brick.  Its  internal  cavity,  repre- 
sented in  section  in  Fig.  194,  resembles  in 
shape  a  long,  narrow  funnel,  inverted  upon 
the  mouth  of  another  shorter  funnel,  and  is 
divided  into  the  central  portion,  &,  called  the 
shaft ;  the  boshes,  e,  or  the  part  of  the  ftir- 
nace  sloping  inward ;  the  crucible,  t,  and  the 
hearth,  h.  The  top,  or  mouth  of  the  furnace 
serves  both  for  charging  it,  and  for  the  es- 
cape of  gases.  A  steady  and  intense  heat  is 
maintained  by  means  of  strong  blasts  of  air 
driven  into  the  furnace  by  powerful  blowing 
apparatus  through  a  number  of  blast-pipes, 
or  tuyeres,  a  a,  at  its  base.  The  amount  of 
air  thus  supplied  exceeds,  in  some  large  furnaces,  12,000  cubic  feet  per  min- 
ute.  It  was  formerly  the  practice  to  use  the  air  at  ordinary  temperatures 
(cold  blast),  but  within  a  comparatively  recent  period  the  production  of  iron 
has  been  very  greatly  cheapened  and  increased  by  heating  the  air  to  a  tem- 
perature of  about  500°  F.  before  it  enters  the  furnace  (hot-blast). 

At  the  commencement  of  operations,  the  furnace  is  first  heated  with  coal 
only,  for  about  24  hours,  in  order  to  raise  it  to  the  proper  temperattare ;  but 
when  working  regularly,  it  is  charged  alternately  with  coal  and  a  mixture  of 
ore  and  limestone  broken  into  small  pieces,  until  it  is  completely  filled  with 
successive  layers  of  fuel  and  of  ore.  The  ore  before  smelting  is  generally 
roasted,  or  heated  separately,  in  order  to  expel  from  it  water  and  carbonic 
acid,  and  render  it  dry  and  porous.  The  limestone  added  serves  as  flux — 
that  is,  it  renders  the  silica,  clay,  and  other  foreign  matters  associated  with 
the  ore  readily  fusible — forming  a  dark-colored  glass  termed  "  slag."  As 
soon  as  the  ore  has  become  thoroughly  ignited,  its  oxygen  unites  with  the 
carbon  of  the  fuel  to  form  carbonic  oxyd,  while  the  metal  fuses,  and  together 
with  the  slag  flows  down  to  the  bottom  of  the  furnace.  Here  the  slag,  being 

QUESTIONS. — Describe  the  construction  of  a  blast-furnace?  How  is  iron  reduced  from 
the  ore  ?  Why  is  limestone  used  ia  the  smelting  of  iron  ? 


364  INORGANIC     CHEMISTRY. 

the  lightest,  floats  upon  the  top  of  the  melted  metal,  and  from  time  to  time 
is  raked  off  through  apertures  contrived  for  the  purpose— the  iron  being 
drawn  off  by  openings  at  a  lower  level.  As  the  contents  of  the  furnace  are 
removed  from  below,  or  consumed,  fresh  materials  are  supplied  from  above, 
so  that  the  process  of  smelting  goes  on  uninterruptedly,  day  and  night,  for 
years,  or  until  the  furnace  requires  repair.  The  melted  iron  drawn  off  from 
the  blast  furnace  is  run  into  rude  molds  of  sand,  and  when  solidified  consti- 
tutes crude  cast-iron,  or  the  pig-iron  of  commerce. 

577.  Malleable,  or  Bar  Iron,  is  cast-iron  deprived  of 
its  carbon  and  other  impurities.  It  is  not  fusible  at  a 
white  heat,  and  may  be  forged  and  welded. 

The  manufacture  of  bar-iron,  or  the  purification  of  the  crude  pig-iron,  is  ef- 
fected by  exposing  cast-metal  to  the  regulated  action  of  oxygen  at  a  high 
temperature,  whereby  the  carbon,  and  other  oxydizible  impurities  which  it 
contains,  are  burnt  out  of  it,  and  the  iron  left  pure.  The  details  of  the  process 
are  essentially  as  follows : — the  crude  pig-iron  is  first  remelted  and  suddenly 
cooled,  by  which  it  loses  a  part  of  its  carbon  and  silica,  and  is  rendered  white, 

FIG.  195. 


crystalline,  and  exceedingly  hard.  In  this  state  it  is  known  as  fine  metal* 
Broken  into  fragments,  it  is  next  introduced  in  charges  of  about  500  Ibs.  weight, 
into  a  kind  of  reverberatory  furnace,  called  a  puddling  furnace,  and  again 
melted.  The  workmen  then,  by  means  of  long  iron  bars,  stir  up  (puddle)  the 
fused  mass,  and  thoroughly  expose  it  to  the  influence  of  the  heated  air  circu- 
lating above  it.  (See  Fig.  195.)  As  the  operation  proceeds,  the  metal  passes 
from  a  liquid  to  a  pasty  condition,  emits  blue  flames  (carbonic  oxyd),  gradu- 
ally grows  tough  and  less  plastic,  and  finally  becomes  pulverulent.  At  this 
point  the  heat  is  raised  to  the  highest  intensity,  and  air  is  carefully  excluded 

QUESTIONS — What  is  malleable  or  bar-iron  ?    What  is  the  principle  of  its  preparation  f 
Describe  the  first  step  of  the  process  ?    What  is  puddling  ? 


IRON.  365 

by  closing  the  furnace.  After  a  time,  the  metal  softens  sufficiently  to  enable 
the  puddler  to  collect  it  in  balls  (called  blooms),  upon  the  end  of  an  iron  bar, 
which  are  then  withdrawn  from  the  furnace,  and  subjected,  while  in  a  state 
of  intense  heat,  to  the  action  of  a  massive  hammer,  moved  by  machinery.  A 
melted  slag  (silicate  of  the  oxyd  of  iron)  is  thus  forcibly  squeezed  out  of  the 
metal,  and  the  particles  of  iron  are  brought  nearer  to  each  other.  The  iron  is 
then  fashioned  into  a  bar,  by  passing  it  between  grooved  rollers ;  and  the  bar 
thus  obtained  is  cut  into  lengths,  piled  up  in  a  reverberatory  furnace,  reheated 
and  re-rolled.  .  For  the  best  qualities  of  iron,  this  process  of  doubling  upon 
itself,  reheating  and  re-rolling,  is  repeated  several  times,  in  order  to  render  the 
fibers  of  the  iron  parallel  to  each  other — an  arrangement  which  greatly  in- 
creases the  tenacity  of  the  metal.  These  operations,  when  properly  per- 
formed, free  the  iron  from  all  but  mere  traces  of  the  impurities  contained  in 
the  crude  metal.  The  complete  separation,  however,  of  phosphorus  and  sul- 
phur, when  present,  is  a  matter  of  great  difficulty ;  and  these  two  elements, 
above  all  others,  are  the  most  injurious  to  iron — rendering  it  brittle  and 
rotten.* 

578.  Malleable  Iron  Castings . — Small  articles  of  cast-iron,  such 
as  stirrups,  bits,  door- latches,  etc.,  may  be  rendered  malleable  in  a  degree,  by 
closely  packing  them  in  powdered  hematite  (peroxyd  of  iron)  in  tight  fire- 
brick cases,  and  subjecting  them  to  a  red  heat,  in  what  is  called  an  annealing 
furnace,  for  a  period  of  time  varying  from  six  to  ten  days,  finally  allowing 
them  to  cool  slowly.  In  this  case,  the  character  of  the  iron  is  changed,  by 
a  removal  of  a  part  of  its  carbon,  through  the  agency  of  the  oxygen  of  the 
powdered  hematite.f 

579.  Steel  is  a  chemical  compound  of  carbon  and  iron — 
a  carburet  or  carbide  of  iron — containing,  however,  a  much 
less  proportion  of  carbon  than  cast-iron. 

The  quantity  of  carbon  in  good  steel  varies  between  0'7  and  1*7  per  cent ; 
but  steel  which  possesses  the  greatest  tenacity,  has  been  found  to  contain 
from  1*3  to  1*5  per  cent,  of  carbon,  and  about  01  of  silicon. 

"What  is  called  Natural  Steel  is  produced  directly  from  the  best  cast-iron 

*  The  presence  in  bar-iron  of  (V033  per  cent,  of  sulphur,  is  sufficient  to  destroy  its  prop- 
erty of  welding,  and  render  it  brittle  when  hot.  Such  iron  is  termed  "  hot  short."  Iron, 
on  the  contrary,  which  contains  phosphorus,  may  be  readily  forged  and  welded  when  hot, 
but  breaks  when  cold ;  it  is  accordingly  known  as  "  cold  short"  The  discovery  of  a 
ready  method  of  effectually  separating  these  two  elements  from  iron,  is  regarded  as  one 
of  the  great  problems  of  chemical  science  which  yet  remains  unsolved. 

t  Sheet-iron  is  bar-iron  rolled  while  hot  to  the  requisite  degree  of  thinness.  It  is  a  very 
popular  notion,  that  the  so-called  "  Russian  sheet-iron"  is  manufactured  in  Russia  by  a 
secret  process ;  but  such  is  not  the  case.  The  iron  in  question  is,  in  the  first  instance,  a 
very  pure  article,  rendered  exeedingly  tough  and  flexible  by  refining  and  annealing.  Its 
bright,  glossy  surface  is  partially  a  silicate  and  partially  an  oxyd  of  iron,  produced  by  pass- 
ing the  hot  sheet,  moistened  with  a  solution  of  wood-ashes,  through  polished  steel  rollers. 

QUESTIONS.— What  are  malleable  iron  castings  ?  What  is  steel  ?  What  is  the  percent- 
age of  carbon  in  steel  ?  How  is  natural  steel  produced  ? 


INORGANIC    CHEMISTRY. 

by  exposing  it.  in  a  melted  condition  on  the  hearth  of  a  furnace,  to  the  action 
of  a  current  of  air ;  the  oxygen  of  the  air  burns  off  a  portion  of  the  carbon 
from  the  cast-iron,  and  steel  remains.  The  preparation  of  natural  steel,  there- 
fore, is  an  intermediate  stage  in  the  conversion  of  wrought  into  cast-iron. 
Steel  thus  obtained  is  of  an  inferior  quality,  and  is  used  for  making  cheap 
and  coarse  instruments.  The  best  qualities  of  steel  are  obtained  by  a  process 
called  cementation,  which  is  an  operation  just  the  reverse  of  that  by  which 
natural  steel  is  formed.  It  consists  in  imbedding  bars  of  the  best  refined  mal- 
leable iron  in  powdered  charcoal  contained  in  large  boxes  of  fire-brick  in  such 
a  way  that  all  access  of  air  from  without  is  entirely  excluded.  The  boxes 
are  then  subjected,  in  a  furnace,  to  a  most  intense  heat,  for  a  period  varying 
from  five  to  ten  days,  during  which  time  the  carbon  of  the  charcoal  completely 
penetrates  the  mass  of  the  iron,  and  converts  it  into  steel.  The  steel,  when 
withdrawn,  has  a  peculiar,  rough,  blistered  appearance,  and  is  hence  known 
as  blistered  steel.  Small  bars  of  blistered  steel,  made  into  faggots  and  welded 
together,  at  a  high  temperature,  under  a  tilting,  or  trip  hammer,  forms  "  tilted 
steel;"  this,  broken  up,  reheated,  and  re-welded,  forms  "  shear  steel,"  so  called, 
because  it  was  originally  thus  prepared  for  making  shears  to  dress  woollen 
cloth.  The  quality  of  the  steel  is  greatly  improved  by  these  successive  pro- 
cesses of  reheating  and  re-hammering.  Cast  steel  is  prepared  by  melting 
blistered  steel,  casting  it  into  ingots,  and  then  drawing  it  into  bars  under  the 
hammer ;  it  is  the  most  perfect  variety  of  steel,  and  is  employed  for  all  fine 
cutlery. 

Case-hardening  . — It  is  sometimes  desirable  to  convert  articles 
manufactured  from  soft  iron  .superficially  into  steel ;  this  is  termed  case- 
hardening,  and  is  usually  performed  by  heating  them  for  a  short  time  in 
contact  with  powdered  charcoal,  or  sprinkling  their  surfaces  when  red-hot 
•with  powdered  ferrocyanide  of  potassium. 

580.  The  chemical  changes  which  take  place  in  the  conversion  of  bar-iron 
into  steel  are  obscure,  and  it  is  somewhat  doubtful  whether  we  yet  fully  un- 
derstand the  exact  composition  of  steel.  The  most  recent  researches  seem  to 
indicate  that  nitrogen  is  a  constituent  of  all  steel,  and  that  its  presence,  to- 
gether with  carbon,  is  essential  to  its  formation.  The  finest  steel  known, 
called  "Wootz,  is  produced  in  a  very  rude  way  by  the  natives  of  India,  and  is 
used  for  the  manufacture  of  the  celebrated  sword-blades  of  the  East.  The 
most  experienced  English  manufacturers  are  unable,  with  all  their  resources, 
to  produce  steel  of  an  equal  quality,  and  its  peculiar  excellence  has  been  at- 
tributed by  Professor  Faraday  to  the  presence  in  its  composition  of  a  small 
quantity  of  aluminum.* 

*  Some  authorities  have  supposed  that  carbon  is  contained  in  steel  in  the  form  of  the 
diamond,  since  it  seems  almost  impossible  to  refer  the  great  differences  which  exist  be- 
tween cast-iron  and  steel  to  merely  a  minute  variation  of  the  proportions  of  the  combined 

QUESTIONS— How  is  the  best  steel  obtained  ?  What  are  the  different  varieties  of  steel  ? 
What  is  cast-steel  ?  What  is  case-hardening  ?  What  is  said  of  our  knowledge  of  the 
formation  and  composition  of  steel  ? 


MANGANESE  —  CHROMIUM.  367 

581.  Properties  of  Steel . — Steel  Is  less  fusible  than  cast-iron, 
and  more  so  than  bar-iron.  Its  most  remarkable  property  consists  in  its 
power  of  assuming  a  hardness  scarcely  inferior  to  that  of  the  diamond  by 
heating  to  redness  and  then  suddenly  cooling  by  immersion  in  cold  water; 
by  this  treatment  it  is  also  rendered  extremely  brittle  and  almost  perfectly 
elastic.  By  reheating  the  steel  and  allowing  it  to  cool  slowly,  it  again  be- 
comes nearly  as  soft  as  ordinary  iron,  and  between  these  two  extremes  any 
required  degree  of  hardness  may  be  attained.  In  working  steel,  the  articles 
are  first  finished  in  a  soft  state,  and  afterward  hardened ;  they  are  then  tem- 
pered, or  raised  to  such  a  temperature  as  is  requisite  to  give  them  the  degree 
of  softness  and  elasticity  required.  The  workman  easily  estimates  this  tem- 
perature by  observing  the  color  of  the  thin  film  of  oxyd  which  appears  upon 
the  surface.  Thus,  a  light  straw  color  indicates  the  degree  of  heat  requi- 
site for  tempering  razors;  a  deep  yellow,  that  suitable  for  scissors,  pen- 
knives, etc. ;  while  sword-blades,  watch-springs,  and  instruments  demanding 
great  elasticity,  must  be  exposed  to  a  much  higher  degree  of  heat,  or  until 
their  surfaces  acquire  a  deep  blue  color.  These  various  changes  in  the  color 
of  steel  may  be  illustrated  by  heating  a  polished  steel  knitting-needle  in  the 
flamo  of  a  spirit-lamp. 

SECTION    II. 

MANGANESE  AND  CHROMIUM. 

582.  Manganese,— Equivalent,  27'6;  Symbol,  Mn  ;  Spe- 
cific gravity,  8.— Metallic  manganese  is  a  grayish-white 
metal,  resembling  some  varieties  of  cast-iron. 

It  is  extremely  brittle,  and  so  hard  that  it  is  not  scratched  by  a  file ;  a 
fragment  set  at  a  sharp  angle  may  be  even  substituted  in  the  place  of  the 
diamond  for  cutting  glass.  It  is  susceptible  of  a  very  high  polish,  and  at  or- 
dinary temperatures  in  the  air*  is  not  readily  oxydized.  It  dissolves  easily 
in  acids.  No  practical  application  has  ever  been  made  of  this  metal,  and 
previous  to  its  investigation  by  Brunner  ia  1857,  very  erroneous  ideas  of  its 
properties  were  generally  entertained.  It  is  now  believed  to  possess  a  high 
economic  value,  especially  as  an  element  of  certain  alloys.  Its  preparation 
is,  however,  difficult. 

Manganese  is  not  found  in  nature  as  a  metal,  but  as  an  oxyd  it  is  very 
widely  diffused  in  the  mineral  kingdom.  Traces  of  it  are  very  frequently 

carbon.  In  accordance  with  this  view,  a  theory  has  been  proposed,  that  the  fine  cutting 
properties  of  a  steel  blade  are  due  to  a  minute  form  of  diamond  imbedded  in  the  edge; 
and  that  the  benefit  of  dipping  a  razor  into  hot  water  before  using  is  owing  to  the  circum- 
stance that  the  metal  is  thereby  expanded,  forcing  the  sharp  edges  of  the  embedded  car- 
bon crystals  into  such  positions,  that  they  cut  with  greater  facility . 

QUESTIONS. — What  are  the  properties  of  steel  ?  What  is  understood  by  the  tempering 
of  steel  ?  What  is  the  appearance  of  metallic  manganese  ?  What  are  its  properties  ? 
What  is  said  of  its  distribution  in  nature  ? 


368  INORGANIC     CHEMISTRY. 

found  in  the  ashes  of  plant?,  and  in  river  and  lake  waters.  The  dark,  metal- 
lic-like  discoloration  which  may  be  often  noticed  on  stones  and  pebbles  in 
the  beds  of  streams  flowing  over  igneous  rocks,  is  due  in  great  part  to  a 
coating  of  oxyd  of  manganese  deposited  from  the  water.  The  most  impor- 
tant and  valuable  ore  of  manganese  is  the  black  oxyd,  also  known  as  the 
peroxyd,  or  binoxyd,  Mn02.  It  is  found  abundantly  at  Bennington,  Vermont, 
and  in  many  other  localities  in  the  United  States. 

Seven  different  oxyds  of  manganese  are  described,  the  two  highest  of  which 
possess  acid  properties,  and  are  termed  manganic  and  permanganic  acids. 
Manganic  acid  is  known  only  in  combination  with  potash,  with  which  it  forms 
a  salt — manganate  of  potash — possessing  some  very  curious  properties.  It  is 
best  prepared  by  intimately  mixing  4  parts  of  finely-powdered  peroxyd  of 
manganese  with  3^-  parts  of  chlorate  of  potash ;  5  parts  of  hydrate  of  potash 
dissolved  in  a  small  quantity  of  water,  are  then  added  to  the  mixture,  which 
evaporated  to  dryness  and  heated  to  dull  redness,  for  an  hour  in  an  earthen 
crucible,  yields  a  dark  green  mass.  This  dissolved  in  water,  gives  at  first 
an  emerald-green  solution,  but  the  color  almost  immediately  and  successively 
changes  to  dark-green,  blue,  purple,  and  finally  to  crimson.  These  changes 
of  color  are  occasioned  by  a  decomposition  of  manganate  of  potash,  which  is 
hence  often  called  chameleon  mineral;  the  final  red  color  retained  by  the  so- 
lution is  due  to  the  formation  of  permanganic  acid,  which  is  comparatively  a 
stable  compound. 

The  salts  of  manganese  are  characterized  by  a  delicate  rose-color,  which  is 
especially  noticeable  in  crystals  of  the  sulphate.  The  chief  uses  of  the  com- 
pounds of  manganese  are  chemical,  the  black  oxyd  being  extensively  employed 
to  decompose  muriatic  acid,  and  furnish  chlorine  (§  350) ;  it  likewise  supplies 
the  chemist  with  his  cheapest  source  of  oxygen,  and  is  used  as  a  coloring 
material  in  the  manufacture  of  glass  and  enamels. — MILLER. 

583.  Muomi um, —Equivalent,  26'4  ;  Symbol,  Or. — Chro- 
mium is  found  only  as  an  oxyd  in  .nature.,  and  although 
abundant  in  some  localities,  is  very  sparingly  distributed 
over  the  earth.  The  metal  itself,  which  is  obtained  with 
difficulty,  is  grayisliTwhite,  brittle,  and  so  extremely  hard, 
that  it  resists  the  action  of  the  strongest  acids. 

The  most  abundant  ore  of  chromiunij  is  a  compound  of  protoxyd  of  iron 
and  sesquioxyd  of  chromium, — known  as  "  chrome  iron."  It  is  found  more 
abundantly  in  the  United  States  than  elsewhere,  especially  in  the  vicinity 
of  Baltimore,  and  at  Lancaster,  in  Pennsylvania. 

Almost  all  the  compounds  of  chromium  are  characterized  by  very  beautiful 
colors,  and  are  hence  highly  valued  in  the  arts  as  materials  for  paints,  for 

QUESTIONS. — What  is  its  principal  ore?  What  is  said  of  its  compounds  with  oxygen? 
What  peculiar  properties  does  the  manganate  of  potash  possess.?  What  are  the  proper- 
ties of  chromium  f  What  is  its  principal  ore  2  For  what  arc  the  compoundaof  chromium 
remarkable  ? 


MANGANESE  —  CHROMIUM.  369 

dyeing  fabrics,  and  for  coloring  glass,  porcelain,  enamels,  etc,  Oxyd  of 
chromium  is  the  coloring  ingredient  of  the  emerald,  of  the  green  varieties  of 
serpentine,  and  probably  also  of  the  ruby. 

Chromium  is  prepared  for  use  in  the  arts  by  fusing  the  pulverized  ore, 
chrome  iron,  with  nitrate  of  potash  (saltpeter) ;  by  this  treatment  the  chro- 
mium absorbs  oxygen  and  becomes  converted  into  an  acid — chromic  acid — 
which  unites  with  the  potash  of  the  niter  to  form  a  yellow  salt,  the  chromate 
of  potash,  KOjCrOg.  By  adding  sulphuric  acid  to  a  solution  of  chromate 
of  potash,  we  remove  one  half  the  base  and  form  a  new  salt — bi-chromate 
of  potash,  KO,  2O03 — which  crystallizes  in  beautiful  red  tables,  and  furnishes 
the  source  from  whence  most  of  the  other  compounds  of  chromium  are  pre- 
pared, It  is  also  in  the  form  of  this  salt  that  chromium  is  best  known  as  an 
article  of  commerce. 

584.  Chromate    of    Lead,     P  b  0  ,  C  r  03,  —  Chrome    Yellow.  — By 
adding  a  solution  of  bi-chromate  of  potash  to  a  solution  of  acetate  of  lead,  we 
obtain  a  beautiful  yellow  precipitate  of  chromate  of  lead ;  this,  washed  and 
dried,  constitutes  the  well-known  pigment,  chrome  yellow.     By  mixing  chrome 
yellow  with  white  substances,  such  as  chalk,  clay,  etc.,  numerous  other  shades 
of  yellow  are  obtained,  as  Paris  yellow,  king's  yellow,  etc. ;  but  by  mixing  it 
with  Prussian  blue,  a  variety  of  cheap  green  pigments  are  formed,  as  Naples 
green,  olive  green,  etc. 

585.  Chromic    Acid,    CrOg,  is  readily  prepared  by  mixing  4  mea- 
sures of  a  cold  saturated  solution  of  bi-chromate  of  potash  with  5  of  oil  of  vit- 
riol ;  as  the  liquid  cools,  chromic  acid  is  deposited  in  the  form  of  beautiful 
crimson  needles.     The  mother  liquor  is  then  poured  off,  and  the  crystals 
allowed  to  dry  on  a  porous  brick,  closely  covered  with  a  bell  glass ;  since  they 
decompose  instantly  by  contact  with  organic  matter.     "When  chromic  acid  is 
brought  in  contact  with  alcohol  or  ether,  it  imparts  to  these  substances  a  por- 
tion of  its  oxyyen,  and  the  intensity  of  the  chemical  action  occasioned,  pro- 
duces an  immediate  ignition.     This  may  be  illustrated  by  projecting  a  small 
quantity  of  chromic  acid  upon  a  little  alcohol  or  ether  contained  in  a  tum- 
bler. 

If  we  mix  in  a  small  mortar  as  much  chromic  acid  as  can  be  taken  upon 
the  point  of  a  knife,  with  about  one  quarter  as  much  of  powdered  camphor 
(without  pressing  upon  it  strongly),  and  then  let  fall  into  the  mortar  a  few 
drops  of  alcohol  from  a  considerable  height,  instantaneous  ignition  and  de- 
flagration ensues — like  the  burning  of  gunpowder.  The  residue  in  the  mortar, 
after  the  decomposition,  is  sesquioxyd  of  chromium,  which  presents  the  appear- 
ance of  an  elegant  green,  mossy  vegetation. — STOCKHART, 

QUESTIONS.— How  is  it  prepared  for  use  in  the  arts?  What  is  the  composition  of  bi- 
chromate of  potash  ?  What  is  chrome  yellow  ?  How  is  chromic  acid  prepared  ?  What 
are  its  properties  ? 

16* 


370  INORGANIC     CHEMISTRY. 


SECTION    III. 

COBALT     AND     NICKEL. 

586.  Cobalt,— Equivalent,  29'5,  Symbol,  Co.— Cobalt  is 
a  reddish-gray  metal,  which  is  never  found  in  nature  in  a 
metallic  state,  except  as  a  constituent,  in  small  propor- 
tions, of  meteoric  iron. 

Oxyd  of  cobalt  is  remarkable  for  the  magnificent  blue  color  it  communicates 
to  glass,  and  also  to  porcelain.  This  may  be  illustrated  by  moistening  a  small 
bead  of  borax  glass  with  a  solution  of  nitrate  of  cobalt,  and  then  fusing  it  in 
the  flame  of  a  blow-pipe.  The  substance  called  smalt  is  a  glass,  colored  blue 
by  oxyd  of  cobalt,  and  then  finely  pulverized ;  it  was  formerly  much  used  as 
a  pigment,  especially  in  the  manufacture  of  blue  writing-paper ;  but  is  now 
almost  entirely  superseded  by  the  cheaper  ultramarine. 

587.  Sympathetic  Inks , — The  chloride  of  cobalt,  CoCl,  is  easily  ob- 
tained by  dissolving  oxyd  of  cobalt  in  hydrochloric  acid  ;  the  solution,  evapor- 
ated to  small  bulk,  yields  ruby-red  crystals,  which  are  freely  soluble  in  water. 
The  liquid  resulting  from  their  aqueous  solution,  is  of  a  deep-blue  color  when 
concentrated,  but  when  diluted,  is  pink,     In  this  latter  condition  it.may  be 
Used  as  a  sympathetic  ink :  characters  written  on  paper  with  it  are  invisible, 
from  their  paleness  of  color,  until  the  salt  has  been  rendered  anhydrous  by 
exposure  to  heat,  when  the  letters  appear  blue.     When  the  paper  is  laid 
aside,  moisture  is  again  absorbed  by  it,  and  the  writing  once  more  disappears. 

588.  Nickel.— Equivalent,  2W  ;  Symbol,  Ni.— Nickel  is 
a  brilliant,  silver-white  metal,  extremely  ductile,  and  more 
fusible  than  iron.     It  occurs  in  nature  associated  chiefly 
with  arsenic,  sulphur,  and  cobalt ;  but  its  ores  are  by  no 
means  abundant.     It  is  almost  always  found  native  in  me- 
teoric iron,  sometimes  in  a  proportion  of  10  per  cent. 

The  Baits  of  nickel  are  of  a  delicate  green  color,  both  when  in  a  solid  state 
and  when  in  solution. 

The  chief  use  of  nickel  is  in  the  manufacture  of  German  silver,  which  is  a 
white,  malleable  alloy,  consisting,  in  100  parts,  of  51  parts  of  copper,  30'6  of 
zinc,  and  18 '4  of  nickel— the  latter  element  imparting  to  the  alloy,  when  pol- 
ished, a  silver-like  appearance. 

589.  General    Properties  of    Cobalt  and  1H  c  k  e  1  .—These 
two  metals  are  especially  remarkable  from  the  circumstance,  that  they  almost 


QUESTIONS.— What  is  said  of  metallic  cobalt?  What  are  the  characteristics  of  oxyd 
of  cobalt?  What  is  smalt?  What  is  sympathetic  ink?  What  is  said  of  the  properties 
and  distribution  of  nickel  ?  What  of  its  salts  ?  What  of  its  uses  ?  What  is  German 
silver  ?  In  what  respects  do  cobalt  and  nickel  resemble  each  other  ? 


ZINC . — C  A  D  M  I  U  M .  371 

always  occur  associated  together  in  nature,  have  nearly  the  same  chemical 
equivalent,  and  agree  very  closely  in  their  chemical  properties.  They  are 
also  the  only  metals  beside  iron  which  are  readily  susceptible  of  magnetism. 

SECTION     IY. 

ZINC     AND     CADMIUM 

590.  Zinc,  —  Equivalent,  32*5  ;  symbol,  Zn  ;  specific 
gravity,  6*8  to  7. — Zinc  is  not  found  native,  but  its  ores 
are  somewhat  abundant. 

The  most  important  of  its  ores  are  the  carbonate  of  zinc,  called  calamine ; 
the  red-oxyd  of  zinc,  found  in  great  purity  and  quantity  at  Sterling,  New 
Jersey ;  and  a  sulphide  of  zinc,  called  blende — the  latter  being  usually  associ- 
ated with  ores  of  lead. 

591.  Proper  tie  s. — Zinc  is  a  hard,  bluish- white  metal,  which  exhibits 
a  crystalline  fracture  when  broken.     It   is  brittle  at  ordinary  temperatures, 
but  between  200°  and  300°  F.  acquires  considerable  malleability  and  duc- 
tility, and  may  be  rolled  and  wrought  with  ease  ;  it  is  a  very  singular  fact 
that  zinc  so  treated  retains  its  malleability  when  cold,  and  it  is  in  this  way 
that  the  ordinary  sheet-zinc  of  commerce  is  manufactured.     At  a  temperature 
of  400°  it  again  becomes  so  brittle  as  to  admit  of  being  pulverized  in  a  mor- 
tar.    At  770°  it  melts,  and  at  a  bright  red  heat  it  is  volatilized.     If  its  vapor 
be  brought  in  contact  with  air,  it  burns  with  a  splendid  green  light,  and  is 
converted  into  oxyd,   which  falls  in  copious  white  flakes,   anciently  called 
"  philosopher's  wool"     Zinc,   when  exposed  to  a  moist  atmosphere,  soon 
tarnishes,  and  becomes  covered  with  a  thin  film  of  oxyd,  which  protects  the 
metal  beneath  from  any  further  change.     This  property  renders  zinc  valuable 
for  a  great  variety  of  economic  purposes. 

By  reason  of  the  volatility  of  zinc  at  high  temperatures,  it  is  reduced  from  its 
ores  by  a  process  of  distillation  rather  than  smelting.  This  is  effected  by  heat- 
ing a  mixture  of  pulverized  ore  and  coal  in  earthen  retorts,  and  condensing 
the  evolved  vapors  over  water,  or  in  receivers  from  whence  free  access  of  air 
is  excluded.  The  zinc  of  commerce  always  contains  impurities,  generally 
iron  and  lead,  and  sometimes  arsenic. 

592.  Galvanized  Iron  is  sheet-iron  coated  with  zinc.   It  is  prepared  as 
follows :  the  iron  is  first  immersed  in  dilute  sulphuric  acid,  to  remove  all  scale 
or  oxyd  from  its  surface,  and  then  plunged  into  a  bath  of  molten  zinc,  cov- 
ered with  sal-ammoniac.     The  use  of  the  latter  substance  is  to  dissolve  off 
an}*-  adhering  film  of  oxyd  from  the  iron,  as  a  complete  union  of  the  two 
metals  will  not  occur  unless  the  surface  of  the  iron  is  chemically  clean.    The 
thin  coating  of  zinc  which  adheres  to  the  iron  renders  the  latter  metal  nega- 
tively electric,  and  prevents  its  oxydation  or  rusting.     (§  247.) 

QTTESTIONB. — What  is  said  of  the  distribution  and  ores  of  zinc  ?  What  are  the  proper- 
ties of  zinc  ?  How  is  zinc  reduced  from  its  ores  ?  What  is  galvanized  iron  1 


372  INORGANIC     CHEMISTRY.       . 

593.  Oxyd    of   Zinc,    ZnO . — Zinc  White. — Zinc  forms  only  one  com- 
pound with  oxygen,   which,  when  pure,  is  a  white  powder.     Mixed  with 
drying  oils,  it  is  much  employed  as  a  white  paintr  under  the  name  of  zinc- 
white,  as  a  substitute  for  white  lead ;  it  wants,  however,  the  opacity  and  dead 
whiteness  for  which  white  lead  is  so  much  valued ;  but  has  the  advantage 
of  not  blackening  by  the  action  of  sulphuretted  hydrogen,  and  of  not  being 
deleterious  to  the  health  of  the  workmen.* 

Sulphate  of  zinc,  ZnO,S03,  constitutes  the  white  vitriol  of  commerce;  it 
used  medicinally  in  small  doses,  and  also  in  the  operations  of  calico  printing. 
The  salts  of  zinc  are  colorless,  and  act  powerfully  and  rapidly  as  emetics. 

594.  Cadmium,    Cd,isa  white  metal,  resembling  tin  in  appearance, 
but  allied  to  zinc  in  its  properties.     It  is  usually  found  in  very  small  quanti- 
ties accompanying  the  ores  of  zinc,  and  has  no  practical  value  in.  the  arts. 


SECTION    Y. 

LEAD     AND     TIN. 

595.  1  6  ad. — Equivalent,  103*5  ;  Symbol,  Pb  (Plumbum);  Specific  gravity, 

11  '44. — Lead  is  rarely  found  native,  but  its  oresare  most  abun- 

FlG.  196.         dant.  Almost  all  the  lead  of  commerce  is.  obtained  fr6m  galena, 

r N    or  the  sulphide  of  lead,  PbS,  an  ore  which  occurs  in  bouud- 

'  ^  less  profusion  in  the  United  States,  especially  in  Missouri. 
The  reduction  of  the  metal  is  easily  effected  by  crushing  the 
ore  and  subjecting  it  to  a  moderate  heat  in  a  reverberatory 
furnace.  Galena  always  contains  a  proportion  of  silver, 
which  is  sometimes  so  abundant  that  the  ore  is  worked  for 
this  metal  rather  than  for  the  lead.  "When  the  galena  oc- 
curs in  bold,  well-characterized  cubes  (see  Fig.  19-6),  the  contained  lead  is 


*  Zinc-white  Is  at  present  extensively  manufactured  from  the  red  zinc  ore  found  aft 
Sterling,  New  Jersey,  by  an  exceedingly  interesting  and  simple  process.  The  ore,  pul- 
verized and  mixed  with  coal,  is  heated  in  large  oven-shaped  retorts  of  brick,  to  each  of 
which  a  wide  pipe  of  sheet-iron  is  fitted  ;  these  extend  through  the  furnace  wall  and  con- 
nect with  a  very  large  horizontal  tube,  through  which  a  current  of  air  is  kept  moving  by 
the  revolution  of  a  fan-wheeL  The  current  thus  formed  flows  first  thro-agh  the  retorts, 
and  burns  the  vapor  of  zinc  to  oxyd  ;  which  is  immediately  transported  by  the  draft  of 
air  through  the  continuation  of  the  tube  to  a  chamber,  where  it  falls  as  delicate  powder. 

Oxyd  of  zinc,  in  combination  with  chloride  of  zinc,  has  recently  been  applied  to  pro- 
ducing a  lustrous  hard  finish  to  the  walls  of  rooms,  in  the  place  of  plaster  of  Paris.  A 
coat  of  oxyd  of  zinc  mixed  with  size,  and  made  up  like  a  wash,  is  first  laid  on  the  wall, 
ceiling,  or  wainscot,  and  over  that  a  coat  of  chloride  of  zinc  applied,  being-  prepared  fn 
the  same  way  as  the  first  Trash,  The  oxyd  and  chloride  effect  an  immediate  combination, 
and  form  a  kind  of  cement,  smooth  and  polished  as  glass. 


QUESTIONS.— What  is  said  of  oxyd  of  zinc  ?  How  is  it  prepared  ?  "What  is  said  of  sul- 
phate of  zinc  ?  What  of  cadmium  ?  Whaffis  said  of  the  distribution  of  lead  ?  What  is 
galena?  What  is  a  usual  constituent  of  this  ore? 


LEAD. —  TIN.  373 

usually  nearly  pure  ;  but  a  mineral  which  will  yield  0'36  per  cent,  of  silver, 
or  120  ounces  to  the  ton,  is  considered  extremely  rich.* 

596.  Properties . — Lead  is  a  soil,  bluish-gray  metal,  which  may  be 
rolled  into  tolerably  thin  sheets,  or  drawn  into  wire  ;  its  tenachy,  however,  is 
very  feeble.     It  fuses  at  620°  F.,  and  contracts  considerably  at  the  moment 
of  its  solidification,  which  circumstance  renders  it  unsuitable  for  castings.     At 
a  temperature  above  red-heat  it  is  somewhat  volatile 

The  surface  of  a  piece  of  lead,  when  freshly  cut,  presents  a  high  metallic 
luster,  but  it  soon  tarnishes  by  exposure  to  the  air,  owing  to  the  formation  of 
a  thin,  closely-adherent  film  of  oxyd,  which  protects  the  metal  from  further 
change.  In  a  perfectly  dry  atmosphere,  lead  undergoes  no  alteration,  and 
even  when  sealed  up  in  a  vessel  of  pure  water,  free  from  air,  the  metal  will 
retain  its  brilliancy  for  an  indefinite  period  ;  but  if  it  be  exposed  to  the  united 
action  of  air  and  pure  water,  it  is  subject  to  a  powerful  corrosion. — MILLER. 

597.  Lead,  when  taken  into  the  system  in  any  soluble  form,  is  a  dangerous 
poison ;  its  effects,  moreover,  do  not  generally  manifest  themselves  immedi- 
ately, but  the  poison  accumulates,  and  produces,  often  after  the  lapse  of  years, 
a  number  of  different  and  distressing  forms  of  disease,  such  as  colic,  paralysis, 
etc.     The  action  of  water  on  lead  is,  therefore,  a  matter  of  great  importance 
in  a  sanitary  point  of  view,  since  this  metal  is  extensively  employed  in  cis- 
terns and  pipes,  for  the  storage  and  supply  of  water. 

The  action  of  different  waters  on  lead  varies  considerably.  Waters  which 
are  very  pure  and  highly  aerated — waters  which  contain  nitrates,  chlorides,  or 
organic  matter,  as  those  flowing  from  the  vicinity  of  barn-yards,  manure 
heaps,  or  from  swamps  and  fields,  all  dissolve  lead  from  the  pipes  through 
which  they  pass;  and  the  constant  use  of  such  waters, in  the  process  of  time, 
will  introduce  sufficient  lead  into  the  system  to  produce  disease.  Waters,  on 
the  other  hand,  which  contain  sulphates,  carbonates,  and  phosphates,  exert 
but  comparatively  little  action  on  lead.  Bi-carbonate  of  lime  is  especially  re- 
markable for  the  preservative  influence  which  it  exerts ;  and  as  this  salt  is  a 
very  common  impurity  in  water,  few  spring  waters  act  on  lead  to  a  dangerous 
extent.  In  these  cases,  a  film  of  insoluble  carbonate,  sulphate,  or  phos- 
phate of  lead,  is  formed  upon  the  surface  of  the  pipe,  and  all  further  corrosion 
prevented.  Rain-water,  as  collected  from  the  roofs  of  houses,  is  for  the  most 
part  sufficiently  impure,  especially  in  cities,  to  prevent  its  action  on  lead.  So 
general,  however,  is  the  action  of  water  upon  lead,  that  it  is  rare  to  find  any 


*  So  small  a  quantity  of  silver  as  three  or  four  ounces  to  a  ton  of  lead,  maybe  ex- 
tracted profitably  by  a  process  devised  by  Mr.  Pattinson,  of  England.  It  consists  in 
melting  the  argentiferous  lead,  and  allowing  It  to  cool  slowly.  Under  these  circumstances, 
the  lead  tends  to  separate  in  the  form  of  crystals  of  pure  metal,  before  the  alloy  of  silver 
has  been  cooled  sufficiently  to  solidify.  By  a  careful  regulation  of  temperature,  the  great 
mass  of  the  lead  may,  therefore,  be  removed  mechanically,  leaving  the  silver  concentrated 
in  a  small  bulk  of  alloy. 

QUESTION^. — What  are  the  properties  of  lead  ?  What  changes  does  lead  undergo  in  the 
air?  What  is  said  of  the  poisonous  inflaence  of  lead?  What  of  the  action  of  Crater  on 
lead  ?  What  salts  arrest  the  action  of  water  on  lead  ?  How  do  they  effect  this  2 


374  INORGANIC    CHEMISTRY. 

water  that  has  been  kept  in  contact  with  this  metal  for  a  considerable  period, 
which  does  not  contain  some  traces  of  it.  Stone  and  wooden  cisterns,  and 
tin,  iron,  or  wood  pipes,  are  therefore,  greatly  to  be  preferred  to  lead.  Where 
lead  service-pipes  are  used,  it  is  always  advisable  to  allow  the  water  to  run 
for  some  time  before  using. 

598.  Oxyds   of  Lead  . — Four  distinct  oxyds  of  lead  are  recognized,  the 
most  important  of  which  are  the  protoxyd,  PbO,  and  the  peroxyd,  Pb02. 

P  r  o  t  o_xj  d  of  Lead,  Litharge,  Massicot,  PbO,  is  a  yellow  powder, 
usually  obtained  on  a  large  scale,  by  the  oxydation  of  molten  lead  in  a  cur- 
rent of  air.  Its  production  may  be  illustrated  by  fusing  a  small  piece  of  lead 
on  charcoal,  before  the  exterior  flame  of  a  blow-pipe.  The  melted  lead  oxyd- 
ating,  is  at  first  converted  into  a  grayish  powder — a  mixture  of  oxyd  of  lead 
and  metallic  lead— but  by  continued  blowing,  the  grav  color  is  changed  into  a 
brilliant  yellow  —litharge.  This  oxyd  of  lead  is  a  powerful  base,  and  is  ex- 
tensively used  in  the  arts,  especially  in  the  glazing  of  pottery  and  the  manu- 
facture of  flint  glass.  United  with  fatty  acids  it  forms  insoluble  soaps  (the 
well-known  diachylon,  or  lead  plaster);  and  boiled  with  linseed-oil,  it  consti- 
tutes a  varnish  much  used  by  cabinet-makers. 

Red-Lead,  or  Minium,  2  P  b  0 ,  P  b  02,  is  a  compound  of  prot- 
oxyd~and  peroxyd  of  lead.  It  is  formed  by  exposing  protoxyd  of  lead,  for  a 
long  tims,  to  the  action  of  air,  at  a  temperature  below  fusing.  It  possesses  a 
brilliant  red  color,  and  is  much  used  in  the  arts  in  the  manufacture  of  glass, 
as  a  pigment,  and  for  the  coloring  of  red  sealing  wax  and  of  paper. 

599.  Carbonate    of    Lead,    P  b  0 ,  C  Os.  —  White-Lead  —  This  salt 
occurs  in  nature,  but  is  prepared  artificially,  in  immense  quantities,  for  use  as 
a  paint     Pure  carbonate  of  lead  is  a  soft,  white  powder,  insoluble  in  water, 
but  easily  dissolved  by  dilute  nitric  or  acetic  acids. 

Two  methods  are  in  use  for  making  white  lead.  One  of  these  consists  in 
dissolving  litharge  in  acetic  acid,  and  precipitating  the  lead  as  carbonate,  by  a 
current  of  carbonic  acid  gas.  The  best  white  lead  is,  however,  made  by  a  pro- 
197.  cess  known  as  the  "  Dutch  method."  A  great  number  of 
small  earthen  pots  are  partially  filled  with  weak  vinegar, 
and  a  thin  sheet  of  lead,  coiled  in  a  spiral,  placed  in 
each.  (See  Fig.  197.)  The  pots  are  then  each  covered 
with  a  plate  of  lead,  and  arranged  in  rows  and  tiers,  one 
above  the  other,  to  the  height  of  15  or  20  feet,  and  the 
whole  finally  covered  with  decomposing  stable  manure  or 
spent  tan.  After  the  lapse  of  several  months,  the  rolls 
of  lead  are  found  to  be  mostly  or  entirely  converted 
into  a  pure  white  carbonate,  which  only  requires  washing  aud  grinding  to  fit 
it  for  immediate  use.  The  theory  of  this  curious  process  is  as  follows :  the 


QUESTIONS. — What  oxyds  of  lead  are  there  ?  By  what  names  is  protoxyd  of  lead 
known  ?  How  is  it  prepared  ?  What  are  its  properties  and  uses  ?  What  is  red-lead  ? 
What  other  name  is  applied  to  it  ?  What  are  its  uses  ?  What  is  white-lead  ?  How  is  it 
prepared  ? 


LEAD, — TIN.  375 

heat  of  tho  decomposing  dung,  etc.,  volatilizes  a  portion  of  the  vinegar,  as 
noetic  acid)  and  under  the  influence  of  air  and  acid  fumes,  a  crust  of  acetate 
of  lead  is  formed  upon  the  surface  of  the  metal.  The  carbonic  acid,  generated 
from  the  slow  decay  and  decomposition  of  the  materials  of  the  hot-bed,  readily 
converts  this  salt  into  carbonate  of  lead,  leaving  the  acetic  acid  free  to  com- 
'  bine  with  an  additional  portion  of  lead,  which  is,  in  turn,  again  decomposed ; 
and  this  action  is  repeated  until  the  whole  of  the  lead  is  converted  into  a  car- 
bonate. White  lead  is  largely  adulterated  with  sulphate  of  baryta,  but  llio 
fraud  may  be  easily  detected  by  digesting  a  sample  in  nitric  or  acetic  acids, 
when  tho  baryta  will  remain  undissolved. 

600.  The  most  ready  solvent  for  lead  is  nitric  acid ;  dilute  sulphuric  and 
hydrochloric  acids  not  acting  upon  it  to  any  great  extent. 

Tho  presence  of  lead  in  solution  may  be  easily  detected  by  any  of  the  fol- 
lowing tests:  with  sulphuric  acid  it  forms  a  white,  insoluble  precipitate — sul- 
phate of  lead;  with  sulphuretted  hydrogen,  a 
black  sulphide,  visible,  when  the  quantity  of  lead 
present  is  very  minute,  only  after  a  little  time ; 
and  with  solutions  of  bi-chromate  of  potash  or 
iodide  of  potassium,  yellow  precipitates. 

Zinc  precipitates  lead  from  its  solution  by  vol- 
taic action,  in  the  form  of  crystalline  metallic 
particles,  forming  what  is  known  as  the  lead- 
tree.  (Fig.  198.  §  255.) 

In  case  of  poisoning  by  a  dose  of  soluble  lead 
salts,  the  best  antidote  'is  Epsom  salts  (sulphate 
of  magnesia),  with  which  tho  lead  forms  an  in- 
soluble and  inert  sulphate.  This  remedy,  how- 
ever, is  ineffectual  in  the  more  usual  forms  of  lead-poisoning,  in  which  the 
metal  is  introduced  into  the  system  in  minute  quantities,  in  water  or  in  articles 
of  diet 

601.  Alloys   of   Load. — Tho  alloys  of  lead  are  numerous  and  impor- 
tant.    Shot  is  an  alloy  of  lead,  with  a  small  proportion  of  arsenic,  which 
hardens  it,  and  facilitates  its  separation  into  globules.     In  the  manufacture 
of  shot,  the  lead  is  melted  at  the  top  of  high  towers  built  for  the  purpose, 
and  poured  into  a  vessel  perforated  in  the  bottom  with  numerous  small  holes. 
The  lead,  in  running  through,  is  separated  into  drops,  which  falling  through 
the  height  of  the  tower,  become  spherical,  and  cool  before  reaching  a  reser- 
voir of  water  placed  for  their  reception  at  tho  base  of  the  tower.     For  the 
manufacture  of  the   largest  sized  shot,  a  tower  of  at  least  150  feet  high  is 
required.     Shot  are  proved,  and  the  different  sizes  separated,  by  rolling  them 
down  an  inclined  board.     Those  which  are  irregular  in  shape,  roll  off  at  the 
sides,  or  stop,  while  the  perfectly  spherical  ones  continue  in  a  straight  course. 


QUESTION'S.— -What  is  the  most  ready  solvent  of  lead  ?  How  may  the  presence  of  lead 
in  solution  be  detected  ?  What  are  antidotes  to  lead-poisoning  ?  How  are  shot  manufac- 
tured ?  What  is  their  composition  ?  Ho*  are  shot  proved  ? 


876  INORGANIC    CHEMISTRY. 

Type-metal  is  an  alloy  of  3  parts  lead  and  1  of  antimony.  This  alloy  is  suffi- 
ciently fusible  to  allow  of  its  being  readily  cast,  and  it  expands  at  the  mo- 
ment of  solidification,  and  copies  the  mold  accurately.  Solder  is  an  alloy  of 
lead  and  tin. 

602.  Tin,— Equivalent,   59;    Symbol,    Sn  (Stannum)  ; 
Specific  gravity,  7'29. — Tin  occurs  in  nature  usually  as  an 
oxyd,  but  sometimes  as  a  sulphide. 

Its  ores  are  very  sparingly  distributed  over  the  earth — the  most  important 
tin-mines  being  those  of  Corn-wall,  England,  and  Malacca,  in  Southern  Asia. 
It  is  also  mined  to  a  limited  extent  in  Germany,  and  in  a  few  localities  in 
Mexico  and  South  America.  It  has  hitherto  only  been  discovered  in  one 
locality  in  the  United  States,  at  Jackson,  N.  H.,  in  very  email  quantities. 

Tin  of  two  qualities,  as  regards  purity,  is  recognized  in  commerce,  viz., 
"  block"  or  "  bar"  tin,  and  "  grain"  tin ;  the  latter  being  a  refined  metal. 

603.  Properties  , — The  properties  which  characterize  tin  and  render 
it  valuable  in  the  arts,  are  its  malleability,  fusibility,  softness,  silver-like  color 
and  luster,  and  especially  its  slight  affinity  for  oxygen,  which  enables  it  to 
retain  its  brilliancy  at  ordinary  temperatures,  in  the  presence  of  air  and  moist- 
ure.    Tin  melts  at  442°  F.     If  heated  above  this  point  It  is  not  sensibly 
volatilized,  but  becomes  rapidly  oxydized,  and  burns  with  a  brilliant  white 
light.     When  a  bar  of  metallic  tin  is  bent  backward  and  forward,  it  has  a 
peculiar  creaking  or  crackling  sound,  which  is  termed  the  "  tin  cry ;"  this 
is  due  to  the  crystalline  texture  cf  the  tin,  the  crystals  moving  upon  each 
other.     Tin  is  almost  insoluble  in  dilute  sulphuric  acid,  and  dissolves  slowly 
in  hydrochloric  acid.     Nitric  acid  acts  upon  it  with  great  violence,  not  dis- 
solving the  metal,  but  converting  it  into  a  white  powder,  the  binoxyd  of  tin. 
This  reaction  may  be  easily  illustrated  by  pouring  dilute  nitric  acid  upon  a 
little  tin-foil  in  a  porcelain  dish.     The  binoxyd  of  tin  thus  formed,  when  ren- 
dered anhydrous  by  ignition,  constitutes  the  putty  powder  used  for  polishing 
glass,  and  for  the  manufacture  of  enamels. 

604.  "With  oxygen  tin  unites  to  form  several  oxyds,  the  principal  of  which 
are  the  protoxyd,  SnO,  and  the  peroxyd  or  binoxyd,  SnOa.     This  last  oxyd 
in  its  hydrated  condition,  has  the  character  of  an  acid,  and  is  then  known 
as  stannic  acid,  Sn0.i,HO.     Tin  also  unites  with  chlorine  to  form  two  chlor- 
ides, the  protochloride,  SnCI,   and  the  perchloride,  SnClj.     The  last-named 
chloride  is  an  old  and  very  curious  compound,  "which  was  formerly  called  the 
"fuming  liquor  ofLibavius"     It  is  a  dense,  fuming  liquid,  prepared  by  ex- 
posing melted  tin  to  the  action  of  dry  chlorine.     A  preparation  of  bi-chlorido 
of  tin  is  extensively  used  in  dyeing  as  a  mordant.     A  bi-sulphuret  of  tin,  SnS2, 
formed  by  exposing  to  a  low  red  heat  in  a  glass  flask  a  mixture  of  12  parts 

QTTESTIONB.— What  is  type-metal?  What  Is  solder?  What  is  said  of  the  occurrence 
and  distribution  of  tin  ?  What  two  qualities  of  tin  are  known  in  commerce  ?  What  arc 
the  characteristic  properties  of  tin  ?  What  is  "  tin-cry  ?"  What  is  the  action  of  acids 
upon  tin  ?  What  is  putty  powder  ?  What  are  the  principal  oxyds  of  tin  ?  What  is  said 
of  the  chlorides  of  tin  ?  What  is  the  composition  of  bronze  powders  ? 


COPPER. — BISMUTH.  377 

tin,  6  mercury,  6  sal-ammoniac,  and  t  flowers  of  sulphur,  is  of  a  brilliant 
gold  color,  and  is  known  as  mosaic  gold.  It  constitutes  the  well-known 
bronze  powders  used  in  printing'  and  in  the  manufacture  of  paper-hangings. 

605.  The  useful  applications  of  metallic  tin  are  very  numerous.     Tin-plate, 
of  which  ordinary  articles  of  tin-ware  are  made,  is  sheet-iron  superficially 
coated  with  tin.     It  is  prepared  by  first  rendering  the  surface  of  the  iron 
chemically  clean  by  the  action  of  acids,  and  then  immersing  the  sheet-metal 
for  a  considerable  length  of  time  in  a  bath  of  molten  tin  ;  the  union  of  the  two 
metals,  thus  effected,  is  not  a  case  of  simple  adhesion,  but  the  tin  forms  with 
the  iron  an  alloy.     Britannia-metal,  which  is  much  used  for  the  manufacture  of 
tea-pots  and  cheap  spoons,  consists  of  equal  parts  of  tin,  brass,  antimony,  and 
bismuth.     Pewter  of  the  best  quality,  consists  of  4  parts  tin  and  1  of  lead. 
Ordinary  brass  pins  are  tinned,  or  whitened,  by  boiling  them  in  a  vessel  con- 
taining tin  in  a  finely-divided  state,  and  a  solution  of  cream  of  tartar  in  water. 
The  acid  of  the  cream  of  tartar  effects  a  solution  of  some  of  the  tin  in  the 
first  instance,  which  on  longer  boiling  separates  as  a  metal  upon  the  more 
electro-positive  brass. 

SECTION    YI. 

COPPER     AND    BISMUTH. 

606.  Copper . — Equivalent,  31'7  ;  Symbol,  Cu  (Cuprum) ;  Specific  gravity, 
8 '9. — Copper  is  frequently  found  native,  generally  in  small  crystals,  but  some- 
times in  immense  masses,  as  in  the  mines  on  Lake  Superior.     Its  ores,  also, 
are  numerous  and  abundant — the  most  important  being  the  sulphurets  of 
copper,  and  the  red  oxyd.     Carbonate  of  copper,  constituting  the  beautiful 
green  mineral  malachite,  is  also  found  in  sufficient  abundance  in  some  locali- 
ties to  admit  of  working — especially  in  Siberia,  Eastern  Africa,  etc. 

607.  Properties . — Copper  is  one  of  the  metals  which  has  been  longest 
known  to  man,  and  was  extensively  used  long  before  the  working  of  iron 
was  understood.     It  is  moderately  hard,  tenacious,  ductile,  and  malleable, 
and  is  the  only  metal,  with  the  exception  of  titanium,  which  has  a  red  color. 
Copper  requires  a  high  degree  of  temperature  for  fusion  (1990°  F.),  and  when 
exposed  to  an  intense  heat  is  somewhat  volatile — its  vapor  burning  with  a 
green  flame.     It  is  one  of  the  best  conductors  of  heat  and  electricity. 

At  ordinary  temperatures,  in  a  dry  atmosphere,  copper  remains  unchanged, 
but, when  exposed  to  a  moist  air  it  quickly  tarnishes,  and  ultimately  becomes 
covered  with  a  strongly-adherent  green  crust,  consisting  chiefly  of  carbonate. 
Pure  water  has  little  or  no  action  upon  copper,  but  in  sea-water,  or  solutions 
of  the  chlorides,  it  is  gradually  corroded.  The  corrosion  and  waste  of  the 
copper  sheathing  of  ships  is  due  chiefly  to  the  oxygen  contained  in  sea-water, 

QITESTIONB.— What  is  tin-plate  ?  "What  is  Britannia-metal  ?  What  is  pewter  ?  How- 
are  pins  whitened?  What  is  said  of  the  occurrence  of  copper  in  nature?  What  are  its 
chief  properties?  What  is  the  durability  of  copper  in  various  situations  ?  What  occa- 
sions the  corrosion  of  copper  sheathing  ? 


378  INORGANIC     CHEMISTRY. 

and  to  the  friction  of  the  water;  the  corrosion  being  greatest  at  those  points 
where  the  bubbles  of  air  inclosed  in  the  water,  by  the  surging  at  the  bow, 
rise  to  the  surface  and  break  against  the  bottom  of  the  vessel  Corrosion  of 
a  ship's  sheathing  is  also  slow  in  mid-ocean  compared  to  what  it  is  at  the 
mouths  of  tropical  rivers,  or  in  harbors,  where  the  water  is  filled  with  par- 
ticles of  organic  matter  in  a  state  of  decomposition. 

60S.  The  most  ready  solvent  of  copper  is  nitric  acid.  (§  344  )  Many  of 
the  weak  vegetable  acids  also  attack  metallic  copper,  but  dilute  sulphuric  and 
hydrochloric  acids  have  scarcely  any  action  upon  it. 

609.  The  two  principal  oxyds  of  copper  are  the  protoxyd,  or  black  oxyd, 
CuO,  and  the  suboxyd,  or  red  oxyd,  Cu2O. 

610.  Protoxyd    of   Copper  is  the  basis  of  all  the  ordinary  salts  of 
copper.     It  is  prepared  by  heating  metallic  copper  to  redness  in  a  current  of 
air,  and  then  suddenly  quenching  it  in  cold  water ;  or  more  conveniently  by 
decomposing  the  nitrate  of  copper  by  heating  it  to  redness — the  product  in 
the  first  instance  being  black  scales,  and  in  the  last  a  dense  black  powder. 
It  may  also  be  obtained  as  a  hydrate  of  light  blue  color  by  the  addition  of 
caustic  potash  to  a  solution  of  any  of  its  salts,  (as  blue  vitriol).     Protoxyd  of 
copper  is  a  compound  of  considerable  importance  in  chemistry  and  the  arts ; 
when  mixed  with  organic  substances,  and  heated,  it  gives  up  all  its  oxygen, 

and  is  hence  much  used  to  effect  the 
complete  combustion  of  these  bodies  in 
a  process  by  which  their  elementary 
composition  is  determined;  it  is  also 
used  for  imparting  to  glass  and  porcelain 
a  beautiful  green  color. 

Suboxyd  of  copper  is  found  native, 
and  may  be  prepared  by  heating  a  mix- 
ture of  5  parts  of  black  oxyd  and  4  parts 
of  fine  copper  filings  in  a  covered  crucible ;  the  red  coating  which  is  formed 
when  metallic  copper  (as  a  cent,  for  example,  see  Fig.  199)  is  slightly  heated 
and  suddenly  cooled,  is  also  suboxyd  of  copper.  Its  principal  industrial 
value  is  for  imparting  to  glass  a  beautiful  ruby  or  purple  color. 

611.  Sulphate    of  Copper,  Blue  vitriol,  CuO,SOs,  is  one  of  the  most 
important  of  the  salts  of  copper,  and  is  formed  by  heating  metallic  copper 
with  concentrated  sulphuric  acid.     It  crystallizes  in  beautiful  blue  crystals, 
and  is  soluble  in  4  parts  of  cold  and  2  of  boiling  water.     Large  quantities  of 
this  salt  are  used  in  calico-printing,  in  the  preparation  of  most  of  the  other 
salts  of  copper,  and  as  an  agent  for  exciting  galvanic  batteries.     Wood  steeped 
in  a  solution  of  sulphate  of  copper  is  protected  against  dry-rot,  and  a  wash 
of  it  on  the  wood- work  of  cellars  is  highly  serviceable  hi  preventing  the 
formation  of  mold.     Animal  substances  thoroughly  imbued  with  it  and  then 
dried,  remain  unaltered. 

QUESTIONB. — What  is  the  most  ready  solvent  of  copper  ?  What  are  the  two  principal 
oxyds  of  copper  ?  What  is  said  of  protoxyd  of  copper  ?  What  of  suboxyd  of  copper  ? 
What  is  the  composition  of  blue  vitriol  ?  What  are  its  uses  and  properties  ? 


C  0  P  P  E  E  . — B  I  S  M  U  T  H  .  379 

612.  Nitrate    of   Copper,    CuO,    No5,  is  a  beautiful  blue,  efflor- 
escent salt,  formed  by  dissolving  metallic  copper  in  nitric  acid.     It  is  highly 
corrosive,  and  easily  decomposed.     Its  tendency  to  decomposition  may  be  il- 
lustrated by  closely  enveloping  a  few  moist  crystals  of  nitrate  of  copper  in 
tin-foil,  and  placing  the  parcel  upon  a  porcelain  dish ;  the  affinity  of  the  tin 
for  the  nitric  acid  in  a  short  time  occasions  intense  chemical  action,  accom- 
panied by  the  phenomenon  of  ignition  ;  a  paper  also,  moistened  with  a  strong 
solution  of  this  salt,  cannot  be  rapidly  dried  without  taking  fire  from  the  de- 
composition of  the  nitric  acid. 

613.  Verdigris . — Sub- Acetate  of  Copper. — Yerdigris  is  a  salt  of  acetic 
acid  (the  acid  of  vinegar)  and  oxyd  of  copper.     It  may  be  formed  experi- 
mentally by  moistening  from  time  to  time  a  copper  coin  with  vinegar,  which 
occasions  the  production  of  a  green  coating.     It  is  prepared  on  a  large  scale, 
either  directly  from  copper  and  vinegar  (green  verdigris),  or  indirectly  by 
spreading  the  refuse  of  pressed  grapes  upon  plates  of  copper  exposed  to 
the  air ;  in  this  latter  case  the  juice  adhering  to  the  mash  gradually  changes 
to  vinegar,  and  forms  blue,  or  French  verdigris.     This  salt  is  much  used  in 
the  arts  as  a  pigment. 

614.  Characteristics   of  the   Salts   of  Copper . — Most  of 
the  salts  of  copper  have  a  blue  or  green  color,  and  nearly  all  are  soluble  in 
water.   'They  are  distinguished  by  a  nauseating  metallic  taste,  and  when 
taken  internally  act  as  deadly  poisons,  producing  violent  vomiting,  followed 
by  exhaustion  and  death.     Black  oxyd  of  copper  is  soluble  in  oils  and  fats, 
so  that  greasy  matters  boiled  in  an  copper  saucepan  which  is  not  kept  bright, 
are  liable  to  become  impregnated  with  the  metal ;  verdigris  may  also  be  in- 
troduced into  food  from  the  cooking  of  acid  vegetables  or  fruits  in  copper 
vessels  ;  the  use  of  copper  in  domestic  economy  ought,  therefore,  to  be  dis- 
pensed with  as  far  as  practicable.     The  best  antidote  against  copper  poison- 
ing is  raw  white  of  eggs,  the  albumen  of  which,  by  forming  an  insoluble 
compound  with  the  metal,  renders  it  inert.     Milk,  or  sugar  mixed  with  iron 
filings  are  also  efficacious. 

615.  Alloys    of    Copper  , — The  alloys  of  copper  are  extensively  used 
in  the  arts.     Brass  is  an  alloy  of  copper  and  zinc ;  the  usual  proportions 
being  66  parts  of  copper  and  34  zinc.     By  varying  the  proportions,  however, 
the  varieties  of  brass  known  as  "red  metal,"  "pinchbeck,"  "  Muntz,"  or 
sheathing  metal,  etc.,  may  be  obtained.     Gun-metal,  used  in  the  fabrication 
of  brass  ordnance,  is  an  alloy  of  90  parts  of  copper  and  10  of  tin.     Bell-metal 
and  specidum-metal  contain  a  larger  proportion  of  tin.     Bronze  for  statuary 
consist  of  91  parts  copper,  2  of  tin,  6  of  zinc,  and  1  of  lead.     The  brass  of 
the  ancients  was  an  alloy  of  copp'er  and  tin. 


QUESTIONS. — What  is  said  of  nitrate  of  copper  ?  What  is  verdigris  ?  How  is  it  pre- 
pared ?  What  are  the  characteristics  of  the  salts  of  copper  ?  Why  is  the  use  of  copper 
vessels  in  culinary  operations  unadvisable  ?  What  is  the  best  antidote  against  copper 
poisoning  ?  What  is  brass  ?  What  is  gun-metal— bell -metal— bronze  ? 


380  INORGANIC    CHEMISTRY. 

616.  Bismuth  is  a  reddish- white,  hard,  brittle  metal, 
which  is  generally  found  native  in  small  quantities. 

It  crystallizes  from  fusion  in  cubic  crystals  of  great  brilliancy.  Its  principal 
employment  is  in  the  preparation  of  alloys,  a  slight  admixture  of  it  increasing 
the  fusibility  of  several  metals  to  a  remarkable  extent.  Oxyd  of  bismuth  is 
used  to  some  extent  in  medicine,  and  also  as  a  cosmetic  (pearl  powder). 

SECTION    Y 1 1 . 

URANIUM,    VANADIUM,    TUNGSTEN,    COLUMBIUM,    TITANIUM,    MOLYBDENUM, 
NIOBIUM,    PELOPIUM,    ILMENIUM,    ETC. 

617.  All  these  metals  are  very  sparingly  distributed  over  the  surface  of  the 
earth,  and  some  of  them  are  so  rare,  that  they  have  been  seen  by  only  a  few 
chemists.  Uranium  and  titanium  are  used  to  some  extent  for  the  coloration 
of  porcelain  and  enamels ;  and  molybdenum,  in  combination,  as  molybdate  of 
ammonia,  constitutes  the  most  delicate  known  test  of  the  presence  of  phos- 
phoric acid  in  solution. 

SECTION    YIII.   • 

ANTIMONY    AND     ARSENIC. 

618.  Antimony, — Equivalent,  12'9;  Symbol,  Sb.  (Stib- 
ium).— Antimony  is  a  blueish-white  metal,  with  a  highly 
crystalline  texture,  so  brittle  that  it  may  be  easily  reduced 
in  a  mortar  to  a  fine  powder.* 

"When  exposed  to  air  and  moisture,  at  ordinary  temperatures,  it  under- 
goes no  change;  but  if  heated,  it  burns  brilliantly,  emitting  copious  white 
fumes,  which  consist  chiefly  of  a  teroxyd  of  antimony.  A  very  interesting 
experiment  consists  in  fusing  a  little  of  the  metal  on  charcoal  before  the  blow- 
pipe, and  projecting  the  melted  globule  upon  the  floor  or  an  inclined  board ; 
the  moment  it  strikes  the  hard  surface,  it  bursts  into  a  multitude  of  little 
spheroids,  which  radiate  in  all  directions,  leaving  a  trail  of  white  smoke  (oxyd) 
behind  them.  Antimony  is  not  used  by  itself  in  the  arts,  but  it  enters  into 
the  composition  of  several  important  alloys,  as  type  metal,  Britannia  metal^ 
etc.  Finely-powdered  antimony,  sprinkled  into  a  jar  of  chlorine  gas,  ignites, 
and  occasions  a  miniature  shower  of  fire. 


*  Antimony  was  first  made  known  by  Basil  Valentine,  an  alchemist  and  monk,  of  Er- 
furth,  Germany.  The  etymology  of  its  name  is  'said  to  be  due  to  the  following  circum- 
stance :  its  discoverer  having  observed  that  its  effects,  when  administered  to  hogs,  were 
beneficial,  tried  it  upon  his  fellow-monks.  The  result  of  the  experiment,  however,  was 
that  the  monks  sickened  and  died— hence  the  name  antimoine,  anti-monk,  antimony. 

QITESTIONS. — What  is  said  of  bismuth  ?  What  are  its  uses  ?  What  is  said  of  uranium, 
titanium,  and  molybdenum  ?  What  of  antimony?  What  are  the  properties  of  antimony! 
What  its  industrial  uses  ? 


ANTIMONY. — ARSENIC.  381 

619,  Antimony  forms  three  oxyds,  the  most  important  of  which  are,  the 
teroxyd  of  antimony,  Sb03,  and  antimonic  acid,  SbOg. 

620.  The  compounds  of  antimony  are  remarkable  for  their  medicinal  ef- 
fects, and  are  classed  in  pharmacy  among  the  important  remedial  agents. 
'When  taken,  however,,  in  inordinate  doses,   they  act  as  poisons.      Tartar 
emetic  is  a  double  salt  of  tartarate  of  potash  and  tartarate  of  antimony.     It  is 
formed  by  boiling  oxyd  of  antimony  with  cream  of  tartar,  which  last  is  a  salt 
of  potassa  and  tartaric  acid,  containing  free  acid;  this  free  acid  combines 
with  the  oxyd  of  antimony,  and  thus  forms  a  double  salt.     Tartar  emetic,  dis- 
solved in  sherry  wine,  in  the  proportion  of  two  grams  of  the  former  to  a  fluid 
ounce  of  the  latter,  forms  the  well-known  "wine  of  antimony." 

Sulphuretted  hydrogen,  added  to  solutions  of  antimony  (as  a  solution  of  tar- 
tar emetic  in  water),  precipitates  the  metal  in  the  form  of  a  peculiar  and  highly 
characteristic,  orange-colored  sulphuret. 

621,  Arsenic,— Equivalent,  75;  Symbol,  As. — Arsenic 
Is  sometimes   found   native,  but  generally  occurs  in  the 
form  of  an  alloy  with  some  other  metal,  especially  with 
iron,  cobalt,  nickel,  copper,  or  tin. 

The  greater  part  of  the  arsenic  of  commerce  is  obtained  in  Silesia,  in  Ger- 
many, by  roasting,  in  furnaces,  a  double  sulphuret  of  iron  and  arsenic, — called 
mispickel,  or  the  arsenides  of  nickel  and  cobalt.  The  arsenic,  volatilized  by 
heat  in  the  form  of  an  oxyd — arsenious  acid — is  condensed  and  collected  ia 
the  form  of  a  white  powder  in  large  chambers,  into  which  the  flues  from  the 
furnace  open.* 

Metallic  arsenic  may  be  obtained  by  heating  arsenious  acid  with  powdered 
charcoal  in  a  tightly-closed  crucible.  It  is  a  dark,  steel-gray  colored  metal, 
extremely  brittle,  and  may  be  easily  reduced  to  powder.  It  is  sold  by  drug- 
gists under  the  very  objectionable  names  of  fly-powder,  fly-poison,  cobalt,  etc. 
When  heated,  it  volatilizes  without  fusion ;  and  if  air  be  present,  it  oxydizes 
to  arsenious  acid.  Its  vapor  has  a  remarkable  odor  of  garlic,  which  is  so  pe- 
culiar and  noticeable,  that  it  is  regarded  as  one  of  the  characteristic  tests  of 
the  presence  of  this  element ;  this  odor  is  easily  recognized  by  heating  a  frag- 
ment of  arsenic,  or  arsenious  acid  on  charcoal  before  the  blow-pipe. 

622.  Tho  oxyds  of  arsenic  are  two; — Arsenious  acid,  AsOs,  and  arsenic 
acid,  AsOs. 


*  The  opening  of  these  chambers,  and  the  removal  of  arsenic,  is  a  task  of  great  danger, 
tmd  is  performed  about  once  in  six  weeks.  The  workmen  engaged  in  the  operation,  as 
protection  against  the  poison,  are  completely  encased  in  leather,  with  glazed  apertures  for 
the  eyes.  They  also  wear,  in  addition,  damp  cloths  over  their  mouths  and  nostrils,  in 
order  to  prevent  the  inhalation  of  minutely-divided  particles. 

QUESTIONS.— What  are  the  chief  oxyds  of  antimony?  What  is  tartar-emetic?  What 
is  wine  of  antimony?  What  is  a  characteristic  test  of  antimony  in  solution?  In  what 
form  does  arsenic  occur  naturally  ?  How  is  the  arsenic  of  commerce  prepared  ?  What  is 
said  of  metallic  arsenic  ?  What  of  its  oxyds  ? 


382  INORGANIC     CHEMISTRY. 

Arsenious  Acid,  As 02. —  White  Arsenic,  RaVs-bane. — This  oxyd  is 
the  substance  to  which  the  name  arsenic  is  popularly  applied,  and  is  the  well- 
known  poison.  It  occurs  in  commerce  as  a  white  powder,  but  when-  freshly 
sublimed  it  assumes  the  appearance  of  a  semi-transparent  solid,  which  gradu- 
ally becomes  opaque  and  white,  like  porcelain.  It  is  soluble  in  about  11  parts 
of  boiling  water,  but  to  a  very  much  less  extent  in  cold  water.  Its  solution 
is  colorless,  and  almost  tasteless,  which  circumstances  greatly  facilitate  its  em- 
ployment for  criminal  purposes.  It  dissolves  freely  in  hot  hydrochloric  acid, 
and  in  solutions  of  the  alkalies. 

Arsenious  acid  combines  with  bases  to  form  arsenites :  arsenite  of  potash  is 
used  in  medicine  under  the  name  of  Fowler's  solution ;  and  arsenite  of  copper 
constitutes  the  delicate  and  beautiful  green  pigment  known  in  commerce  as 
Sclieelds  green.  Its  poisonous  properties  have  also  been  taken  advantage  of 
for  the  destruction  of  vermin.  To  destroy  rats  and  mice,  the  poison  should 
be  mixed  with  flour  or  lard,  but  not  in  too  large  a  quantity,  or  these  animals 
will  not  touch  it.*  Arsenious  acid,  when  placed  in  contact  with  organic  sub- 
stances, prevents  their  decay,  and  may  be  hence  used  with  advantage  for  the 
preservation  of  stuffed  and  dried  objects  of  natural  history. \ 

623.  Arsenic   Acid,    As  Os,  is  formed  by  treating  arsenious  acid  with 
nitric  acid,  and  evaporating  the  solution  to  dryness.     It  unites  with  metallic 
oxyds  to  form  arseniates:  the  arseniate  of  potash  being  used  to  a  very  great 
extent  in  calico  printing,  not  so  much  to  produce  colors  as  to  prevent  their 
adherence  to  certain  portions  of  the  fabric. 

Arsenic  combines  with  hydrogen  to  form  a  volatile  and  highly  poisonous 
gas — arseniuretted  hydrogen.  There  are  also  several  compounds  of  arsenic 
and  sulphur,  which  are  used  as  pigments  and  in  pyrotechny :  realgar,  AsSs, 
is  a  beautiful  red  pigment,  and  is  a  principal  constituent  of  the  so-called  white 
Indian  fire,  often  used  as  a  signal-light ;  orpirment,  AsSs,  is  a  golden  yellow 
pigment ; — both  of  these  substances  are  found  native. 

624.  Arsenic  forms  alloys  with  most  of  the  metals,  which  are  generally  brit- 
tle and  easily  fusible.     Its  presence  in  iron  is  highly  injurious. 

*  If  the  poison  is  put  in  stables,  the  receptacles  of  meal  and  fodder  should  be  carefully 
covered  over,  that  the  poisoned  rats  may  not  vomit  the  poison  into  them. 

t  It  is  best  used  for  this  purpose  in  the  form  of  an  arsenical  soap,  which  may  be  pre- 
pared by  mixing  100  parts  of  white  soap,  100  of  arsenious  acid,  36  carbonate  of  potash,  15 
camphor,  and  12  quicklime.  The  soap  is  to  be  scraped  and  melted  with  a  little  water  at 
a  gentle  heat;  then  add  the  potassa  and  the  lime,  and  mix  them  well  together—the  arsen- 
ious acid  is  afterward  added  gradually,  and  well  incorporated.  The  camphor  is  reduced 
to  powder  by  rubbing  it  in  a  mortar,  with  the  addition  of  a  few  drops  of  strong  alcohol, 
and  when  the  soap  is  cold  this  is  well  mixed  in.  A  portion  of  the  soap  dissolved  in  water 
is  applied  to  the  preparations  by  means  of  a  camel's  hair  pencil.  It  constantly  exhales 
the  odor  of  arseniuretted  hydrogen,  and  effectually  destroys  insects  and  their  eggs. — 
DUMAS. 

QUESTIONS.— What  is  said  of  the  arsenic  of  the  shops  ?  What  are  the  properties  of  ar- 
Bcnious  acid?  What  are  its  salts  termed?  What  is  Fowler's  solution  ?  What  is 
Scheele'  green  ?  What  are  the  uses  of  arsenic  ?  What  is  arsenic  acid  ?  What  are  its 
salts  called  ?  What  are  its  uses  ?  What  is  said  of  the  other  compounds  of  arsenic  ? 


ARSENIC.  383 

625.  Characteristics  and  Tests    for  Arsenic.  —  The   com- 
pounds of  this  metal  are  all  highly  poisonous,  either  when  taken  into  the  sto- 
mach, when  applied  to  wounds,  or  when  inhaled  as  vapor.    The  most  effectual 
antidotes,  iu  cases  of  ordinary  poisoning  by  it,  are,  first,  a  powerful  emetic,  and 
tlu-n  the  free  administration  of  the  hydrated  oxyd  of  iron  suspended  in  water 
(§  567) ;  if  this  is  not  at  hand,  calcined  magnesia  may  be  used.     In  the  ab- 
sence of  either  of  these  substances,  the  white  of  eggs,  milk,  sugar,  and  soap- 
suds aro  beneficial,  (this  latter  observation  applying  also  to  almost  all  other 
cases  of  poisoning).      Prompt  action  is,   however,   necessary,  as  arsenic  is 
almost  always  fatal  when  time  is  allowed  for  its  absorption  into  the  system 
in  sufficient  quantity. 

The  frequent  employment  of  arsenic  as  an  agent  in  poisoning,  has  induced 
chemists  to  study  its  nature  and  compounds  so  carefully,  that  its  detection 
when  present  in  the  body,  in  the  materials  which  have  passed  from  the  body, 
in  food  or  in  liquids,  is  a  matter  of  certainty.  Even  though  the  quantity  be 
too  minute  to  be  weighed,  its  existence  in  a  substance  may  be  absolutely  de- 
monstrated and  made  visible  to  the  eye.  Lapse  of  time  can  not  wholly  de- 
stroy this  chemical  evidence  ; — the  body  with  which  the  arsenic  has  become 
incorporated  may  decay,  but  the  poison  remains  unchanged,  and  may  be 
recognized  even  after  the  lapse  of  years.* 

626.  An  investigation  for  the  detection  of  arsenic,  in  cases  where  a  criminal 
prosecution  involving  reputation,  and  perhaps  life,  depends  upon  the  issue, 
should  be  intrusted  only  to  a   professional  chemist,  but  a  description  of  the 
tests  employed,  and  of  the  methods  by  which  evidence  can  be  accumulated, 
are  matters  of  general  interest. 

An  exceedingly  delicate  test  known  as  "  Marsh's  test,"  depends  upon  tho 
property  which  arsenic  possesses  of  forming  a  gas  with  hydrogen,  and  de- 
positing itself,  in  the  metallic  state,  upon  the  surface  of  a  cold  plate  held 
over  the  flame  of  the  burning  gas.  The  experiment  is  made  by  generating 
hydrogen  in  the  usual  manner  from  zinc,  water,  and  sulphuric  acid,  in  a  glass 
flask,  and  allowing  it  to  escape  through  a  perforated  cork  and  tube  of  glass 
drawn  down  to  a  fine  point.  (See  Fig.  200.)  The  hydrogen  evolved  should 
first  be  tested  by  burning  it  against  a  porcelain  plate  to  prove  that  it  is  free 
from  arsenic,  and  then  the  suspected  liquor  is  to  be  introduced  into  the  ap- 
paratus. (For  the  purpose  of  experiment  a  few  drops  of  a  solution  of  arsenious 
acid  in  water,  or  hydrochloric  acid,  may  be  used).  If  arsenic  is  present,  the 
flame  of  hydrogen,  when  brought  in  contact  with  the  surface  of  a  cool  white 


*  In  cases  of  arsenical  poisoning,  putrefaction  of  the  body  after  death  is  retarded  in  a 
remarkable  degree  ;  and  in  many  cases  where  the  body  has  been  disinterred  several  months 
after  death,  it  has  been  found  sufficiently  preserved  from  decay  to  allow  many  of  the 
principal  internal  organs  to  be  distinguished.  In  one  instance,  in  France,  conviction  of 
poisoning  by  arsenic  was  obtained  on  evidence  procured  by  the  celebrated  chemist  Or- 
filla,  from  the  remains  of  a  person  who  had  been  dead  for  a  lengthy  period  of  years. 

QUESTIONS. — What  is  said  of  the  poisonous  effects  of  arsenic?  What  of  its  antidotes  ? 
What  is  said  of  its  detection  in  the  body,  or  in  other  substances?  What  is  Marsh's 
teat? 


384 


INORGANIC     CHEMISTRY. 


FiG.  200. 


plate,  or  saucer,  will  deposit  a  smooth  black  or 
brown  spot  (a  little  metallic  mirror).  One  other 
metal — antimony — will  give  the  same  reaction, 
but  a  drop  of  an  aqueous  solution  of  chloride 
of  lime  instantly  dissolves  the  arsenic  spot,  but 
leaves  the  antimony  unaltered.  If  the  arseni- 
uretted  hydrogen  gas  be  conducted  through  a 
glass  tube  heated  at  one  point  over  a  spirit- 
lamp,  metallic  arsenic  will  be  deposited  in  the 
colder  part  of  it,  forming  a  beautiful  incrus- 
tation. 

Sulphuretted  hydrogen  precipitates  arsenic 
from  its  solutions  in  the  form  of  a  sulphuret  of 
arsenic,  of  a  rich  lemon  color.  This  is  a  very 
accurate  test,  and  so  delicate  that  the  yellow 

tint  is  apparent  when  only  a  ten-thousandth  part  of  arseuious  acid  is  present, 

and  a  precipitate  when  the  proportion  is  as  1  part  of  arsenious  acid  to  80,000 

of  water. 

Reduction  of  the  metal  from  its  oxyds  or  sulphurets  is  a  test  much  relied 

on  in  judicial  investigation.     This  may  be  effected  by  introducing  a  little  ar- 
senious acid,  or  the  sulphuret  obtained  in  the  last  experiment,  mixed  with 

finely-powdered  charcoal  and  carbonate  of  soda,  into  a  glass  tube  of  the 

diameter  of  a  common  quill,  care  being  taken  not  to  soil  the  sides  of  the  tube. 

The  mixture  is  then  gently  heated  by  the 

flame  of  a  spirit-lamp,  when  the  metallic 

arsenic  sublimes,  and  is  condensed  as  a 

black,  lustrous  mirror,   c,  in  the  upper 

and  cool  part  of  the  tube.     (See  Fig.  201.) 

A  slip  of  bright  metallic  copper,  placed 

in  a  hot  solution  of  arsenious,  or  arsenic 

acid,  acidulated  by  hydrochloric  acid,  is 

soon  coated  by  a  gray  film  of  metallic 

arsenic.      This  is  known   as   Reinsch's 

test,  and  is  affirmed  to  show  the  presence 

of  a  250,000th  part  of  arsenic  in  solution.     It  is  a  test  readily  applicable  even 

when  the  solution  is  contaminated  by  the  presence  of  so  much  organic  matter 

as  to  impair  the  accuracy  of  other  reactions. 

A  dose  of'  from   2  to  3  grains  of  arsenic  is  generally  regarded  as  fatal, 

though  larger  doses  are  sometimes  rejected  from  the  stomach  by  vomiting. 

A  dose  of  from  l-15th  to  l-30th  of  a  grain  is  said  to  warm  and  exhilarate 

the  system,  and  increase  its  vigor,  and  the  peasants  of  Hungary  are  reported 

to  be  in  the  habit  of  using  it  for  this  purpose. 

QUFSTIONS. — What  other  metal  gives  the  same  reaction?  How  may  antimony  be  dis- 
tinguished from  arsenic  in  this  instance  ?  What  is  the  test  by  sulphuretted  hydrogen  ? 
What  is  the  teat  by  reduction?  What  is  Keiasch's  test?  What  amount  of  arsenic  is 
fatal? 


Fm.  201. 


MERCURY.  385 

627.  Arsenic  and  antimony  are  the  only  metals  which  are  capable  of  com- 
bining with  hydrogen.  In  this  and  several  other  respects,  they  comport  them- 
selves like  metalloids,  and  by  some  chemical  authorities  arsenic  is  regarded 
as  a  non-metallic  element 


CHAPTER    XIV. 

THE     NOBLE    METALS- 

THE  metals  included  in  this  class  are  nine  in  number, 
viz.,  Mercury,  Silver,  Gold,  Platinum,  Palladium,  Rho- 
dium, Ruthenium,  Osmium,  and  Iridium. 

The  principal  characteristic  of  these  metals  is  tfaeir  slight  affinity  for  oxy- 
gen, by  reason  of  whick  their  oxyds  are  easily  decomposed  by  the  action  of 
heat  alone,  the  metal  remaining  in  an  uncombined  state.  The  temperature 
required  to  effect  this  decomposition  is  less  than  red  heat,  with  the  single 
•exception  of  the  oxyd  of  osmium.  Mercury  and  silver  are  generally  found 
in  nature  as  sulphides ;  the  others  usually  occur  native,  and  are  often  asso- 
ciated with  each  other, 

SECTION   I. 

MERCURY    (Hydrargyrum,  liquid  siker). 
Egvwalent,  100.    Symbol,  Hy.     Specific  gravity,  13-591 

628.  Natural  History  and  Distribution , — Mercury  is  some- 
times found  native,  as  fluid  quicksilver,  but  most  generally  occurs  as  a  sulph- 
ide, forming  a  brilliant  red  mineral  termed  cinnabar.     Its  most  productive 
mines  are  those  of  Almaden  in  Spain,  Idria  in  Austria,  and  New  Almaden 
in  Upper  California.     Considerable  quantities  are  also  obtained  from  locali- 
ties in  Mexico,  Peru,  China,  and  Japan.     It  is  reduced  from  its  ores  by  a  pro- 
cess of  distillation. 

629.  Properties  , — Mercury  is  a  brilliant,  silver- white  metal,  possess- 
ing great  density,  and  also  the  remarkable  property  of  remaining  fluid  at 
common  temperatures.     It  solidifies  (freezes)  at  — 39°  F.,  in  which  state  it 
is  soft  and  malleable.     "When  heated  to  662°  F.  it  boils,  and  yields  an  in- 
visible vapor.     The  metal  also,  at  all  temperatures  above  40°  F.,  undergoes  a 
slight  spontaneous  evaporation — a  fact  easily  proved  by  the  action  exerted 


QUESTIONS.— What  are  distinguishing  characteristics  of  antimony  and  arsenic  ?  What 
are  the  noble  metals  ?  What  are  their  characteristics  ?  Under  what  circumstances  does 
mercury  occur  naturally?  Where  are  its  principal  mines  ?  What  are  its  properties  ?  At 
what  temperature  does  it  solidify  ?  When  boil  ?  What  is  said  of  its  volatility  ? 

17 


INORGANIC    CHEMISTRY. 

upon  a  sensitive  daguerreotype  plate  suspended  a  few  inches  above  a  vessel 
containing  mercury. 

Mercury,  when  pure,  is  not  tarnished  by  exposure  to  air  and  moisture  at 
ordinary  temperatures,  but  when  heated  to  near  its  boiling  point  it  slowly 
absorbs  oxygen,  and  becomes  converted  into  a  crystalline,  dark-red  powder, 
the-  red  oxyd  of  mercury.  This  oxyd,  when  subjected  to  a  dull  red  heatr 
evolves  oxjrgen,  and  is  decomposed  into  its  constituents.  It  was  by  means 
of  this  substance  that  Priestley  first  discovered  the  existence  of  oxygen,  and 
Lavoisier  determined  the  composition  of  atmospheric  air. 

630.  The  most  ready  solvent  of  mercury  is  nitric  acid,  which  dissolves  ic 
with  great  rapidity.     Hydrochloric  acid  has  no  action  upon  it,  and  the  samo 
is  true  also  of  dilute  sulphuric  acid. 

631.  When  pure  mercury  is  agitated  with  ether,  or  oil  of  turpentine,  or 
rubbed  with  sulphur,  sugar,  chalk,  lard,  etc.,  it  is  reduced  to  so  line  a  state 
of  division  that  it  loses  its  metallic  appearance  entirely,  and  becomes  thor- 
oughly incorporated  with  the  foreign  body.     In  its  ordinary  state,  mercury 
is  inactive  as  a  medicine,  but  in  this  state  of  mechanical  division  it  is  readily 
absorbed  by  the  system,  and  becomes  efficacious.     The  well-known  Hue-pill 
is  mercury  rubbed  into  pulverized  chalk  (pulvis  hydrargyri  cum  cretd) ;  and 
mercurial  ointment  is  mercury  incorporated  with  lard. 

632.  Mercury  combines  with  oxygen  in  two  proportions,  forming  a  gray, 
or  suboxyd,  Hy20,  and  the  protoxyd,  or  red  oxyd,  HyO.     This  last  oxyd  is 
a  red  powder,  and  was  called  by  the  old  chemists  red  precipitate, 

633.  Mercury  forms  two  compounds  with  chlorine,  which  correspond  in 
constitution  to  the  t\vo  oxyds,  and  are  of  great  importance  in  medicine  and 
the  arts ;  they  aro  the  subchloride  and  the  chloride. 

634.  Subchloride   of   Mercury,   H  y2C  1 ,  is  the  well-known  medi- 
cine, calomel.     It  may  bo  obtained  by  precipitating  a  solution  of  sub-nitrate 
of  mercury  with  common  salt.     When  pure,  it  is  a  heavy,  white,  insoluble, 
and  tasteless  powder. 

635.  Chloride    of  Mercury,    H  y  C 1 ,  is  known  in  commerce  under 
the  name  of  corrosive  sublimate.    Its  formation  may  be  shown  experimentally 
by  heating  a  globule  of  mercury  in  a  deflagrating  spoon,  and  plunging  it 
into  ajar  of  chlorine  ;  the  metal  takes  fire  and  produces  the  chloride.     Prac- 
tically, it  is  prepared  by  subliming  a  mixture  of  common  salt  and  sulphate 
of  protoxyd  of  mercury. 

Corrosive  sublimate  is  a  dense,  white  crystalline  substance,  soluble  in  16 
parts  of  cold,  and  3  of  boiling  water — its  solution  possessing  a  disgusting 
and  burning  metallic  taste.  It  is  one  of  the  most  deadly  poisons  known  in 
chemistry.  With  albumen  it  unites  to  form  compounds  which  are  nearly 
insoluble;  hence  substances  which  contain  albumen,  such  as  white  of  eggs, 
milk,  etc.,  are  the  most  effectual  antidotes  in  cases  of  poisoning  by  it.  Timber, 

QTTESTIONS. — What  of  its  power  to  resist  oxydation  ?  What  is  its  most  ready  solv- 
ent ?  What  of  its  susceptibility  to  mechanical  division  ?  What  is  blue-pill  ?  What  mer- 
curial ointment  ?  What  are  its  oxyds  ?  What  is  said  of  its  chlorides  ?  What  is  calo- 
mel ?  What  is  corrosive  sublimate  ?  What  aro  its  properties  ?  What  are  antidotes  to  it  ? 


MERCURY.  387 

and  animal  and  vegetable  substances  in  general,  are  effectually  protected 
against  decay  and  the  action  of  insects,  by  steeping  in  a  solution  of  corro- 
sive sublimate.  This  process  is  known  in  the  arts  as  kyanizing,  from  its  in- 
ventor, Mr.  Kyan,  who  first  applied  it  with  great  success  for  the  protection 
of  ship-timber  against  the  effects  of  "  dry  rot."  The  preservative  action  ap- 
pears to  be  due  to  the  circumstance  that  the  corrosive  sublimate  unites 
with  the  organic  substances  to  produce  insoluble  and  poisonous  com- 
pounds. A  solution  of  corrosive  sublimate  in  alcohol  is  much  used  as  a 
preservative  wash  for  plants  in  herbariums,  and  for  other  objects  of  natural 
history. 

636.  Oxyd  of  mercury  forms  several  salts  with  nitric  acid,  the  principal 
of  which  are  the  subnitrate,  HysO,N05,  and  the  nitrate,  HyO,N05.     The  last- 
named  salt  is  used  in  the  arts  as  a  wash  for  rabbit  and  hare  skins,  as  it  im- 
parts to  these  furs  a  property  of  felting  which  does  not  naturally  belong  to 
them. 

637.  S  u  1  EjiJLd  e   of   Mercury,    HyS  ,— This  compound  is  the  most 
abundant  of  the  ores  of  mercury,  and  as  a  mineral  product  is  termed  cinna- 
bar; but  when  prepared  artificially,  it  constitutes  the  beautiful  red  pigment 
known  as  vermilion.     Yermilion  is  prepared  by  subliming  1  part  of  flowers 
of  sulphur  with  6  of  mercury.     The  product  is  a  blackish-red  crystalline 
mass,  which  by  friction  and  pulverization  assumes  a  magnificent  scarlet  color. 

638.  Uses  , — Mercury  is  used  extensively  in  the  arts  in  the  construction 
of  philosophical  instruments  (barometers,  thermometers,  etc.),  in  the  extrac- 
tion of  gold  and  silver  from  their  ores,  in  gilding,  and  in  medicine. 

639.  Alloys    of  Mercury  with  other  metals  are  termed  amalgams. 
An  amalgam  of  4  parts  of  tin  to  1  of  mercury  constitutes  the  material  em- 
ployed for  the  silvering  of  mirrors.     A  strip  of  copper  becomes  amalgamated 
if  rubbed  with  a  solution  containing  mercury.     If  we  make  a  stroke  across 
a  brass  plate  with  a  stick  or  brush  dipped  in  a  solution  of  mercury,  and  af- 
terward bend  the  plate  at  this  place,  it  will  break  as  though  it  had -been 
cut;  the  explanation  of  this  is,  that  the  mercury  of  the  solution  at  once 
penetrates  and  combines  with  the  brass,  and  renders  it  extremely  brittle. 
Mercury,  when  brought  in  contact  with  bars  of  lead,  tin,  and  zinc,  readily 
permeates  them  by  a  species  of  capillary  attraction ;  and  by  employing  a  bar 
of  lead  in  the  form  of  a  syphon,  we  may  gradually  raise  and  draw  off  mer- 
cury from  its  containing  vessel. 

Tin,  lead,  silver,  gold,  and  several  other  metals,  are  dissolved  by  mercury 
to  a  considerable  extent,  without  much  loss  of  fluidity.  It  has,  on  the  con- 
trary, but  little  attraction  for  iron,  and  on  this  account  it  is  generally  pre- 
served in  iron  bottles. 

The  presence  of  mercury,  when  in  solution,  may  be  detected  by  placing  a 

QUESTIONS. — What  is  kyanizing?  How  does  corrosive  sublimate  act  as  a  preserva- 
tive agent?  What  is  said  of  the  nitrates  of  mercury?  "What  is  vermilion?  How  is  it 
prepared  ?  What  are  the  principal  uses  of  mercury  ?  What  are  alloys  of  mercury  termed  ? 
What  forms  the  lustrous  coating  of  mirrors?  How  does  mercury  comport  itself  in  con- 
tact with  the  other  metals  ?  How  may  the  presence  of  mercury  in  solution  be  detected  ? 


38'8  INORGANIC    CHEMISTRY. 

drop  of  the  suspected  liquid  on  a  piece  of  polished  gold,  as  a  half-eagle,  and 
touching  the  metal,  through  the  liquid,  with  a  scrap  of  zinc,  or  with  the  point 
of  a  penknife.  The  part  touched  will  instantly  appear  white,  owing  to  the 
deposition  of  mercury  by  voltaic  action, 


SECTION    II. 

SILVER. 

Equivalent,  108.     Symbol,  Ag.  (Argentum).     Specific  gravity,  10-5. 

640.  Natural    History    and    Distribution.  —  Silver  is  fre- 
quently met  with  in  the  native  state,  but  most  generally  it  is  found  in  com- 
bination with  sulphur,  mixed  with  sulphides  of  lead,  antimony,  copper,  and 
iron.     The  mines  of  Mexico  and  Peru  are  the  most  productive  sources  of  sil- 
ver;  but  it  occurs  in  quantities  sufficient  to  pay  for  working,  in  Norway,  Sax- 
ony, Spain,  and  the  Hartz  mountains. 

641.  Amalgamation  , — Silver  is  obtained  from  ores  free  from  lead,  as 
those  of  South  America  and  Mexico,  by  a  process  termed  Amalgamation, 
which  is  founded  upon  the  ready  solubility  of  silver  and  other  metals  in  met- 
allic mercury.     The  ore  is  first  crushed  to  a  fine  powder,  mixed  with  common 
salt,  and  roasted  at  a  low  red-heat  in  a  furnace.     By  this  treatment  the  silver 
obtains  chlorine  from  the  salt,  and  is  changed  from  a  sulphide  into  a  chloride. 
The  resulting  products  of  the  furnace,  consisting  of  chloride  of  silver,  oxyds 
of  copper,  iron,  and  earthy  matters,  are  then  placed,  with  water  and  a  portion 
of  scrap-iron,  in  barrels  which  revolve  upon  their  axes,  and  the  whole  agitated 
together  for  some  time,  during  which  the  iron  reduces  the  chloride  of  silver  to 
a  state  of  metal,  and  forms  chloride  of  iron ;  a  certain  portion  of  mercury  is  then 
added,  and  the  agitation  continued.     The  mercury  dissolves  out  the  silver,  the 
copper,  and  the  gold,  if  there  be  any,  and  combines  with  them  to  form  an 
amalgam ;  which,  by  reason  of  its  great  weight  and  fluidity,  is  easily  separ- 
ated from  the  other  materials  by  washing  and  subsidence.     This  amalgam  is 
then  pressed  in  woolen  bags,  to  squeeze  out  the  uncombined  mercury,  and  the 
solid  portion  heated  in  a  kind  of  retort,  when  the  last  trace  of  mercury  vol- 
atilizes, and  leaves  the  silver  alloyed  with  copper  or  gold  behind.     In  this 
state  it  is  exported  in  ingots.* 


*  This  process,  as  conducted  in  Mexico  and  South  America  by  the  rude  miners,  is  ex- 
ceedingly imperfect,  and  is  attended  with  an  enormous  loss  of  quicksilver,  by  Volatiliza- 
tion and  the  formation  of  calomel,  HyaCl;  so  much  Bo,  that  it  has  been  calculated  that 
upwards  of  six  million  cwt.  of  mercury  had  been  wasted  in  the  American  mines  up  to  the 
close  of  the  last  century.  It  must  be,  therefore,  apparent,  that  the  great  employment  of 
mercury  is  in  the  mining  of  silver ;  and  previous  to  the  discovery,  a  few  years  since,  of 
the  rich  cinnabar  mines  of  California,  the  price  of  mercury  (owing  to  a  diminished  sup- 
ply from  the  mines  in  Spain  and  Austria)  had  risen  so  high,  that  many  of  the  richest  sil- 
ver-mines of  Mexico  and  Peru  were  of  necessity  abandoned. 

QUESTIONS. — What  is  said  of  the  natural  condition  of  silver  ?    Where  are  its  ; 
mines  ?    How  is  silver  obtained  from  its  ores  by  amalgamation  ? 


SILVER.  .  389 

642.  L  i  q  u  a*  i  0  n  .—Silver  containing  a  large  percentage  of  copper  is  sep- 
arated from  this  metal  by  what  is  called  the  process  of  Liquation :  this  con- 
sists in  melting  the  two  metals  with  a  large  proportion  of  lead,  and  cooling 
the  mixture  suddenly  in  the  form  of  cakes ;  these  are  then  exposed,  on  an  in- 
clined hearth,  to  a  temperature  sufficient  to  melt  the  lead,  but  not  the  copper, 
when  the  former  metal  runs  off,  and  carries  all  the  silver  with  it,  leaving  the 
solid  copper  behind. 

643.  Cupellation  — Silver  is  parted  from  lead  by  a  process  termed 
Cupellation.     It  consists  in  exposing  the  mass,  in  the  first  instance,  to  a  red- 
heat,  upon  the  hearth  of  a  shallow  furnace,  while  a  current  of  air  is  caused  to 
play  upon  its  surface ;  the  lead  rapidly  oxydizes,  and  is  converted  into  lith- 
arge, which,  in  turn,  melts  and  runs  off,  leaving  the  metallic  silver  unoxyd- 
ized,  and  in  a  nearly  pure  state  (refined  silver).     The  hearth  upon  which  this 
operation  is  conducted,  is  called  a  cupel,  and  is  formed  by  molding  pulverized 
bone-ashes  into  the  shape  of  an  oval,  shallow  basin. 

In  order  to  render  the  silver  thus  obtained  still  purer 
(fine  silver),  it  is  again  fused  under  the  same  circum- 
stances in  small  cupels  (Fig.  202) ;  by  which,  the  last  ^ 
remaining  traces  of  lead,  and  all  other  metallic  impur-: 
ities,  except  gold,  are  converted  into  oxyds,  and  ab- 
sorbed by  the  porous  bone-ash. 

644.  Properties . — Silver  has  the  clearest  white  color  of  all  the  metals. 
It  is  malleable  and  ductile  in  a  high  degree,  and  in  hardness  is  intermediate 
between  gold  and  copper.     It  melts  at  a  bright  red-heat,  1873°  F.,  expand- 
ing forcibly  at  the  moment  of  solidification ;  and  is  not  oxydized  by  exposure, 
at  any  temperature,  to  either  a  dry  or  moist  atmosphere.     Pure  silver,  how- 
ever, possesses  the  remarkable  property  of  mechanically  absorbing  oxygen, 
when  melted,  to  the  extent  of  many  times  its  volume.     This  oxygen  is  again 
disengaged  at  the  moment  of  solidification,  and  gives  rise  to  the  peculiar  ar- 
borescent appearance  often  noticed  on  the  surface  of  masses  of  silver.      Silver 
has  a  powerful  affinity  for  sulphur ;  and  when  exposed  to  air  containing  very 
minute  quantities  of  sulphurous  acid,  or  sulphuretted  hydrogen,  it  soon  be- 
comes superficially  blackened  or  tarnished,  from  the  formation  of  a  thin  film 
of  sulphide  upon  its  surface.* 

The  best  solvent  of  silver  is  nitric  acid,  which  acts  upon  the  metal  with 
great  rapidity;  if  the  silver  contains  any  gold,  it  will  be  left  undissolved  as  a 
dark  powder.  Solution  of  silver  coin  in  nitric  acid  appears  of  a  bluish-green, 
color,  from  the  copper  it  contains.  Hydrochloric  acid  scarcely  acts  upon  silver, 
and  sulphuric  acid  only  when  hot. 

*  The  air  of  large  towns  or  cities,  and  the  air  of  rooms  in  which  mineral  coal  or  coal- 
pas  is  burnt,  always  contains  sufficient  of  the  gaseous  compounds  of  sulphur  to  gradually 
tarnish  silver. 

QUESTIONS. — How  is  silver  obtained  by  amalgamation  freed  from  copper?  What  is  this 
process  termed  ?  How  is  silver  freed  from  lead  ?  What  is  a  cupel  ?  What  are  the  propr 
erties  of  silver  ?  What  are  the  relations  of  fused  silver  and  oxygen  ?  What  of  silver  and 
sulphur  ?  What  are  the  solvents  of  silver  ? 


390  I-NORQANIC     CHEMISTRY. 

645.  0  x  y  d  s    of    Silver. — Silver  forms  three  oxycft — the  suboxyd, 
AgsO  ;  the  protoxyd,  AgO ;  and  a  peroxyd,  AgO* 

646.  Protoxyd    of    Silveris  the  only  oxyd  which  forms  permanent 
salts,  and  may  be  procured"  by  adding  potash  or  soda  to  a  solution  of  the 
nitrate,  or  any  soluble  salt  of  silver.     It  is  a  dark-brown  or  black  powder, 
soluble  in  ammonia,  and  to  a  slight  extent  in  pure  water.     Its  solution  in 
cyanide  of  potassium  constitutes  the  silver  solution  used  in  electro-plating. 
Oxyd  of  silver  is  decomposed  at  a  temperature  below  red  heat,  and  to  some 
extent  also  by  the  action  of  solar  light. 

647.  Nitrate   of  Silver,    A  g  0  ,  N  Os. — This  is  the  most  important 
of  the  salts  of  silver,  and  may  be  obtained  in  the  form  of  colorless,  transparent, 
tabular  crystals,  by  dissolving  silver  in  nitric  acid,  and  evaporating  the  solu- 
tion to  dryness.     The  crystals  thus  obtained  are  readily  soluble  in  water,  and 
when  fused  and  cast  into  slender  sticks,  they  constitute  the  lunar  caustic  of 
the  surgeon.* 

Nitrate  of  silver,  when  perfectly  pure,  undergoes  no  change  by  the  action 
of  light,  but  when-  exposed  to  light  in  contact  with  organic  matter,  it  blackens 
rapidly.  Stains  thus  produced  by  it  can  not  be  removed  by  washing  with 
soap  and  water ;  hence  nitrate  of  silver  constitutes  an  essential  ingredient  in 
the  composition  of  hair-dyes,  and  the  indelible  inks  used  for  marking  linen. 
Ivory,  marble,  and  other  bodies,  may  be  stained  a  permanent  black  by  soak- 
ing hi  a  solution  of  this  salt,  and  then  exposing  to.  the  direct  action  of  the 
sun's  rays.  The  black  coloring  matter  is  by  some  supposed  to  be  silver  in 
a  state  of  fine  division,  and  by  others  to  be  a  suboxyd  of  silver.  It  may  be 
removed  from  the  hands,  or  from  linen,  by  the  employment  of  a  strong  so- 
lution of  iodide  of  potassium,  or  more  easily  by  cyanide  of  potassium.  Ni- 
trate of  silver  is  sometimes  given  as  a  medicine  ;  if  the  administration  of  it 
is  long  continued,  a  portion  of  the  silver  in  combination  tends  to  find  its  way 
out  of  the  system  at  the  surface  of  the  body ;  but  becoming  decomposed  by 
the  action  of  light  before  it  reaches  the  outer  surface  of  the  skin,  it  imparts 
to  all  those  portions  of  the  body  exposed  to  light  a  singular  blue  or  lead-gray 
color.  This  color,  from  the  circumstance  that  it  is  formed  below  the  outer 
skin  (or  cuticle),  is  perfectly  indelible,  f 


*  The  corrosive  power  of  lunar  caustic  is  not  the  result  of  any  specific  action  of  the 
nitrate  of  silver  but  of  the  nitric  acid,  which  is  liberated  by  the  decomposition  of  the 
salt  when  in  contact  with  organic  matter. 

t  A  most  singular  case  of  this  discoloration  was  to  be  seen  a  few  years  since  in  the  city 
of  New  York,  in  the  person  of  an  itinerant  book-agent,  who  was  familiarly  called  the 
"  blue  man."  The  color  of  this  person,  owing  to  an  injudicious  use  of  nitrate  of  silver 
as  a  remedy  for  epilepsy,  was  generally  of  a  dark,  dull  blue,  varying  to  brown  with  shades 
of  green. 

QUESTIONS— What  oxyds  of  silver  are  there  ?  What  is  the  principal  oxyd  ?  How  is 
it  prepared  ?  What  are  its  properties  ?  How  is  nitrate  of  silver  prepared  ?  What  is  lu- 
nar caustic  ?  What  action  has  light  upon  this  salt  ?  Into  what  articles  does  it  enter  as  an 
essential  ingredient?  How  may  nitrate  of  silver  stains  be  removed?  What  sometimes 
happens  wneu  nitrate  ot  silver  is  taken  into  the  system  ? 


SILVER.  391 

"When  a  stick  of  phosphorus  is  introduced  into  a  solution  of  nitrate  of 
silver,  it  soon  becomes  incrusted  with  arborescent  crystals  of  the  metal.  Th0 
introduction  of  mercury  into  a  solution  of  nitrate  of  silver  also  precipitates 
the  metal  in  beautiful  tree-like  forms  which  are  called  arbor  Diancc.  Metallic 
copper  at  once  throws  down  metallic  silver  from  solutions  of  the  nitrate, 
and  forms  nitrate  of  copper. 

648.  Chloride   of    Silve  r  a   A  g  C 1 , — This  compound  appears  as  a 
white,  curdy  precipitate  when  hydrochloric  acid,  or  the  solution  of  any  chlo- 
ride (as  common  salt)  is  added  to  a  solution  of  silver.     Its  formation,  under 
these  circumstances,  constitutes  a  most  delicate  test  for  the  presence  of  silver 
in  solution,  as  the  chloride  of  silver  is  so  entirely  insoluble  in  water,  that  a 
millionth  part  of  it  will  occasion  a  cloudiness  of  the  solution.      It  is,  however, 
readily  soluble  in  ammonia,  and  when  exposed  to  the  light,  quickly  assumes 
a  violet  color.     Chloride  of  silver,  kept  in  solution  by  the  alkaline  chlorides, 
probably  exists  in  minute  quantities  in  all  sea- water.     MM,  Malagutti  and 
Durocher,  eminent  French  chemists,  have  estimated,  on  the  basis  of  recent 
experiments,  that  each  cubic  mile  of  sea-water  contains  10£  Ibs.  of  silver  in 
the  form  of  chloride. 

649.  Uses  , — Pure  silver,  by  reason  of  its  softness,  is  not  used  to  any  ex- 
tent in  the  arts ;  but  for  coin,  plate,  etc.,  it  is  always  alloyed  with  a  propor- 
tion of  copper,  which  greatly  increases  its  hardness  without  materially  dimin- 
ishing its  whiteness,  and  thus  renders  it  less  liable  to  be   worn  by  use. 
The  amount  of  copper  that  may  be  alloyed  with  silver  for  the  manufacture  of 
coin  is  always  regulated  by  government.     In  Great  Britain,  standard  silver 
is  composed  of  11  parts  of  silver  and  1  of  copper;  in  the  United  States,  all 
gold  and  silver  coin  consists  of  nine  tenths  pure  metal  and  one  tenth  alloy. 
In  England  and  France,  the  government  also  regulates  the  purity  of  silver 
used  for  the  manufacture  of  plate  j  in  the  United  States  the  manufacturer 
alloys  his  silver  at  discretion. 

Silver  is  frequently  employed  to  give  a  coating  to  less  expensive  metals. 

Plating  on  copper  is  effected  by  laying  a  strip  of  silver  upon  a  bar  of  cop- 
per, and  uniting  the  two  metals  (without  solder)  by  hammering  and  rolling 
at  a  temperature  just  below  the  fusing  point  of  silver.  The  compound  ingot  is 
then  rolled  to  the  required  degree  of  tenuity.  Silvering,  or  covering  the  sur- 
face of  brass  or  copper  with  a  thin  coating  of  silver,  may  be  effected  by  first 
thoroughly  cleaning  the  surface  to  be  silvered  by  momentary  immersion  in 
nitric  acid,  and  then  rubbing,  with  a  mixture  of  cream  of  tartar  (100  parts), 
chloride  of  silver  (10  parts),  and  corrosive  sublimate  (1  part);  the  surface  is 
afterwards  polished.  It  is  in  this  way  that  thermometer  scales  are  silvered. 
A  peculiar  blanched  or  "  dead"  appearance  may  be  given  to  articles  manufac- 
tured from  an  alloy  of  silver  and  copper,  by  boiling  them  in  a  solution  of  bi- 

QUF.STIONS — What  is  said  of  chloride  of  silver  ?  What  is  a  test  of  the  presence  of  sil- 
ver in  solution  ?  Does  silver  exist  in  sea-water  ?  In  what  state  is  silver  used  in  the  arts  ? 
What  is  standard  silver  in  Great  Britain  and  the  United  States  ?  How  is  plating  effected  ? 
How  may  articles  be  silvered  ?  What  is  dead  silver  ? 


392 


INOKGANIC     CHEMISTKY. 


FlG.  203. 


Flft,  204. 


sulphate  of  potash;  the  acid  of  which  dissolves  out  the  copper  from  the  sur- 
face, and  leaves  the  particles  of  silver  isolated. 

650.  Silvering  of  Glass . — Certain  organic  substances,  such  as  oil 
of  cassia,  oil  of  cloves,  or  solution  of  grape-sugar,,  possess'  the  property,  when 
added  to  certain  salts  of  silver  in  solution,  of  precipitating  the  silver  in  the 
state  of  bright,  lustrous  metal     This  principle  has  been  recently  applied  to 
the  silvering  of  glass ;  and  many  articles  of  great  beauty,  such  as  mirrors, 
glass-globes,  vases,  door-knobs,  etc.,  are  now  coated  in  this  manner,* 

SECTION    III. 

GOLD, 

Equivalent,  98 -T.     Symbol,  Au.  (Auram).     Specific  gravity,  19.2. 

651.  Natural    History    and    Distribution , — Gold   is  always 
found  native  or  in  the  metallic  state ;  generally  in  the  form  of  thin  scales-  or 

grains,  sometimes  as  large,  nodular  masses,  f  and  some- 
times in  crystals;  the*  last  being  al- 
ways modifications  of  the  cube,  or 
octohedron.  (See  Pigs,  203  and  204.) 
Native  gold  is  always  alloyed  with 
silver,  and  is  often  associated  with  small 
quantities  of  osmium,  indium,  copperr 
antimony,  sulphuret  of  iron,  and  rarely 
with  tellurium.  No  regular  veins  of 
gold  are  met  with  (what  are  called  veins  of  gold  being: 
merely  veins  of  quartz  containing  disseminated  metallic  particles).  It  com- 
monly occurs  in  the  most  ancient  rocks>  or  in  the  alluvial  deposites  of  rivers, 
As  gold  is  found  naturally  in  a  metallic  state,  the  operations  for  obtaining  it 
are  almost  purely  mechanical,  as  washing,  etc.  "When  the  gold  is  very  finely 
divided  and  mixed  with  earthy  matters  or  other  metals,  it  is  separated  by  a 
process  of  amalgamation  similar  to  that  already  described  for  obtaining  silver. 
(See  §  641.)  

*  A  composition  for  silvering-  glass  may  be  prepared  as  follows  r— Mix  30  grains  aqna 
ammonia,  60  nitrate  of  silver  (crystals),  90  spirits  of  wine,  and  90  of  water.  When  the 
nitrate  of  silver  is  completely  dissolved,  filter  the  liquid  and  add  15  grains  of  grape  sngar 
dissolved  in  a  mixture  of  H  ounces  of  water  and  1£  ounces  spirits  of  wine.  For  silvering 
a  glass,  it  is  sufficient  to  leave  this  solution  in  contact  with  the  glass  for  a  space  of  two  or 
three  days ;  but  by  heating  the  mixture,  the  effect  may  be  produced  rapidly. 

f  A  mass  of  gold  once  found  in  North  Carolina  weighed  28  pounds;  a  mass  found  in 
the  Ural  Mountains,  and  now  in  the  Imperial  Cabinet  of  St.  Petersburgh,  has  a  weight  of 
nearly  80  pounds.  Masses,  however,  of  larger  size,  mingled  with  quartz,  have  been  since 
found  in  both  California  and  Australia. 


QUESTIONS. — How  may  glass  be  silvered  ?  What  is  said  of  the  natural  occurrence  of 
gold  ?  What  metals  usually  occur  associated  with  it?  How  is  gold  obtained  from  the 
earth? 


GOLD.  393 

652.  Properties  . — Gold  possesses  a  characteristic  yellow  color  and  a 
high  metallic  luster.     It  is  the  most  malleable  of  all  the  metals,  and  may  be 
beaten  into  leaves  which  do  not  exceed  1-200, 000th  of  an  inch  in  thickness, 
It  also  possesses  a  high  degree  of  tenacity,     When  pure,  gold  is  nearly  as 
soft  as  lead,     It  fuses  at  a  temperature  of  2016°  F.,  and  can  not  be  advan- 
tageously employed  for  castings,  as  it  shrinks  greatly  in  solidifying,     Gold 
does  not  combine  directly  with  oxygen  at  any  temperature  ;  none  of  the  sim- 
ple acids,  with  the  exception  of  the  selenic,  have  any  effect  upon  it ;  neither 
has  sulphur  or  sulphuretted  hydrogen,     Chlorine  and  bromine  attack  it  easily, 
and  it  is  dissolved  by  any  solution  that  liberates  chlorine.     The  most  usual 
solvent  of  gold  is  aqua,  regia.     (See  §  361.) 

653.  Compounds    of   Gold  .—There  are  two  oxyds  of  gold,  « prot* 
oxyd,  AuO,  and  a  peroxyd,  or  auric  acid,  AuOg,     Both  are  unstable  com- 
pounds, and  are  decomposed  by  the  action  of  light,     With  chlorine,  also, 
gold  unites  in  two  proportions  to  form  a  protochloride,  AuCl,  and  a  perchlo- 
ride, AuCl3.     The  last  is  the  most  important  compound  of  gold,  and  is  always 
produced  when  gold  is  dissolved  in  nitromuriatic  acid, 

By  cautiously  evaporating  the  solution  of  gold  in  aqua  regia,  the  perchloride 
may  be  obtained  in  the  form  of  yellow  crystals,  soluble  In  water,  alcohol,  and 
ether.  If  a  solution  of  crystallized  chloride  of  gold  be  applied  to  the  skin,  or 
any  other  organic  substance,  it  imparts  to  it,  on  drying,  a  purple-colored  stain, 
If  a  few  drops  be  added  to  a  dilute  solution  of  protochloride  of  tin,  a  most 
beautiful  purple  precipitate  is  formed,  which  is  known  as  the  purple  of  Cos- 
silts.  This  compound  of  gold  and  tin  is  extensively  used  in  enamel  and  por- 
celain painting,  and  also  for  imparting  to  glass  a  rich  rose  or  purple  color. 

Polished  steel  dipped  into  an  ethereal  solution  of  perchloride  of  gold,  decom- 
poses it,  and  becomes  covered  with  a  coat  of  metallic  gold :  delicate  cutting 
instruments  are  gilt  in  this  way.  Silk  ribbons  may  be  also  gilt  by  moistening 
them  with  this  solution,  and  exposing  them  to  a  current  of  hydrogen,  or  phos- 
phuretted  hydrogen  gas. 

Ammonia  added  to  a  solution  of  chloride  of  gold,  produces  a  yellowish- 
brown  precipitate,  aurate  of  ammonia,  or  fulminating  gold]  this  compound 
explodes  at  a  moderate  heat,  or  by  friction. 

654.  Industrial   Uses   of   Gold  . — Gold  intended  for  coin  and  most 
other  purposes,  is  always  alloyed  with  a  certain  proportion  of  silver  or  cop- 
per, in  order  to  increase  its  hardness  and  durability,     Gold  for  coinage  is 
usually  alloyed  with  copper  to  the  amount  of  about  10  per  cent. 

The  quantity  of  pure  gold  contained  in  a  given  mass  is  expressed  by  the 
word  caret,  used  in  reference  to  a  certain  standard  number ;  which  number  in 
the  United  States  ia  24.  Thus,  perfectly  pure  gold  is  said  to  be  24  carats 


QUESTIONS.— What  are  the  characteristic  properties  of  gold  ?  AVhat  is  said  of  its  rela- 
tions to  oxygen  ?  What  of  its  solubility  ?  What  are  the  principal  compounds  of  gold  ? 
How  is  perchloride  of  gold  prepared?  What  are  its  properties  ?  What  is  the  "purple 
of  Cassius?"  How  is  steel  gilded?  What  is  fulminating  gold?  In  what  condition  is 
gold  used  in  the  arts  ?  How  is  the  purity  of  gold  expressed  ? 

17* 


394  INORGANIC     CHEMISTRY. 

fine;  when,  on  the  other  hand,  gold  is  spoken  of  as  18  carats  fine,  it  is  under- 
stood that  the  mass  consists  of  18  parts  (three  fourths)  gold,  and  6  parts  (one 
fourth)  alloy. 

The  determination  of  the  amount  of  pure  gold  or  silver  in  a  given  mass  of 
metal,  is  called  assaying  ;  and  as  the  value  of  all  the  various  gold  and  silver 
coins  in  the  world  is  regulated  by  the  operation,  the  various  processes  con- 
tained in  this  department  of  chemistry  have  been  earned  to  a  high  degree  of 
perfection. 

655.  Preparation  of  Fine   Gold  .-"-The  process  of  obtaining  fii  . 
gold,  or  of  separating  gold  from  its  alloys  of  silver  and  copper,  depends  upon 
the  solubility  of  silver  and  copper  in  nitric  acid,  and  the  perfect  insolubility  of 
gold4n  the  same  liquid.     In  order  to  effectually  carry  out  the  operation,  it  is 
necessary  that  the  silver  should  amount  to  at  least  three  times  the  weight  of 
gold,  or  otherwise  portions  of  silver  will  be  mechanically  protected  from  the 
action  of  the  acid,  and  the  separation  be  incomplete.     If,  therefore,  the  alloy 
be  found  to  contain  more,  than  one  fourth   of  its  weight  of  gold,  sufficient 
silver  is  added  to  reduce  it  to  this  proportion ;  and  hence  this  method  of  part- 
ing the  metals  is  known  in  assaying  as  quartatton.     The  gold  remaining  un- 
dissolved  hi  the  acid  is  collected  and  melted  into  ingots,  while  the  silver  is 
separated  from  the  copper  in  solution  by  precipitation  with  common  salt  as  a 
chloride,  and  subsequently  reduced  by  contact  with  metallic  zinc.     The  sepa- 
ration of  gold  from  its  alloys  may  also  be  effected  by  boiling  the  gold  in  sul- 
phuric acid,  which  dissolves  the  silver  and  the  copper,  but  leaves  the  gold 
unchanged. 

"When  a  solution  of  protosulphate  of  iron  is  added  to  a  solution  of  perchloride 
of  gold,  metallic  gold  is  precipitated  in  the  form  of  a  fine  brown  powder,  which, 
when  diffused  in  water  and  viewed  by  transmitted  light,  appears  green ;  the 
gold  thus  obtained  is  perfectly  pure,  and  appears  dark,  by  reason  of  its  ex- 
treme subdivision.  "When  rubbed  and  pressed,  it  regains  its  characteristic  color. 

656.  Gold   Leaf  is  manufactured  by  first  forging  the  gold  into  plates, 
and  rolling  them  into  thin  ribbons  by  means  of  steel  rollers.     The  ribbon  is 
then  divided  into  small  squares,  which  are  placed  between  leaves  or  sheets  of 
gold-beaters'  skin  (a  thin  membraneous  substance  obtained  from  the  intestines 
of  animals),  and  the  whole  beaten  with  a  heavy  hammer.     As  the  gold  ex- 
pands, it  is  divided  and  subdivided  until  the  required  thinness  of  leaf  is  ob- 
tained. 

The  commercial  value  of  pure  silver  is  about  $16  per  pound;  a  dollar  coin 
weighs  an  ounce  troy.  The  value  of  fine  gold  is  about  fifteen  times  greater 
than  that  of  silver,  an  ounce  being  worth  from  sixteen  to  eighteen  dollars. 

Bullion  is  the  term  applied  to  gold  and  silver  reduced  from  the  ore,  but  not 
yet  manufactured ;  at  the  mint  it  means  all  gold  and  silver  suitable  for  coin- 
age. 

QUESTIONS.—  What  is  meant  by  gold  18  carata  fine  ?  What  is  assaying  ?  How  is  gold 
parted  from  its  alloys  ?  What  is  understood  by  qtiartation?  How  may  brown  metallic 
gold  be  obtained  ?  How  is  gold  leaf  manufactured?  What  is  the  comparative  value  of 
silver  and  gold  ?  What  is  bullion  ? 


PLATINUM.  395 

SECTION     IT. 

PLATINUM,    PALLADIUM,    RHODIUM,    RUTHENIUM,    OSMIUM,   IRIDIUM. 

657.  Platinum , — Equivalent,  98'7. ;  Symbol,  Ft. ;  Specific  gravity,  21'5. 
— Platinum  (little  silver)  is  not  an  abundant  metal,  and  is  always  found  na- 
tive, usually  in  the  form  of  small  flattened  grains,  but  sometimes  in  nodular 
masses  of  considerable  size.     It  is  very  rarely  met  with  imbedded  in  rock, 
but  is  always  obtained  from  alluvial  deposites  (sand,  etc.)  by  washing.     Tho 
principal  localities   which  furnish  platinum  are  situated  upon  the  western 
slope  of  the  Ural  mountains  in  Russia,  in  Brazil,  and  Borneo.     It  was  first 
recognized  as  a  distinct  metal  about  the  middle  of  the  last  century  (1749). 

658.  Properties  . — Platinum  is  a  grayish- white  metal,  intermediate  in 
hardness  between  copper  and  iron;  it  exceeds  in  tenacity  all  the  metals  ex- 
cept iron  and  copper,  and  is  only  inferior  in  ductility  to  gold  and  silver.     It 
may  also  be  beaten  into  thin  laminae  like  gold  leaf,  and  at  a  white-heat  may 
be  welded  like  iron.     The  most  valuable  property,  however,  of  platinum,  is  its 
infusibility,  which  is  so  great  that  it  resists  the  most  intense  heat  of  a  wind 
furnace,  and  only  yields  to  the  heat  generated  by  the  oxy hydrogen  blow-pipe, 
or  the  voltaic  battery.     It  alloys  readily  with  lead,  iron,  and  many  other 
metals ;  and  the  compounds  thus  formed  are  much  more  fusible  than  pure 
platinum.     Care,  therefore,  must  be  taken  in  using  platinum  crucibles,  not  to 
heat  in  them  oxyds  of  fusible  and  easily-reduced  metals,  as  lead,  tin,  bismuth, 
etc. ;  since,  in  the  event  of  the  reduction  of  the  oxyd,  -the  crucible  would  be 
destroyed  by  the  formation  of  a  fusible  alloy. 

Platinum  does  not  oxydize  in  the  air  at  any  temperature,  and  none  of  the 
simple  acids  have  an  effect  upon  it.  Aqua  regia  dissolves  it,  but  less  readily 
than  gold ;  and  it  is  also  corroded  by  heating  to  redness  in  contact  with  tho 
caustic  alkalies,  or  with  phosphoric  acid  in  the  presence  of  carbon. 

The  great  infusibility  of  platinum,  and  its  power  of  resisting  chemical 
agents,  give  it  a  high  value  as  a  material  for  the  construction  of  apparatus  to 
be  used  in  the  manufacture  of  powerful  acids,  and  in  chemical  analysis.  It  is 
also  extensively  employed  by  dentists  for  tho  setting  of  artificial  teeth,*  and 
to  some  extent  for  the  bushing  of  the  touch-holes  of  guns.  An  attempt  was 
made  in  Russia  some  years  since  to  employ  platinum  for  coinage,  but  it  was 
found  to  be  inconvenient,  and  the  experiment  has  now  been  abandoned.  The 
value  of  crude  platinum  is  about  half  that  of  gold ;  but  in  its  manufactured 
state  it  sells  for  from  $18  to  $20  per  ounce. 

The  process  employed  for  working  it  depends  upon  its  property  of  welding 


*  The  value  of  the  platinum  annually  required  for  this  purpose  at  the  present  time  in 
this  country,  is  estimated  at  $150,000. 

QUESTIONS How  is  platinum  found  in  nature?    What  nre  its  principal  localities? 

When  was  it  discovered  ?  What  are  the  general  properties  of  platinum  ?  What  is  said 
of  its  infusibility  ?  What  of  its  alloys  ?  What  of  its  solubility  ?  What  are  its  industrial 
uses  ?  How  is  it  manufactured  ? 


396  INORGANIC     CHEMISTRY. 

at  high  temperatures.  The  crude  grains  are  first  purified  by  dissolving  in 
aqua  regia  and  precipitating  as  chloride  of  platinum,  which  is  subsequently  re- 
duced to  a  metallic  state  by  heat  It  is  then,  in  connection  with  scrap  pla- 
tinum, fused  into  little  ingots  by  the  oxyhydrogen  blow-pipe,  and  these  are 
subsequently  welded  and  rolled  into  bars  or  sheets.  The  working  of  it  was 
formerly  confined  wholly  to  France,  but  within  a  few  years  past  it  has  been 
introduced  somewhat  extensively  as  a  business  in  this  country. 

Platinum  exists  in  two  states  of  minute  subdivision,  viz.,  as  spongy  platinum, 
and  platinum  black.  The  properties  and  preparation  of  spongy  platinum  have 
been  already  described  (§§  48,  296).  Platinum  black  is  the  metal  in  a  state 
of  such  fine  subdivision,  that  it  has  the  appearance  of  soot.  It  is  easily  pre- 
pared by  slowly  heating  to  212°  F.,  with  frequent  agitation,  a  solution  of 
chloride  of  platinum,  to  which  an  excess  of  carbonate  of  soda  and  a  quantity 
of  sugar  have  been  added.  The  precipitated  black  powder  is  collected  on  a  filter, 
•washed  and  dried.  Platinum  black  possesses  the  power,  in  a  much  higher 
degree  than  spongy  platinum,  of  condensing  gases,  and  oxydking  alcohol  and 
ether  (§  469). 

659.  Platinum  forms  two  oxyds,  PtO  and  PtO2,  and  two  chlorides,  PtCl 
and  PtCI?.  The  last  named  compound,  the  bi-chloride  of  platinum,  is  the 
most  important  soluble  salt  of  platinum,  and  is  always  formed  when  platinum 
is  digested  in  aqua  regia.  Its  crystals,  obtained  by  evaporating  its  acid  solu- 
tion, form  with  water  a  rich  orange-colored  liquid,  which  is  much  valued  in 
chemistry  as  the  only  reagent  which  precipitates  potassa  from  its  solutions. 

660.  Palladium,  Rhodium.  Ruthenium,  Osmium,  and 
Indium, — These  metals  are  found  only  in  exceedingly 
small  quantities,  and  usually  occur  associated  with  pla- 
tinum, which  metal  they  resemble  generally  in  their  prop- 
erties. 

Pattadium  is  a  white  metal,  more  brilliant  than  platinum,  very  infusible, 
malleable,  and  ductile.  Its  hardness,  whiteness,  and  inalterability  would  ren- 
der it  exceedingly  valuable  in  the  arts  if  it  could  be  obtained  in  sufficient 
quantities.  The  Eoyal  Geological  Society  of  Great  Britain  award  a  medal  of 
palladium  for  eminent  discoveries  in  this  department  of  science.  Iridium  is 
found  alloyed  with  osminm,  very  often  in  California  gold,  forming  the  mineral 
iridosmine,  which  is  the  hardest  of  all  known  alloys.  Indium  is  a  white,  hardT 
Iwittle  metal,  more  infusible  than  platinum,  and  is  the  heaviest  of  all  substances, 
being  nearly  22  times  heavier  than  an  equal  bulk  of  water.  It  has  been,  used 
to  some  extent  for  forming  the  tips  of  gold  pens. 

QUESTIONS. — In  what  two  states  of  subdivision  does  metallic  platinum  exist  ?  GITB  the 
properties  of  spongy  platinum.  How  is  platinnm  black  prepared?  What  compounds 
does  platinum  form  ?  What  is  its  most  soluble  salt  ?  For  what  reaction  is  bi-chloride  of 
platinum  distinguished  ?  What  is  said  of  the  other  metals  included  in  the  group  of  noble 
metals  ?  What  of  palladium  ?  What  of  iridium  ? 


PHOTOGRAPHY.  397 

CHAPTER     XV. 


661.  Photography  (light-drawing)  is  the  art  of  drawing, 
or  producing  pictures,  or  copies  of  objects,  by  the  action 
of  light  upon  certain  chemical  preparations. 

The  whole  art  is  based  upon  the  circumstance,  that  the  chemical  element 
of  the  solar  ray  is  capable  of  blackening  or  discoloring  certain  compound  sub- 
stances exposed  to  its  influence,  the  principal  of  which  are  various  salts  of 
silver.*  This  fact  has  been  long  known  and  recognized,  and  as  far  back  as 
1802,  Sir  Humphrey  Davy  .succeeded  in  obtaining  images  upon  paper  or 
white  leather  prepared  with  nitrate  of  silver,  by  exposure  in  a  camera  ob- 
Bcura ; — the  parts  of  the  surface  subjected  to  a  strong  light  being  blackened, 
wliile  those  in  the  shadow,  which  were  unacted  upon,  remained  white.  It  was 
found,  however,  impossible  to  arrest  the  action  thus  generated,  and  the  image 
formed  soon  disappeared  by  a  continuous  darkening  of  the  whole  surface. 
The  subject  appears  to  have  been  next  taken  up  by  M.  Niepce,  a  French 
gentleman  of  Chalons,  who  ascertained,  hi  1823,  that  when  a  surface  of  a  pe- 
culiar kind  of  bitumen,  known  as  "Jew's  pitch,"  was  exposed  in  a  camera, 
that  the  parts  strongly  acted  upon  by  light  became  insoluble  in  oil  of  laven- 
der, while  those  unacted  upon,  or  influenced  by  weaker  rays,  retained  their 
solubility  in  a  greater  or  less  degree,  and  could  consequently  be  dissolved  off, — 
thus  forming  an  imperfect  picture.  This,  and  other  interesting  facts,  Niepce 
laid  before  the  Eoyal  Society  of  Great  Britain  in  1827,  but  they  attracted  little 
attention,  and  in  1829  he  formed  a  partnership  with  a  French  artist  by  the 
name  of  Daguerre  (who  was  engaged  in  experimenting  on  the  same  subject), 
for  the  future  joint  prosecution  of  their  investigations.  Niepc6  died  hi  1833, 
but  Daguerre  continued  his  experiments,  and  in  1 839  first  exhibited,  as  the 
result  of  his  labors,  the  pictures  since  called  in  his  honor  Daguerreotypes. 
His  process  was  at  first  kept  secret,  but  was  soon  purchased  by  the  French 
Government  and  made  known  to  the  world — a  pension  of  6,000  francs  being 
awarded  to  Daguerre,  and  one  of  4,000  to  the  son  of  Niepce.  It  is  also  a 
very  singular  fact,  that  substantially  the  game  results  made  known  by 
Daguerre,  were  also  discovered  at  about  the  same  time  by  Mr.  Talbot,  an 


*  The  influence  of  light  in  producing  the  coloration  of  fruit  may  be  rery  prettily  illus- 
trated by  pasting  letters  cut  in  paper  upon  the  surface  of  a  ripening  peach  exposed  to  the 
snn.  After  the  lapse  of  a  few  days  the  characters  will  be  found,  on  removing  the  paper, 
to  be  distinctly  marked  in  white,  on  a  red,  or  yellow  ground. 

QUESTIONS. — What  is  photography?  Upon  what  does  the  art  depend?  What  were 
come  of  the  earliest  photographic  experiments?  What  were  Niepce' s  experiments? 
Under  what  circumstances  was  the  daguerreotype  process  discovered  and  made  known  ? 


398  INORGANIC     CHEMISTRY. 

English  gentleman,  who  had  been  engaged  in  investigating  the  chemical  re- 
lations of  light  for  a  number  of  years  previous. 

662.  Daguerreotype  Process  , — The  essential  features  of  the 
daguerreotype  process,  as  discovered  by  Daguerre  and  now  practised,  are  as 
follows :  a  highly  -polished  tablet  of  silver  (copper-plated)  is  selected  as  the 
basis  of  the  picture,  and  exposed  to  the  vapor  of  iodine.  The  iodine  rapidly 
attacks  the  silver,  and  forms  over  its  surface  a  thin  yellow  film  of  iodide  of 
silver,  which  is  so  exceedingly  sensitive  to  the  action  of  light,  that  it  is  almost 
instantly  decomposed  by  it.*  The  plate  thus  prepared,  and  carefully  pro-, 
tected  from  the  light,  is  then  exposed  to  the  image  formed  by  the  lens  of 
a  camera  obscura.  Relatively  the  quantity  of  the  light-producing  principle, 
and  the  quantity  of  the  chemical  principle  reflected  from  any  object  are  the 
same ;  therefore,  as  the  light,  and  shadows  of  the  luminous  image  vary,  so 
will  the  power  of  producing  change  upon  the  plate  vary,  and  the  result  will 
be  the  production  of  a  picture  which  will  be  a  faithful  copy  of  nature,  with 
reversed  lights  and  shadows;  the  lights  darkening  the  plate,  while  the 
shadows  preserve  it  white,  or  unaltered.  The  time  required  for  producing 
the  impression  may  vary  from  1  to  60  seconds,  according  to  the  brightness  or 
clearness  of  the  atmosphere,  and  the  time  of  day. 

If  the  picture  thus  formed  were  left  without  further  care,  it  would  soon 
fade  away,  and  no  trace  of  it  would  appear  on  the  surface  of  the  plate.  In 
practice,  the  plate  is  not  exposed  to  the  influence  of  light  sufficiently  long  to 
form  upon  its  surface  an  image  visible  to  the  eye,  but  the  picture  is  developed, 
or  brought  out  and  rendered  permanent,  by  exposure  to  the  vapor  of  mer- 
cury. This  metal,  in  a  state  of  very  fine  division,  is  condensed  upon  and  ad- 
heres to  those  portions  of  the  surface  of  the  plate  which  have  been  affected 
by  the  light.  Where  the  shadows  are  deep,  there  is»  scarcely  a  trace  of  mer- 
cury ;  but  where  the  lights  are  strong,  the  metallic  dust  is  deposited  of  con- 
siderable thickness.  This  deposition  of  mercury  essentially  completes  and 
fixes  the  picture. 

The  reason  why  the  vapor  of  mercury  attaches  itself  only  to  those  portions 
of  the  plate  which  have  been  affected  by  the  chemical  influence  of  light  is  not 
definitely  known :  in  ah1  probability,  we  have  involved  the  action  of  several 
forces.  It  is  not,  however,  necessary  that  a  surface  should  be  chemically  pre- 
pared to  exhibit  these  results.  A  polished  plate  of  metal,  a  piece  of  marble, 
of  glass,  or  even  wood,  when  partially  exposed  to  the  action  of  light,  will, 
when  breathed  upon,  or  presented  to  the  action  of  mercurial  vapor,  show  that 
a  disturbance  has  been  produced  upon  the  portions  which  were  illuminated ; 
whereas  no  change  can  be  detected  upon  the  parts  kept  in  the  dark. 

The  next  step  of  the  process  is  to  remove  from  the  plate  any  iodide  of 
silver  which  may  remain  unacted  upon,  and  which  would  be  liable  to  change 

*  Bromine  forms  a  coating  even  more  sensitive  than  iodine,  and  is  now  extensively  used 
in  its  place. 

QUESTIONS.— What  is  the  first  step  of  this  process  ?  What  the  second  ?  Why  does  the 
vapor  of  mercury  develop  the  picture  ?  What  is  the  concluding  part  of  the  process  ? 


PHOTOGRAPHY.  399 

on  exposing  the  plate  to  light,  This  is  effected  by  dipping  the  plato  into  a 
solution  of  hyposulphite  of  soda,  which  dissolves  off  all  the  remaining  sen- 
sitive coating.  The  plate  is  protected  to  some  extent  from  mechanical  in- 
jury, and  a  richer  and  warmer  effect  given  to  the  picture,  by  covering  it  with 
a  very  delicate  film  of  reduced  gold.  This  is  accomplished  by  dipping  the  plate 
into  a  solution  of  chloride  of  gold,  and  heating  it  over  the  flame  of  a  spirit- 
lamp. 

The  surface  of  the  plate  is  rendered  uneven  by  the  operation  of  light  upon 
it,  so  that  it  admits  of  being  copied  by  the  process  of  electrotyping. 

663.  Paper    Photographs  , — The  plan  of  obtaining  permanent  pho- 
tographic images  upon  paper  was  originally  devised  by  Mr.  Talbot  of  En- 
gland in    1839.     The  process  first  followed  consisted  in  soaking   ordinary 
writing-paper  in  a  weak  solution  of  common  salt,  and  when  dry  washing  it 
over  on  one  side  with  a  solution  of  nitrate  of  silver.     This  operation  was 
performed  by  candle-light,  and  the  paper  dried  by  a  fire.     The  sheet  thus 
prepared,  when  laid  under  an    engraving  or  leaf,  arid  exposed  to  diffused 
daylight  for  a  period  of  about  half  an  hour,  receives  a  fair  impression,  with 
the  lights  and  shadows  reversed.      The  picture  thus  formed  is  preserved 
from  further  change  by  immersing  it  in  a  solution  of  salt. 

664.  Talbotype  , — In  1841,  Mr.  Talbot  invented  the  process  known  as 
the  Talbotype,  or  Calotype,  which  is  essentially  the  plan  at  present  followed 
in  obtaining  photographs  on  paper  by  the  camera.     The  paper  (smooth  writ- 
ing-paper) is  first  brushed  over  with  a  solution  of  nitrate  of  silver,  and  then 
immersed  in  a  bath  of  iodide  of  potassium.     In  this  way  a  surface  of  iodide 
of  silver  upon  paper  is  prepared,  which   is  not  of  itself  sensitive  to  the  ac- 
tion of  light.     These  operations  may  be  conducted  in  diffused  daylight,  and 
a  stock  of  paper  may  be^  prepared  at  once  and  kept  for  use.     In  order  to 
render  the  paper  sensitive  to  the  action  of  light,    it  is  washed  over  with  a 
mixture  of  nitrate  of  silver  with  gallic  and  acetic  acids,  and  then  exposed 
in  the  camera.     Unless  the  light  is  very  strong,  the  paper  when  withdrawn 
exhibits  no  image,  or  a  mere  outline,  but  the  compound  has  undergone  a 
very  remarkable  change ;  for  if  the  blank  sheet  be  washed  over  with  the 
mixture  of  nitrate  of  silver  with  gallic  and  acetic  acids,  and  then  gently 
warmed,  an  image  appears  with  wonderful  distinctness  and  .fidelity,  the  por- 
tions exposed  to  the  strongest  lights  assuming  the  darkest  tints.     The  de- 
velopment of  the  image  in  this  process   appears  to  be  due  to  the  reducing 
agency  of  the  gallic  acid,  which  acts  more  rapidly  upon  those  portions  of  the 
surface  which  have  been  most  freely  exposed  to  the  action  of  light.     The  dor- 
mant picture  may  be  developed  many  hours,  or  even  days  after  it  has  been 
produced,  provided  the  paper  be  kept  in  the  dark.     It  seems  as  though  the 
light,  without  actually  producing  a  decomposition  of  the  particles  of  the  sil- 
ver salt  upon  which  it  falls,  gives  to  them  a  peculiar  condition  of  unstable 
equilibrium,  which  predisposes  to  decomposition  when  acted  upon  by  a  re- 

QTTESTIONB. — What  was  the  original  process  for  obtaining  paper  photographs  ?     Describe 
the  Talbotype. 


400  INORGANIC    CHEMISTRY, 

during  agent  like  gallic  acid.  The  picture  la  preserved  in  this  instance,  as 
in  most  others,  from  future  change,  by  dissolving  off  the  exciting  agents  by 
solutions  of  the  hyposulphites, — MILLER, 

As  silver  tablets  are  expensive,  and  paper  somewhat  unreliable,  glass 
coated  with  a  sensitive  substance  has  been  extensively  introduced  as  a  ma- 
terial for  receiving  the  photographic  images,  Glass  ia  chiefly  prepared  for 
this  purpose  in  two  ways ;  by  coating  it  with  a  thin  film  of  albumen  containing 
iodide  of  potassium  (the  albumen  process) ;  or  by  coating  it  with  collodion,  con- 
taining iodide  of  potassium  (the  collodion  process).*  The  surfaces  thus  formed, 
when  dried  and  washed  with  a  compound  of  silver,  are  ready  for  exposure 
in  the  camera.  The  collodion  film  can  be  rendered  so  sensitive  to  light,  that 
a  perfect  picture  can  be  formed  upon  it  by  an  exposure  continuing  for  less 
than  one  second  of  time.  In  what  are  called  ambrotypes,  the  picture  is  first 
formed  upon  a  film  of  collodion  and  then  varnished  with  a  solution  of  bal- 
sam, which  is  thought  to  render  the  image  more  distinct. 

Although  the  agents  indicated  are  the  ones  chiefly  employed  in  phot- 
ography, recent  researches  have  shown  that  nature  abounds  in  materials  sus- 
ceptible of  photographic  action.  Preparations  of  gold,  platinum,  mercury, 
iron,  copper,  tin,  nickel,  manganese,  lead,  potash,  etc.,  have  been  found  more 
or  less  sensitive,  and  capable  of  producing  pictures  of  beauty  and  distinctive 
character.  The  juices  of  many  plants  and  flowers  have  also  been  put  into 
requisition,  and.  papers  impregnated  with  them  have  been  made  to  receive 
delicate,  though  in  most  cases,  fugitive  images.f  Attempts  have  also  been 
made,  with  a  considerable  degree  of  success,  to  cause  the  light  not  only  to 
draw,  but  also  to  engrave  the  image  upon  a  prepared  basis,  in  such  a  way 
that  the  surface  may  be  used  for  printing. 

665.  Photographs  in  Colors. — All  attempts  to  produce  photo- 
graphs in  their  natural  colors  have  as  yet  been,  on  the  whole,  unsuccessful, 
although  a  partial  success  has,  in  some  instances,  been  attained  to.  The  cir- 
cumstance that  the  rays  by  which  photographic  effects  are  produced  are  dark 
rays,  entirely  distinct  from  the  rays  constituting  color,  would  appear,  a,  priori, 
unfavorable  to  a  successful  result.  .. 


*  Albumen  is  prepared  for  this  purpose  by  beating  up  the  white  of  eggs  with  iodide  of 
potassium.  Collodion  mixture  is  formed  by  dissolving  gun-cotton  in  ether,  and  adding 
iodide  of  potassium. 

t  The  terms  which  have  been  applied  to  designate  the  effects  resulting  from  the  use  of 
various  materials  are  very  numerous.  Thus  we  hare  the  Chrysotype,  in  which  Salts  of 
iron  and  gold  are  used ;  Cyanotype,  in  which  impressions  are  produced  by  salts  of  iron,  in 
conjunction  with  those  of  cyanogen;  Anthotijpe,  in  Which  juices  of  the  poppy,  rose,  etc., 
are  employed,  and  many  others. 

QUESTIONS.— What  materials  have  been  substituted  as  a  basis  for  photographic  action  in 
place  of  silver  and  glass?  What  are  the  albumen  and  collodion  processes?  What  is  an 
ambrotype  ?  Is  photographic  action  restricted  to  a  fetr  substances?  Illustrate  this  fact. 
What  is  said  of  photographs  in  colors  ? 


T  U  ° 


ORGANIC   CHEMISTRY. 


ORGANIC  Chemistry  is  that  department  of  science  which 
treats  of  the  chemical  nature  and  relations  of  those  sub- 
stances which  are  derived,  either  directly  or  indirectly, 
from  organized  beings, — animal  or  vegetable. 

£  ( 


CHAPTER   XVI. 


NATURE     OF     ORGANIC     BODIES. 

666.  Composition  of  Organic  Substances, — The  number 
of  elements  which  enter  into  the  composition  of  organic  substances  is  ex- 
tremely limited,  the  great  bulk  of  all  of  them  being  made  up  of  carbon,  hydro- 
gen, oxygen,  and  nitrogen,  with  which  are  generally  associited  extremely 
small  quantities  of  sulphur,  phosphorus,  iron,  and  a  few  other  elements.  The 
infinite  differences  of  appearance  and  properties  which  organic  substances 
manifest,  is  due  either  to  a  variation  in  the  number  of  the  combining  atoms 
of  their  constituent  elements,  or  to  a  variation  in  the  grouping  or  arrangement 
of  the  constituent  atoms  as  respects  each  other. 

Thus,  for  example,  vinegar  differs  from  alcohol  only  in  containing  a  little 
more  oxygen  and  a  little  less  hydrogen,  while  the  proportion  of  carbon  is  the 
same  in  both ;  the  change  of  properties,  which  is  occasioned  by  this  slight 
change  in  compostion,  is,  however,  exceedingly  great ;  on  the  other  hand,  the 
most  careful  chemical  analysis  reveals  no  difference  in  the  composition  of 
woody-fiber,  starch,  and  gum,  each  consisting  of  precisely  the  same  elements 
united  in  the  same  proportions.  The  difference  in  properties  in  this  case,  is 
supposed  to  be  due  to  a  difference  in  the  grouping  of  the  atoms,  somewhat 
as  is  represented  in  Figs.  205,  206,  207. 


QUESTIONS.— What  is  organic  chemistry  ?  What  is  said  of  the  composition  of  organic 
compounds  ?  How  are  so  many  different  organic  compounds  produced  from  so  few  ele- 
ments ?  Illustrate  this. 


402 


ORGANIC     CHEMISTRY. 


The  number  of  such  isomeric  bodies  in  organic  chemistry  is  very  large, 
while  their  occurrence  in  inorganic  chemistry  is  extremely  rare. 


FlG.  205. 

WOODY   FIBER. 


By  far  the  largest  proportion  of  the  substances  which  make  up  the  struc- 
ture of  plants  are  composed  of  but  three  elements — carbon,  hydrogen,  and 
oxygen.  Animal  substances,  on  the  contrary,  are  generally  characterized  by 
the  presence  of  nitrogen.  Bodies  which  contain  nitrogen  are  designated  as 
azotized  compounds ;  and  those  which  are  wanting  in  it,  as  non-azotized  com- 
pounds. 

667.  The  elements  of  organic  bodies,  in  uniting  with  each  other,  are  gov- 
erned by  the  same  laws  of  combination  which  regulate  the  composition  of 
mineral  or  inorganic  substances.  The  manner,  however,  in  which  the  atoms 
of  the  constituent  elements  are  associated  in  the  one  class  of  compounds  is, 
in  general,  altogether  different  from  what  it  is  in  the  other — inorganic  com- 
pounds being  characterized,  for  the  most  part,  by  a  great  simplicity  of  compo- 
sition, while  those  of  organic  origin  are  remarkable  for  their  very  great  com- 
plexity. Thus  water,  HO,  is  composed  of  1  atom  or  equivalent  of  hydrogen, 
and  1  of  oxygen,-  Sulphuric  acid,  80s,  of  1  of  sulphur  and  3  of  oxygen;  hy- 
drochloric acid,  HC1,  of  1  of  hydrogen  and  1  of  chlorine,  etc.  On  the  other 
hand,  alcohol  consists  of  4  atoms,  or  equivalents,  of  carbon,  6  of  hydrogen, 
and  2  of  oxygen,  its  composition  being  represented  by  the  formula  CJIeOj; 
and  ordinary  sugar,  of  12  atoms  of  carbon,  11  of  hydrogen,  and  11  of  oxygen, 
or  CiaHnOii.  The  composition  of  stearic  acid,  the  basis  of  stearine,  is  also 
represented  by  the  formula  C68H66Os,  and  that  of  fibrine,  the  principal  con- 
stituent of  muscular  fiber,  by  C^HsioNsoOiooPS. 

As  a  consequence  of  this  complexity  of  composition,  organic  substances  are, 
as  a  class,  far  more  unstable  and  more  liable  to  decomposition  from  slight 
causes  than  inorganic  substances; — the  power  to  resist  the  action  of  disturb- 
ing forces  decreasing,  as  a  general  rule,  as  the  number  of  combined  atoms  or 
equivalents  increases.  It  is  also  a  noticeable  fact  that  all  those  organic 

QUESTIONS. — What  organic  bodies,  as  a  class,  are  generally  wanting  in  nitrogen? 
What  generally  contain  it?  In  what  manner  do  the  elements  of  compound  bodiea  unite 
with  each  other  ?  What  are  characteristics  of  the  composition  of  organic  and  inorganic 
bodies?  Illustrate  this.  What  is  the  consequence  of  the  complexity  of  the  composition 
of  organic  bodies  ?  What  is  a  noticeable  fact  in  relation  to  organic  compounds  of  a  high 
order? 


NATURE     OF     ORGANIC     BODIES.  403 

bodies  which  discharge  high  organic  functions,  as  the  substance  of  the  brain, 
the  nerves,  and  the  blood,  have  a  most  wonderfully  complex  constitution,  and 
are  susceptible  of  disorganization  from  the  slightest  causes.* 

"When  organic  substances  are  decomposed  by  the  action  of  heat,  light,  elec- 
tricity, chemical  affinity,  and  even  by  mechanical  action,  they  do  not  tend  to 
divide  into  separate  and  isolated  elements,  but  to  form  more  simple  com- 
pounds. Thus  1  (compound)  atom  of  grape  sugar,  CnHuOu,  easily  divides 
in  2  atoms  of  alcohol,  2(C4H602),  4  of  carbonic  acid,  and  2  of  water.  If  an  or- 
ganic body  be  exposed  to  an  intense  degree  of  heat,  with  access  of  air,  its 
constituents  all  unite  with  oxygen  to  form  gaseous  compounds,  and  it  is  com- 
pletely consumed — generally  after  it  has  been  converted  into  a  black,  carbon- 
aceous mass.  The  property  of  blackening  when  a  body  is  exposed  to  heat, 
which  is  due  to  the  presence  of  carbon,  is  a  sure  characteristic  of  its  organic 
derivation. 

668.  Origin  of  Organic  Substances,— Organic  sub- 
stances have  their  origin  entirely  in  plants. 

The  chemist,  when  he  exerts  his  skill  on  materials  of  an  organic  origin, 
extracts  a  series  of  substances,  each  proceeding  from  the  other,  whose  com- 
position becomes  more  and  more  simple,  until  it  reaches  some  species  known 
to  mineral  chemistry.  Thus,  from  sugar  we  may  extract  alcohol  and  car- 
bonic acid,  and  from  alcohol  water  and  bi-carbureted  hydrogen.  In  the 
vegetable  organization,  on  the  other  hand,  an  operation  exactly  the  reverse 
takes  place.  The  living  structure  takes  in  air,  water,  and  mineral  elements, 
assimilates  them,  and  in  virtue  of  a  certain  peculiar  force,  builds  them  up  and 
disposes  them  into  groups  of  a  certain  stability — or  into  organic  products. 


*  "  There  is  a  physical  character  which  will  sometimes  enable  us  to  give  a  good  guess 
as  to  the  simple  or  complex  constitution  of  an  organic  substance — the  faculty  of  crystalli- 
zation. The  power  of  assuming,  on  solidification,  a  distinct  and  often  very  characteristic 
geometrical  form,  appears  to  be  possessed  by  all  chemical  compounds  of  a  definite  and 
constant  composition,  with  the  exception  of  a  certain  number,  principally  to  be  found  in 
a  class  of  organic  substances  of  the  most  complicated  and  unstable  nature.  We  know 
nothing,  and  apparently  at  present  can  know  nothing,  of  the  ultimate  structure  of  any 
substance  whatever  ;  but  it  is  not  difficult  to  figure  to  one's  self  some  idea  of  the  gradual 
weakening  of  the  molecular  forces  upon  which  crystallization  depends,  whatever  the  na- 
ture of  those  forces  may  be,  by  an  increase  in  their  number,  and  in  the  multiplicity  of 
directions  in  which  the  forces  themselves  are  exerted.  It  very  often  happens  that  in  those 
cases  where  crystalline  texture  is  altogether  absent,  we  observe  in  its  place  an  appearance 
of  a  very  different  kind  ;— we  notice  that  the  smallest  particles  of  matter  which  can  be 
traced  by  the  microscope  exhibit  a  rounded  or  globular  figure  instead  of  the  straight  lines 
and  angles  of  the  crystallizable  compounds.  These  very  frequently  appear  to  aggregate 
together  in  strings,  or  rows,  not  altogether  unlike  some  of  the  very  lowest  structures  of 
the  vegetable  world,  where  a  commencement  of  organization  is,  as  it  were,  just  visible. 
The  substances  forming  the  chief  constituents  of  the  animal  body  are  in  this  condition." 
— Actonian  Prize  Essay,  Fownes. 

QUESTIONS. — What  circumstances  attend  the  decomposition  of  organic  bodies  ?  What 
property  indicates  the  derivation  of  an  organic  substance  ?  What  is  the  primal  origin  of 
all  organic  substances  ?  Illustrate  this.  Do  animal  structures  create  organic  products  ? 


404  ORGANIC    CHEMISTRY. 

The  force  by  which  this  result  is  brought  about  is  called  the  vital  or  life  force ; 
but  we  know  nothing  of  its  nature,  and  recognize  it  simply  by  its  effects. 

Organic  substances  thus  originated  pass  into  the  systems  of  animals,  which 
possess  no  power  of  creating  or  forming  the  materials  which  compose  their 
structures,  and  can  only  consume  and  transform  that  which  is  supplied  to  them 
by  plants. 

Man  has  never  yet  been  able  to  artificially  make  an  organic  body ;  by 
which  assertion  we  mean  to  be  understood,  that  he  has  never  been  able  to 
take  the  single  or  dead  elements,  and  cause  them  to  unite  at  will  so  as  to 
form  compounds  like  those  produced  through  the  agency  of  animal  or  vege- 
table life.  Chemists  are,  however,  able  to  transform  one  organic  body  into 
another,  or  to  unite  materials  derived  from  substances  already  organized  into 
compounds  possessing  characters  entirely  different  from  those  of  their  con- 
stituents. Thus,  starch  may  be  transformed  into  sugar,  and  sugar  into  the 
acid  of  ants  (formic  acid) ;  some  of  the  essential  oils  have  also  been  produced 
artificially,  and  within  the  last  few  years  (1855),  Bertholet,  an  eminent  French 
chemist,  has  succeeded  in  making  alcohol  from  sulphuric  acid,  water,  and  bi- 
carburetted  hydrogen.* 

669.  Compound  Radical  s.— It  has  been  already  shown  that  cyano- 
gen and  ammonium,  compound  bodies,  comport  themselves  in  every  respect 
like  radicals,  or  elements.  In  organic  chemistry  many  such  compound  radi- 
cals are  recognized,  some  consisting  of  two  elements,  carbon  and  hydrogen, 
and  some  of  three  or  four,  carbon,  hydrogen,  oxygen,  and  nitrogen.  Some, 
like  cyanogen,  correspond  in  properties  to  the '  metalloids ;  others,  like  ammo- 
nium, resemble  the  metals,  and  both  by  uniting  with  oxygen,  chlorine,  and 
acids,  form  oxyds,  chlorides,  and  salts.  Each,  also,  by  the  addition  or  group- 
ing round  it  of  other  molecules,  constitutes  the  root  or  basis  of  a  whole  class 
or  series  of  compounds. 

Thus,  for  example,  carbon  unites  to  hydrogen  in  the  proportion  of  4  atoms 
of  the  former  to  5  of  the  latter,  CiHs,  to  fgrm  a  radical  called  Ethyle.  Ethyle 
oxydated,  forms  oxyd  of  ethyle,  or  ether,  C4"E5-(-0 ;  oxyd  of  ethyle  plus  an 
atom  of  water,  forms  hydrated  oxyd  of  ethyle,  C4lI5,0,HO,  or  alcohol,  the 
formula  of  which  is  generally  written  C^IeOs ;  ethyle,  plus  an  atom  of  chlo- 
rine, forms  chloride  of  ethyle,  C4H5,C1,  and  if  sulphur  be  substituted  in  the 
place  of  chlorine,  we  have  sulphide  of  ethyle,  C4H5}S;  and  in  this  way,  by 


*  The  muscles  of  animals  and  the  fiber  of  wood  consist  of  distinct  chemical  compounds, 
•which  the  chemist  has  been  able  to  isolate  and  study,  but  not  to  imitate.  It  is  hoped,  and 
expected  by  some,  that  the  power  will  ultimately  be  attained  to  of  artificially  forming 
those  products  which,  in  the  form  of  meat,  cotton,  flax,  etc.,  are  so  essential  to  the  wel- 
fare of  man.  The  advocates  of  the  possibility  of  such  a  result  find  some  support  of  their 
views  in  the  fact  that  two  organic  bodies,  cyanogen  and  ammonia,  are  undoubtedly  formed 
artificially  in  the  workings  of  blast-furnaces,  but  in  what  manner  it  is  impossible  at 
present  to  explain. 

QtTESTTONB.— Can  we  artificially  accomplish  this  ?  What  power  do  we  possess  ?  What 
are  compound  radicals?  What  is  the  character  of  the  radicals  recognized  in  organic 
chemistry  ?  Illustrate  how  classes  of  compounds  are  formed  from  such  a  basis  ? 


VEGETABLE    TISSUE.  405 

the  continued  addition  or  subtraction  of  elements,  a  great  variety  of  compound 
bodies  may  be  formed,  all  referable  to  one  central  radical.  Ethyle  itself  may 
be  also  obtained  from  its  oxyd,  as  potassium  is  derivable  from  oxyd  of  po- 
tassium, or  potassa,  although  by  a  different  process. 

The  discovery  and  recognition  of  these  compound  radicals  has  greatly 
facilitated  the  progress  of  organic  chemistry,  and  has  rendered  it  possible  to 
classify  and  arrange  in  groups  a  great  number  of  bodies,  which  from  their  di- 
verse properties  would  seem  to  have  no  connection  with  each  other.  Thus, 
the  fats,  the  oils,  the  resins,  the  alcohols,  the  ethers,  with  many  coloring, 
odoriferous,  and  medicinal  substances,  are  now  grouped  and  studied  as  de- 
rivatives from  various  central  radicals,  and  not  as  independent  principles. 
There  are,  however,  many  organic  substances  of  great  importance,  the  radi- 
cals of  which  have  not  yet  been  discovered. 


CHAPTER    XVII, 

ESSENTIAL  IMMEDIATE   PRINCIPLES    OF   PLANTS. 

670.  BY  the  essential  immediate  principles  of  plants,  we  understand  those 
substances  which  the  plant  appears  to  form,  through  the  agency  of  the  vital 
force,  directly  from  the  inorganic  elements  obtained  from  without ;  or  those 
principles  which  mainly  constitute  the  structure,  in  a  greater  or  less  degree, 
of  all  plants,  and  are  essential  to  then*  existence. 

These  substances  are  also  often  spoken  of  as  the  proximate  principles  of 
plants,  and  are  conveniently  divided  into  two  classes,  viz.,  those  which  con- 
tain nitrogen,  as  albumen,  gluten,  vegetable  casein,  etc.,  and  those  which  are 
destitute  of  this  element,  as  vegetable  tissue  (woody-fiber),  starch,  gum,  sugar, 
etc.  The  separation  of  an  organized  substance"  into  its  proximate  substances, 
or  principles,  is  called  its  proximate  analysis ;  and  its  separation  into  its  final 
or  simple  elements,  its  ultimate  analysis. 

In  the  consideration  of  the  two  classes  of  the  proximate  principles  of 
plants,  it  is  most  convenient  to  commence  with  those  which  do  not  contain 
nitrogen  as  a  constituent  element. 

SECTION    I. 

VEGETABLE    TISSUE,     STARCH,     GUM,     SUGAR,     ETC. 

671,  Organic    Structure . — Since  the  discovery  of  the  microscope, ' 
unwearied  efforts  have  been  made  to  ascertain  the  manner  in  which  dead 
and  inert  inorganic  elements  unite  to  form  organized  and 'living  structures. 

QtrESTioNS. — What  do  we  understand  by  the  essential  immediate  principles  of  plants  ? 
Into  what  two  classes  are  the  proximate  principles  of  plants  divided  ?  What  is  under- 
stood by  a  proximate  and  an  ultimate  analysis  ? 


406 


ORGANIC     CHEMISTRY. 


FIG.  208. 


FIG.  209. 


The  result  of  all  inquiries  have  terminated  in  the  establish- 
ment of-  a  single  fact,  viz.,  that  the  lowest  primary  form 
of  organization  we  can  detect,  whether  of  the  individual 
(animal  or  vegetable)  or  of  its  parts,  is  a  cell — a  little  glob- 
ular or  oval  body,  membranous  or  solid  externally,  fluid 
within.  (See  Figs.  208,  209,  210.)  Beyond  this  we  can 
not  go,  or  say  how  it  is  that  the  elementary  particles  of 
matter  are  led  to  assume  this  form ;  but  the  appearance 
of  cells  always  precedes  the  formation  of  circulating  ves- 
sels, or  any  of  the  more  complex  forms  of  organic  struc- 
ture. 

Cells  once  formed,  multiply  in  number  by  division  (see 
Figs.  209,  210),  and  by  the  introduction  of  new  matter 
from  without,  and  thus  it  is  that  all  growth,  or  increase  in 
volume  and  weight,  in  -all  animals  and  vegetables,  takes 
place ;  and  an  animal  or  plant  is  a  structure  "  built  up 

of  individual  cells, 

.  211.  somewhat      as      a 

house  is  built  of 
bricks."  Fig.  211 
represents  a  mag- 
nified view  of  the 
cellular  tissue  of  a 
rootlet. 

672.  The  natural 
figure  of  a  cell  is 
globular,  but  under 
varying  circum- 
stances it  may  as- 
sume a  great  variety 
of  forms.  The  hairs  on  the  surface  of  plants  are  cells  drawn  out  into  tubes,  or 
are  composed  of  continuous  rows  of  cells.  Cotton  consists  of  simple  long 
hairs  on  the  coat  of  the  seed ;  and  each  of  these  hairs  is  a  single  cell.  Fig. 
212  is  a  microscopic  appearance  of  a  section  of  the  stalk  of  the  calla,  showing 
the  arrangement  of  the  cells,  with  passages  between  them.* 


FIG.  210. 


*  The  size  of  the  common  cells  of  plants  varies  from  about  the  thirtieth  to  the  thou- 
sandth of  an  inch  in  diameter.  An  ordinary  size  is  from  l-300th  to  l-500th  of  an  inch  in 
diameter ;  so  that  there  may  be  generally  from  27  to  125  millions  of  cells  in*  the  compass 
of  a  cubic  inch.  Now  when  it  is  remembered  that  many  stems  of  plants  shoot  up  at 
the  rate  of  an  inch  or  two  a  day,  and  sometimes  of  three  or  four  inches,  we  may  form 
some  conception  of  the  rapidity  of  their  formation.  When  a  portion  of  any  young  and 
tender  vegetable  tissue,  such  as  an  asparagus  root,  is  boiled,  the  elementary  cells  sepa- 
rate, or  may  be  readily  separated  by  the  aid  of  fine  needles,  and  examined  by  the  micro- 
scope.— GEAY. 

QUESTIONS. — In  what  form  does  organization  first  manifest  itself?  What  is  a  cell? 
How  do  plants  and  animals  grow  and  increase  ?  What  is  the  natural  figure  of  cells  ? 


VEGETABLE     TISSUE.  407 

673.  A  living  cell  possesses  a  wonderful  power  of  influencing  chemical 
action ;  and  what  is  called  "  secretion"  in  animals  and  plants  is  the  result 
of  the  exercise  of  this  function.  By  means  of  it,  the  cell  first  draws  in  or 
secretes  inorganic  matter,  and  then  organizes  it,  or  fits  it  into  its  own  struc- 
ture. Different  cells  manifest  very  different  powers ;  for  example,  one  kind 
of  cell  will  decompose  carbonic  acid,  reject  the  oxygen,  and  preserve  the  car- 

FiG.  212. 


bon  within  its  walls  or  tissues ;  another  will  produce  out  of  the  inorganic  con- 
stituents of  the  air  the  odoriferous  principle  of  the  rose ;  a  third  will  convert 
a  portion  of  blood  into  milk  ;  and  yet  to  the  eye  they  are  all  alike,  "  a  collec- 
tion of  little  wet  bladders." 

674.  Cellulose,  or  Cellular  Tissue,  Ci2HioOi0. — The  mate- 
rials of  which  the  walls  of  the  cells  of  plants  is  composed  is  termed  in  chem- 
istry cellulose,  or  cellular  tissue.  It  consists  of  three  elements,  carbon,  hydrogen, 
and  oxygen,  and  has  the  same  composition,  when  pure,  in  all  plants.  It  is 
distinguished  among  all  the  substances  which  enter  into  the  composition  of 
plants  by  its  great  resistance  to  chemical  agents — a  resistance  which  allows 
its  separation  in  a  state  of  purity. 

Cellulose  is  nearly  pure  hi  cotton,  and  in  the  fibers  of  the  flax  and  hemp- 
plants,  also  in  paper  and  old  linen  and  cotton  cloth.  The  difference  between 
cotton  and  flax  is  due  simply  to  a  difference  in  the  mechanical  construction  of 
their  fibers ;  the  fiber  of  cotton  being  a  flattened  tube  or  hollow  ribbon  with- 
out joints,  and  with  pointed  or  rounded  ends ;  while  the  fibers  of  flax  and 
hemp  consist  of  rounded  tubes  (cells)  bundled  or  jointed  together  in  parallel 
directions,  and  easily  separable  into  shorter  and  more  minute  filaments. 
Cotton  fibers  have  what  is  called  a  staple  ;  that  is,  they  are  all  of  the  same 
length,  and  are,  therefore,  easily  spun  by  machinery ;  flax  and  hemp  fibers 
are,  on  the  contrary,  irregular  in  length,  and  are  more  rigid  than  cotton,  and 
can  not  be  so  easily  twisted  into  fine,  regular  threads.  Fig.  213  represents 
the  microscopic  appearance  of  cotton,  and  Fig.  214  that  of  flax. 

Cellulose  is  insoluble  in  water,  alcohol,  ether,  and  dilute  acids.     By  treat- 

QUESTIONS — What  property  do  cells  possess?  Illustrate  this.  What  is  cellulose? 
By  what  other  name  is  it  known  ?  In  what  substances  is  it  nearly  pure  ?  What  consti- 
tutes the  difference  between  flax  and  cotton  ?  What  is  meant  by  the  staple  of  cotton  ? 
What  are  the  properties  of  cellulose  ? 


408 


ORGANIC     CHEMISTBY. 


214. 


ing  sawdust  successively  with  warm  water,  alcohol,  ether,  alkalies  and  acids, 

FIG.  213.  we  may  remove  from   the 

wood  all  its  soluble  constitu- 

ents, and  obtain  cellulose  in 

a  pure  condition.    By  con- 

tinued contact  with  chlorine, 

acids,  and  alkalies,  cellulose 

is,  however,  gradually  de- 

composed and  destroyed. 
675.    Gun-cotton, 

Pyroxyline.  —  When  cellu- 

lose is  subjected  to  the  ac- 

tion of  nitric  acid,  or  to  a 

mixture  of  nitric  and  sul- 

phuric acids,  it  gives  up  a 

portion  of  its  hydrogen  and 
oxygen  (as  water),  and  receives  nitric  acid  in  place  —  becoming  transformed 
thereby,  without  change  of  physical  appearance,  into  an  explosive  substance 
which  is  known  as  gun-cotton,  or  pyroxylins. 

The  process  by  which  gun-cotton  is  formed  is  essentially  as  follows  :  per- 
fectly clean  cotton  is  soaked  for  about  five  minutes  in  a  mixture  composed 
of  1  part  concentrated  nitric  acid,  with  2  parts  concentrated  sulphuric  acid  ; 
it  is  then  removed,  carefully  washed  with  water  from  every  trace  of  acid, 
and  dried  by  exposure  to  the  air.  As  thus  prepared,  it  retains  the  appear- 
ance of  cotton,  but  inflames  instantaneously  when  touched  with  a  hot  wire  or 
lighted  match,  and  when  struck  with  a  hammer  upon  an  anvil,  explodes 
with  great  violence.  When  used  in  fire-arms,  it  acts  like  gunpowder,  but  its 
explosive  force  is  at  least  four  times  greater  than  that  of  powder,  and  it  does 
not,  moreover,  foul  the  gun  to  the  same  extent  as  the  latter  substance.  Its 
liability  to  burst  the  gun  and  to  accidental  explosions  has,  however,  caused 
its  rejection  for  most  .  practical  purposes,  and  in  experimenting  with  it  too 
great  caution  can  not  be  exercised.  By  subjecting  starch  and  sugar  to  treat- 
ment with  nitric  acid,  other  explosive  substances  analogous  to  gun-cotton 
may  be  formed. 

676.  Collodion  ,  —  Gun-cotton  is  insoluble  in  both  water  and  alcohol  ; 
it  dissolves  sparingly  in  pure  ether,  but  readily  hi  ether  containing  a  small 
percentage  of  alcohol     Its  ethereal  solution  constitutes  a  syrupy  liquid  which 
yields  by  evaporation  a  thin,  transparent,  powerfully  adhesive  substance,  in- 
soluble in  water.     This  product,  which  has  received  the  name  of  collodion, 
is  advantageously  used  as  a  substitute  for  court-plaster  for  the  covering  of 
wounds,  and  also  as  a  sensitive  basis  for  the  reception  of  photographic  pictures. 

677.  Parchment    Pape  r,  —  When  paper  is  exposed  to  a  mixture  of 


QUESTIONS.— What  is  the  action  of  nitric  acid  upon  cellulose  ?  What  is  the  process  of 
making  gun-cotton  ?  What  are  its  properties  ?  What  is  collodion  ?  What  action  does 
sulphuric  acid  have  upon  paper  ? 


VEGETABLE     TISSUE.  409 

2  parts  concentrated  sulphuric  acid  (s.g.,  T854,  or  thereabouts)  with  1  of  water, 
for  no  longer  time  than  is  taken  in  drawing  it  through  the  acid,  it  is  imme- 
diately converted  into  a  strong,  tough,  skin-like  material,  to  which  the  name 
"  parchment  paper1'1  has  been  applied.  All  traces  of  the  sulphuric  acid  must 
instantly  be  removed  by  washing.  If  the  strength  of  the  acid  much  exceeds 
or  falls  short  of  the  limits  named,  the  paper  is  eitlier  charred  or  transformed 
into  other  compounds.  By  this  treatment,  in  a  little  more  than  a  second  of 
time  a  piece  of  feeble,  porous,  unsized  paper  is  rendered  so  strong,  that  a 
ring  seven  eighths  of  an  inch  in  width  is  said  to  be  capable  of  sustaining  a 
weight  of  90  Ibs.  The  nature  of  the  change  thus  effected  is  not  understood, 
the  chemical  composition  and  weight  of  the  paper  remaining  unaltered.  It 
is,  however,  somewhat  contracted  in  dimensions,  is  not  affected  by  water  like 
common  paper,  and  is  not  decomposed  by  heat  and  moisture  like  common 
parchment. 

678.  L  i  g  n  i  n  e  • — As  the  growth  of  the  plant  continues,  the  walls  of  the 
cells  constituting  the  cellular  tissue  generally  become  incrusted  on  their  in- 
terior surfaces  with  a  substance  formed  from  the  organic  matters  dissolved 
in  the  sap.     This  substance  constitutes  the  principal  part  of  the  weight  of 
wood  (lignum),  and  is  chemically  known  as  lignine.     It  grows  thicker  with 
the  age  of  the  plant,  and  finally  fills  up  the  cells,  FIG.  215. 
leaving,  however,  minute  pores  or  conduits  for  the 

circulation  of  the  sap.  Fig.  215  represents  a  mi- 
croscopic section  of  wood-cells  of  the  birch,  nearly 
filled  up  by  regular  depositions  of  lignine.  The 
difference  between  the  heart- wood  and  sap-wood, 
or  external  wood,  of  a  tree,  is  due  simply  to  the 
fact,  that  the  cells  of  the  center  are  the  oldest,  and 
consequently  are  more  densely  and  compactly  filled  j 
with  ligneous  matter  than  those  which  have  beea 
formed  later,  and  constitute  the  exterior  of  the  tree. 
It  is  by  this  thickening  of  the  cells  that  the  skins 
of  fruits  and  the  shells  of  nuts  acquire  their  hard- 
ness, and  it  is  simply  through  variations  in  the  continuance  of  this  process, 
'and  in  the  nature  of  the  materials  deposited,  that  all  the  different  appearances 
of  wood  originate ;  the  coloring  and  resinous  matters  of  wood  being  deposited 
in  connection  with  the  lignine. 

Lignine  can  not  be  isolated  in  a  state  of  purity ;  it  is  supposed  to  dif- 
fer somewhat  from  cellulose,  or  the  original  cell -membrane,  in  containing  a 
little  more  hydrogen  and  carbon ;  it  is,  therefore,  richer  in  combustible  mat- 
ter. 

679.  Destructive  Distillation  of  Wood  , — When  wood  is  sub- 
jected to  heat  in  close  vessels  (distillation),  or  with  a  partial  access  of  air,  a  great 

QUESTIONS. — Describe  the  process  for  preparing  parchment  paper.  What  is  lignine? 
"What  constitutes  the  difference  between  the  heart-wood  and  sap-wood  of  a  tree  ?  What 
are  other  illustrations  of  the  formation  of  lignine  ?  What  is  fcAid  of  the  chemical  compo- 
sition of  lignine  ? 


410  ORGANIC    CHEMISTRY 

variety  of  products  are  obtained,  which  aro  characterized  by  singularly  differ- 
ent properties.  The  principal  of  these  aro  charcoal,  which  is  riot  volatile, 
and  remains  behind,  illuminating  gas  (carburets  of  hydrogen),  carbonic  acid, 
water,  pyroligneous  acid,  and  a  resinous  substance  known  as  "  wood-tar.1' 
Of  th.se  several  substances,  the  two  last  mentioned  only  remain,  unconsid- 
ered ;  they  are  extensively  used  in  the  arts,  and  are  obtained  upon  a  largo 
scale  by  distilling  wood  in  iron  cylinders. 

680.  Pyroligneous    Acid,  sometimes  called  wood  vinegar,  is  a  brown 
acid  liquid,  having  a  strong  smoky  taste  and  flavor.     It  is  obtained  most 
abundantly  by  the  distillation  of  dry  beach-wood — a  pound  of  wood  yielding 
nearly  one  half  pound  of  acid.     Its  uses  and  chemical  composition  will  be 
hereafter  noticed. 

681.  Creosote    is   a   colorless,  oily  fluid,  obtained   from   pyroligneous 
acid  and  wood-tar.     It  possesses  a  peculiar  penetraiing  odor  of  smoke,  and 
when  applied   to   the  skin   of  the   mouth   or   tongue,   acts   as  a  cautery. 
Creosote  is  one  of  the  most  powerful  antiseptic  agents  known  in  chemistry. 
Hence  the  etymology  of  its  name,  from  the  Greek  /c/>ewr,  ftesli,  and  CTW^W,  I 
preserve.     Meat  steeped  for  about  24  hours  in  a  solution  of  1  part  of  creosote 
to  100  of  water,  is  rendered  incapable  of  putrefaction,  and  acquires  a  delicate 
flavor  of  smoke.     It  is  indeed  tho  presence  of  this  principle  in  wood-smoke 
which  gives  to  the  latter  its  characteristic  smell,  its  property  of  causing  lach- 
rymation,  and  its  power  of  curing  meats  and  fish.     Creosote  diluted  with 
alcohol  is  often  employed  for  relieving  toothache  arising  from  putrefactive  de- 
cay in  the  substance  of  the  tooth,  and  as  a  styptic  for  checking  hemorrhage. 
When  taken  internally  in  any  quantity  it  is  a  corrosive  poison,  but  a  very 
dilute  solution  is  sometimes  given  in  medicine.     It  is  also  extensively  em- 
ployed by  liquor  manufacturers  for  imparting  the  peculiar  smoky  flavor  to 
what  is  called  "  Irish  whiskey." 

682.  Tar . — There  are  several  varieties  of  tar.     The  kind  so  largely  em- 
ployed in  the  arts,  as  in  ship-building,  is  obtained  by  subjecting  to  a  rude 
process  of  distillation  the  roots  and  wood  of  the  resinous  pine ;  another  va- 
riety of  tar  is  obtained  from  the  destructive  distillation  of  hard  wood ;  and  a 
third  from  the  destructive  distillation  of  coal  (coal-tar). 

"Wood-tar  is  insoluble  in  water,  but  soluble  in  alcohol,  and  is  extremely 
rich  in  carbon,  which  gives  it  in  part  its  black  color.  When  applied  to  wood 
it  exerts  a  preservative  action  by  reason  of  the  creosote  it  contains,  and 
also  by  preventing  the  penetration  of  moisture.  On  distillation,  it  separates 
into  a  volatile  oil  (oil  of  tar)  and  a  non-volatile  substance,  pitch. 

From  oil  of  tar  a  great  number  of  products  may  be  extracted,  all  of  which 
are  compounds  of  carbon  and  hydrogen.  One  of  these,  called  eupion,  an 

QUESTIONS. — "What  are  the  products  which  result  from  the  distillation  of  wood  ?  What 
is  said  of  pyroligneous  acid  ?  What  of  creosote  ?  To  what  are  the  peculiar  properties 
of  smoke  due  ?  What  is  said  of  the  antiseptic  influence  of  creosote  ?  What  are  tho  uses 
of  creosote?  What  is  common  tar  the  product  of?  What  are  the  three  varieties  of  tar? 
What  are  the  properties  of  wood-tar  ?  What  are  its  products  of  distillation  ?  What  is 
said  of  the  products  of  the  distillation  of  oil  of  tar  ? 


VEGETABLE     TISSUE.  411 

oily,  fragrant  substance,  is  the  lightest  of  all  known  liquids.  Another,  pa,' 
rajine,  is  a  white,  crystallizable  substance,  closely  resembling  spermaceti  in 
appearance. 

Coal-tar  is  a  mixture  of  solid  and  liquid  hydrocarbons,  and  is  formed  abun- 
dantly in  the  production  of  illuminating  gas  from  coal,  which  is  a  vegetable 
substance.  It  was  formerly  regarded  as  a  useless  product,  but  within  the 
past  few  years  it  has  been  rendered  valuable  by  the  discovery  of  economical 
methods  of  separating  it  into  its  constituents.  This  is  principally  effected  by 
distilling  at  different  and  carefully  regulated  temperatures,  and  condensing 
the  distillates  in  the  order  of  their  volatility. 

The  first  product  of  distillation  is  a  limpid,  oily  liquid,  called  benzole.  It 
closely  resembles  oil  of  turpentine  in  appearance  and  odor,  and  is  highly 
volatile  and  inflammable.  A  current  of  moist  air  passed  through  benzole 
becomes  so  thoroughly  and  permanently  impregnated  with  its  vapor,  that  it 
may  be  conveyed  away  in  pipes  and  burned  as  an  illuminating  gas.  The 
application  of  this  property  of  benzole  constitutes  the  essential  feature  of  the 
so-called  "portable  gas  generators."  Benzole  is  also  used  to  a  considerable 
extent  as  a  most  ready  and  cheap  solvent  for  various  resins,  camphor,  the 
essential  oils,  grease,  wax,  India-rubber,  and  gutta-percha. 

The  second  important  product  of  the  distillation  of  coal-tar  is  a  heavy  oil, 
not  readily  volatile  at  ordinary  temperatures.  It  is  known  as  "  coup"  oil,  or 
heavy  oil  of  coal-tar,  and  is  extensively  used  for  the  lucubration  of  machinery, 
and  for  illuminatng  purposes. 

Similar  oils  may  also  be  obtained  in  much  larger  quantity  and  more  cheaply, 
by  directly  distilling  the  richer  varieties  of  bituminous  coal :  the  products 
known  as  "  Breckenridge  coal  oils"  being  produced  in  this  manner.  In  addition 
to  these  oils,  both  coal  and  coal-tar  also  furnish  by  distillation  a  great  variety 
of  other  products ;  among  which  are  a  white  volatile  solid  called  napthaline, 
somewhat  resembling  camphor  in  appearance,  and  exhaling  a  faint,  but 
agreeable  odor,  and  several  less  volatile  wax-like  substances,  which  have 
been  employed  to  some  extent  for  the  manufacture  of  candles. 

Coal-tar,  mixed  with  gypsum,  gum  shellac,  and  other  substances,  forms  a 
water-proof  and  durable  material  for  the  covering  of  roofs.  By  subjecting 
the  products  of  coal  and  coal-tar  to  the  action  of  chlorine  and  the  acids,  an 
almost  endless  variety  of  curious  compounds  may  be  generated,  some  of  which 
have  important  industrial  applications.  Benzole  distilled  with  nitric  acid, 
yields  a  highly  fragrant  substance  (nitro-benzole),  so  closely  resembling  the  oil 
of  bitter  almonds,  that  it  has  almost  entirely  superseded  the  latter  in  the  pre- 
paration of  perfumery  and  the  scenting  of  soaps.  The  heavy  oil  may  also  be 
converted  by  treatment  with  the  same  acid  into  a  beautiful  lemon-yellow, 


QUESTIONS. — What  is  coal-tar  ?  By  what  process  are  the  constituents  of  coal-tar  sepa- 
rated? What  is  the  first  product  of  its  distillation  ?  What  are  the  properties  of  benzole? 
What  are  its  uses  ?  What  is  coup  oil  ?  What  are  some  of  the  other  distillates  of  coal  ? 
Trom  what  other  source  beside  coal-tar  may  these  products  be  obtained?  What  is  said 
of  the  compounds  artificially  formed  from  the  distillates  of  coal  ? 


412  ORGANIC     CHEMISTRY. 

crystalline  substance  (carbazotic  acid),  which  is  capable  of  imparting  to  silk 
and  wool  a  brilliant  yellow  color. 

683.  Mineral    Oils,  Petroleum,  Naphtha,  etc. — Oils  similar  in  composi- 
tion and  properties  to  those  obtained  from  the  distillation  of  coal,  are  observed 
to  issue  from  the  earth  in  many  localities,  and  often  in  considerable  abundance. 
They  are  supposed  to  be  generated  by  the  action  of  internal  heat  upon  beds 
of  coal,  or  upon  rocks  rich  in  bituminous  matter.     The  nature  of  these  oila 
differs  greatly — the  thinner  and  purer  varieties  being  generally  called  naphtha, 
and  the  more  viscid  liquids  petroleum.     The  most  abundant  localities  of  these 
substances  are  in  Persia,  in  the  vicinity  of  the  Caspian  sea,  in  Italy,  and  in 
Birmah.     They  are  also  found  in  many  places  in  the  United  States — the  well- 
known  "  Seneca  oil,"  found  in  the  vicinity  of  Seneca  Lake,  N.  Y.,  being  a 
product  of  this  character.     At  Baku,  in  Persia,  extensive  beds  of  marl  exist 
which  are  saturated  with  naphtha,  and  in  some  parts  of  this  district  so  much 
combustible  gas  or  vapor  issues  from  the  ground,  that  it  is  used  by  the  in- 
habitants for  cooking,  and  by  certain  religious  sects  for  the  maintenance  of 
a  perpetual  fire.     Naphtha  is  somewhat  used  in  the  arts  in  the  preparation 
of  varnish,  as  a  solvent  for  certain  resins  and  India-rubber,  and  by  the  chemist 
as  a  means  of  preserving  the  metallic  bases  of  the  alkalies — potassium  and 
sodium — from  oxydation. 

684.  A  s  p  h  a  1 1  u  m — Mineral  Pitch,  Bitumen — is  another  natural  product 
undoubtedly  derived  from  the  decomposition  of  organic  matter.     It  is  a  black 
solid,  closely  resembling  petroleum,  and  melts  at  about  212°  F.     It  is  found 
abundantly  in  many  localities,  especially  in  the  vicinity  of  the  Dead  Sea  and 
in  the  island  of  Trinidad,  W.  I.,  in  which  latter  place  it  constitutes  a  lake 
three  miles  in  circumference  and  of  an  unknown  depth  ; — the  pitch  lake  of 
Trinidad. 

685.  Contents   of  the   Cells  of  Plants  .—The  contents  of  tho 
cells  of  plants  comprise  all  the  immediate  products  which  plants  produce. 

Growing  and  vitally  active  cells  are  filled  with  liquid ;  completed  cells  may 
still  be  filled  with  liquid  or  with  air,  or  with  solid  matter  only.  The  liquid 
contents  of  the  vegetable  tissues,  are  generally  spoken  of  as  sap ;  but  this 
term  does  not  specially  refer  to  any  particular  substance.  Sap,  in  the  first 
instance,  is  water  impregnated  with  certain  gaseous  matters  (carbonic  acid, 
ammonia,  etc.)  and  a  minute  quantity  of  mineral  salts,  whidi  are  imbibed  by 
the  roots  of  the  plant  from  the  soil,  and  carried  upward  through  the  stem. 
It  is,  therefore,  in  the  first  instance,  inorganic  in  its  nature.  As,  however, 
it  traverses  the  cells  of  the  plant,  it  mingles  with  the  soluble  assimilated 
matters  which  these  contain,  and  becomes  changed  in  character,  so  that  un- 
mixed, crude  sap,  is  never  met  with  in  the  plant.  On  reaching  the  leaves, 
it  becomes  further  transformed,  under  the  influence  of  light,  into  organizablo 
matter,  or  into  matter  capable  of  being  assimilated  by  the  cells  and  converted 

QUESTIONS. — What  are  mineral  oils  ?  What  names?  are  generally  applied  to  these  pro- 
ducts? What  is  said  of  their  natural  occurrence  ?  What  are  the  uses  of  naptha  ?  What 
is  asphaltum  ?  Where  is  it  found  ?  What  are  the  contents  of  the  cells  of  plants?  What 
is  s~ap?  Describe  the  successive  transformations  of  sap  ? 


VEGETABLE     TISSUE. 


413 


into  organic  products.  From  the  sap  thus  elaborated,  the  cell  manufactures, 
or  secretes,  all  the  constituents  of  the  plant. 

Of  the  non-azotized  substances  secreted  by  the  plant  cells,  the  most  abun- 
dant and  widely  distributed  is  lignine,  which  has  been  already  described.  In 
addition  to  this,  three  other  substances,  starch,  gum,  and  sugar,  closely  allied 
to  lignine  in  composition,  are  secreted  in  greater  or  less  abundance  by  al- 
most all  plants. 

686.  Starch,  C12H10Oi0. — This  substance  presents  to  the  naked  eye  the 
appearance  of  a  white  powder,  but  when  viewed  under  a  microscope  is  seen 
to  consist  of  transparent  oval  or  rounded  grains,  each  of  which  has  a  dark 
spot  at  one  extremity,  with  fine  concentric  rings  drawn  round  it.  These 
characteristic  appearances  are  best  seen  in  starch  from  the  potato,  with  a 
magnifying  power  of  from  250  to  500  diameters.  (See  Fig.  216.)  The  mag- 

FiG.  217.  FIG.  218. 


m'tude  of  the  starch  grains  varies  extremely  in  the  different  plants,  and  even 
in  the  same  cell.  Thus  in  the  potato  the  largest  grains  measure  from  l-300th 
to  l-500th  of  an  inch  in  their  larger  diameter,  but  in  the  smallest  only 
1-440 Oth  of  an  inch.  In  wheat  flour  the  larger  grains  are  from  l-800th  to 
l-900th  of  an  inch  in  diameter.  The  shape  of  the  grains  in  the  same  plant 
or  organ  is  very  nearly  uniform,  but  differs  greatly  in  different  plants;  so 
much  so,  that  mixtures  of  various  starches  may  be  easily  detected  by  the 
microscope. 

Starch,  while  an  almost  universal  product  of  all  vegetable  cells,  is  accumu- 
lated more  abundantly  in  some  species  of  plants  than  in  others.  In  the 
common  potato,  each  individual  cell  is  so  completely  filled  and  distended 
with  an  accumulation  of  starch  mingled  with  water,  that  the  whole  root  has 
an  appearance  of  deformity.  Fig.  217  represents  the  manner  also  in  which 
the  starch  grains  fill  up  the  ceUs  of  the  maize  (t.  e.,  in  Indian  meal).  Starch 
is  particularly  abundant  in  all  cereal  grains,  in  all  seeds,  in  the  pith  and  bark 
of  many  trees,  and  in  many  roots  and  tubers  (as  the  potato,  turnip,  carrot^ 
etc.).* 

*  Wheat  flour  contains  from  39  to  11  per  cent,  of  starch ;  rice  flour  about  86  per  cent.  ; 
Indian  meal  from  70  to  80  per  cent.  ;  rye  flour,  50  to  60 ;  buckwheat,  50 ;  pea  and  bean 
meal,  42 ;  and  potatoes  from  13  to  15  per  cent  of  starch,  mingled  with  about  70  parts  of 
water. 

QUESTIONS. — Beside  lignine,  what  other  non-azotized  substances  are  generally  contained 
in  the  cells  of  plants  ?  What  is  the  appearance  of  starch  ?  What  is  said  of  the  size  and 
appearance  of  its  granules  ?  In  what  vegetable  substances  is  starch  most  abundant  ? 


414  ORGANIC    CHEMISTRY. 

The  starch  of  commerce  is  usually  obtained  from  potatoes  or  wheat  The 
essential  features  of  its  process  of  manufacture  consist  in  bruising  or  grind- 
ing the  vegetable  structure  to  a  pulp,  and  then  washing .  the  mass  with  cold 
water  upon  a  sieve.  In  this  operation  the  torn  cellular  tissue  and  some 
other  constituents  are  retained  upon  the  sieve,  while  the  starch  granules  pass 
through  its  interstices  with  the  water.  From  this  liquid  the  starch  separates, 
on  standing,  as  a  fine  white  powder. 

Starch  is  insoluble  in  water,  as  its  mode  of  preparation  necessarily  implies. 
"When,  however,  a  mixture  of  starch  and  water  is  heated  to  near  its  boiling 
point,  the  granules  swell,  burst,  and  allow  their  contents  to  become  mingled 
with  the  water,  producing  thereby  a  nearly  transparent,  glutinous  mass, 
in  which  the  minute  shreds  of  membraneous  matter,  comprising  the  cell- walls, 
float.  The  rounded  and  swollen  appearance  which  potatoes,  peas,  rice,  and 
most  other  vegetables  assume  when  boiled,  is  due  to  a  distension  of  their 
starch  granules  through  an  absorption  of  water  at  the  boiling  temperature. 

The  chemical  test  of  starch  is  iodine,  which  'forms  with  it  a  beautiful  blue 
compound,  insoluble  in  water.  This  reaction  may  be  strikingly  illustrated 
by  adding  to  a  tumbler  of  pure  water  a  single  drop  of  gelatinous  starch,  and 
then  stirring  the  mixture  with  a  glass  rod  moistened  with  an  alcoholic  solu- 
tion of  iodine. 

The  chemical  composition  of  starch  is  exactly  the  same  as  that  of  cellulose, 
and  it  appears  to  be  especially  the  ready  prepared  material  of  vegetable  fabric, 
which  the  plant  accumulates  in  cells  as  a  provision  for  future  growth. 

The  substances  known  as  sago,  tapioca,  and  arrow-root,  are  only  varieties 
of  starch ;  the  former  being  obtained  from  the  pith  of  various  species  of  the 
palm,  and  the  two  latter  from  the  roots  of  certain  tropical  plants. 

687.  Dextrine,  —  When  thick  gelatinous  starch  is  boiled  for  a  few 
minutes  with  a  small  quantity  of  dilute  acid,  as  sulphuric  acid,  for  example, 
it  speedily  loses  its  viscidity,  and  becomes  changed  into  a  fluid  as  thin  and 
limpid  as  water.  If  the  acid  be  now  withdrawn,  by  saturation  with  chalk 
(which  combines  with  it  to  form  insoluble  sulphate  of  lime),  and  the  liquid 
be  gently  evaporated  to  dryness,  it  furnishes  a  substance  resembling  gum, 
which  is  termed  dextrine.*  This  new  body  is  freely  soluble  hi  cold  water, 
and  has  exactly  the  same  composition  as  gelatinous  starch,  but  is  not  colored 
by  iodine. 

If,  instead  of  interrupting  the  action  of  the  acid  upon  the  starch  as  soon 
as  the  mixture  has  become  clear  and  thin,  we  continue  the  ebullition  for  sev- 
eral hours,  adding  from  time  to  time  small  quantities  of  water  to  supply  the 


*  Dextrine,  so  called  from  the  circumstance  that  when  a  team  of  polarized  light  is 
passed  through  its  solution,  it  causes  the  plane  of  polarization  to  turn  to  the  right. 

QUESTIONS.— From  what  sources  is  it  generally  obtained  ?  How  is  starch  manufac- 
tured ?  When  starch  is  boiled  in  water,  what  takes  place  ?  What  is  the  chemical  test  of 
starch  ?  What  is  its  chemical  composition  ?  What  is  sago,  tapioca,  and  arrow-root  ? 
What  is  dextrine  ?  How  is  starch  converted  into  dextrine  ?  How  is  dextrine  converted 
into  sugar  ? 


VEGETABLE     TISSUE.  415 

place  of  that  lost  by  evaporation,  and  finally,  neutralizing  the  acid  by  chalk, 
filter  and  boil  down  the  clear  solution  to  a  small  bulk,  we  obtain  a  syrupy 
liquid,  which  on  standing  for  a  few  days,  entirely  solidifies  to  a  mass  of 
grape-sugar,  exceeding  in  weight  the  starch  from  which  it  was  produced. 

How  this  transformation  of  starch  into  dextrine,  and  dextrine  into  sugar, 
is  effected  is  not  fully  understood.  The  acid  employed  undergoes  neither 
change  nor  diminution,  and  if  not  volatile  may  bo  recovered,  without  loss,  after 
the  conclusion  of  the  experiment ;  nothing,  moreover,  is  withdrawn  from  tho 
air,  and  no  other  substances  but  dextrine  and  grape-sugar  are  generated. 
Chemists,  therefore,  have  very  generally  adopted  the  conclusion  that  the  acid 
occasions  the  transformation  and  change  in  question  by  its  mere  presence, 
and  the  phenomenon  is  cited  as  an  example  of  catalysis.  (§  255,  p.  161.) 
Spongy  platinum,  as  has  been  already  pointed  out  (§  296),  apparently  acts 
in  a  similar  manner,  and  is  capable  of  exciting  chemical  activity  in  contiguous 
substances  without  being  itself  affected.  In  the  case  of  the  dextrine,  as  its  chem- 
ical composition  is  precisely  the  same  as  that  of  starch,  the  difference  in  prop- 
erties is  referred  to  a  change  in  the  arrangement  of  its  constituent  atoms  of 
carbon,  hydrogen,  and  oxygen.  In  the  conversion  of  the  dextrine  into  sugar, 
the  change  seems  to  be  effected  by  a  fixation  or  incorporation  into  the  for- 
mer substance  of  an  additional  quantity  of  the  elements  of  water,  hydrogen 
and  oxygen — as  the  sugar  thus  produced  sensibly  exceeds  in  weight  the 
starch  employed. 

688.  Diastase . — There  are,  however,  several  other  methods  by  which 
these  same  changes  in  starch  may  be  effected,  in  addition  to  the  one  noticed. 
Thus,  all  seeds  in  the  act  of  germinating,  and  all  buds  in  developing,  pro- 
duce from  the  nitrogen  compounds  which  they  contain  a  very  peculiar  sub- 
stance called  disastase.  This  body,  which  the  chemist  has  never  yet  been 
able  to  fully  isolate,  possesses  the  same  power  as  the  dilute  acid  of  converting 
a  large  quantity  of  starch,  first  into  dextrine  and  then  into  sugar.  Its  ac- 
tion, however,  takes  place  at  a  much  lower  temperature  than  that  of  ebul- 
lition. 

This  fact  may  be  experimentally  shown  by  mixing  a  little  infusion  of  malt 
(germinated  barley)  with  a  considerable  quantity  of  thick  starch  paste,  and 
subjecting  the  whole  to  a  gentle  heat  not  exceeding  160°  P.  In  a  few  min- 
utes the  mixture,  from  the  production  of  dextrine,  becomes  thin  like  water, 
and  if  the  temperature  be  kept  up  during  three  or  four  hours,  the  liquid  will 
be  found  to  have  acquired  a  sweet  taste,  and  to  be  rich  in  sugar.  The  quan- 
tity of  dextrine  necessary  to  effect  this  change  is  very  small — one  part  in  two 
thousand  parts  of  starch  being  sufficient  to  entirely  convert  the  latter  into 
sugar.  A  boiling  heat  coagulates  the  diastase,  and  by  rendering  it  insoluble 
destroys  its  power. 

The  well-known  sweet  taste  which  fruits  acd  vegetables  acquire  by  freez- 


Q0ESTION6. — What  is  said  of  these  transformations  ?  How  do  germinative  seeds  and 
buds  act  upon  starch  ?  What  is  disastase  ?  How  may  its  properties  be  illustrated  ?  Why 
are  frozen  thawed  fruits  and  regetables  sweet  ? 


416  ORGANIC    CHEMISTRY. 

ing  and  thawing,  is  due  to  the  fact  that  the  starch  which  they  contain  is 
converted,  in  part,  by  the  action  of  the  frost,  into  sugar. 

689.  Dextrine  is  used  extensively  in  the  arts  as  a  substitute  for  gum ;  i.  e.7 
for  the  stiffening  and  glazing  of  muslins,  in  calico-printing,  and  in  the  printing 
of  wall-papers.  It  is  manufactured  for  industrial  purposes  by  simply  roasting 
dry  potato-starch,  or  subjecting  it  to  a  heat  of  about  400°  F.  By  this  treat- 
ment the  starch  acquires  a  yellowish  tint  and  is  rendered  soluble  in  water. 
Dextrine  occurs  in  commerce-  under  the-  name  of  "  British  gum}1 

690.'  (i  11  m  , — In  addition  to  dextrine,  which  is  found  in  greater  or  less 
quantity  in  the  juices  of  every  plant,  the  term  gum  is  generally  applied  to 
designate  certain  vegetable  substances  which  possess  the  same  elementary 
composition  as  starch,  and  which  are  soluble  in  water,  but  not  in  alcohol. 
In  some  plants  they  exist  so  abundantly,  that  they  exude  from  the  bark  as 
viscid  liquids,  which  subsequently  harden  into  transparent,  globular  masses. 
Familiar  illustrations  of  this  may  be  noticed  on  peach  and  cherry  trees.  Tho 
term  resin  is  rightly  applied  to  those  hardened  vegetable  juices  only  which 
do  not  soften  or  dissolve  in  water,  but  are  soluble  in  alcohol. 

The  most  important  gums  of  commerce  are  gum  arable,  gum  Senegal,  and 
gum  tragacanth. 

Gum  arabic  is  the  product  of  a  species  of  acacia  which  grows  abundantly 
in  Africa  and  Arabia ;  gnm  Senegal,  the  product  of  a  similar  tree,  derives 
its  name  from  Senegal,  in  Africa,  the  district  from  which  it  was  originally 
exported.  Both  of  these  gums  are  freely  soluble  in  water,  and  form  with  it 
a  mucilage  much  used  for  paste ;  the  mucilage  yielded  by  gum  Senegal  being 
somewhat  thicker  than  that  formed  by  gum  arabic.  The  pure  gummy  sub- 
stance contained  in  them  may  be  precipitated  from  its  solution  in  water  by 
alcohol,  and  is  termed  arabine. 

Gum  tragacanth  is  the  product  of  a  shrub  found  extensively  in  Asia  Minor 
and  Persia,  and  is  composed  mainly  of  a  substance  termed  lasorine.  It  swells 
very  much  in  water,  and  forms  a  thick  adhesive  paste,  but  can  hardly  be  said 
to  dissolve  in  it.  It  is,  however,  soluble  in  caustic  alkalies. 

Gum  is  an  essential  constituent  of  the  cereals,  and  of  most  seeds,  and  is 
abundant  in  many  vegetables.  "Wheat  flour  contains  about  3  per  cent.;  rye 
flour,  11;  Indian  corn,  2*2;  peas,  6 -3;  kidney  beans,  19;  potatoes,  3*3; 
cabbage,  2-8. 

691.  Mucilage  , — Many  seeds,  as  flax  seed,  and  many  roots,  barks,  and 
leaves  of  plants,  as  slippery-elm  bark,  marsh  mallow,  etc.,  yield,  .when  di- 
gested with  water,  gummy  and  stringy  liquids.     To  such  products  the  gen- 
eral name  of  vegetable  mucilage  has  been  applied,  and  their  chemical  com- 
position is  believed  to  be  the  same  as  that  of  starch  and  gum. 

692.  P  e  c  t  i  n  e ,  or  pectic  acid,  is  a  gelatinous  substance  found  in  the 

QUESTIONS.— What  are  the  uses  of  dextrine  ?  What  is  "  British  gum  f '  To  what  other 
substances  is  the  term  gum  applied  ?  How  does  a  gum  differ  from  a  resin  ?  What  are 
the  principal  gums  of  commerce?  From  whence  are  they  derived  ?  What  are  their  gen- 
eral properties  ?  What  is  said  of  the  general  occurrence  of  gum  as  a  vegetable  product? 
What  is  mucilage  ?  What  is  pectine  ? 


SUGAR,  417 

juices  of  all  ripe  fleshy  fruits,  and  allied  in  composition  to  starch,  gum,  and 
mucilage.  It  is  the  agent  which  communicates  to  the  juices  of  fruits  the 
property,  when  boiled  (especially  in  connection  with  sugar)  and  cooled,  of 
hardening  into  jelly,  and  is  hence  sometimes  called  "  vegetable  jelly." 

693.  Sugar  . — The  term  sugar  is  ordinarily  used  to  designate  the  sweet 
principle  of  plants,     The  chemist,  however,  at  the  present  day  applies  it  to  a 
large  number  of  bodies,  which  differ  greatly  from  one  another  in  their  prop- 
erties.    Thus  we  have  sugars  which  are  derived  from  both  vegetable  and 
animal  organisms — sugars  which  are  sweet,  sugars  which  are  slightly  sweet, 
and  some  which  are  destitute  of  sweetness ;  some  sugars,  also,  are  capable 
of  fermentation,  others  do  not  undergo  this  change ;  some  are  fluid,  but  most 
are  solid.     All  sugars,  however,  agree,  with  perhaps  a  single  exception,  in  one 
respect — they  consist  of  carbon,  hydrogen,  and  oxygen,  with  the  two  latter 
elements  united  to  the  former  in  exactly  the  proportions  which  form  water. 

Sugar  exists  in  greater  or  less  abundance  in  all  plants,  and  it  is  from  this 
source  only  that  we  obtain  our  supplies.  It  abounds  most  in  the  growing 
parts,  in  the  stems  just  before  flowering,  as  those  of  the  sugar-cane,  maize, 
maple,  etc.,  in  pulpy  fruits,  and  in  seeds  when  they  germinate.  Like  starch, 
it  appears  to  be  a  material  especially  intended  to  subserve  the  growth  and 
nourishment  of  the  plant ;  but  unlike  it,  it  exists  in  the  plant  only  in  solution. 

All  the  numerous  varieties  of  sugar  may  be  conveniently  arranged  in  four 
classes,  viz.,  the  cane  sugars,  the  grape  sugars,  the  manna  sugars,  and  the 
sugar  of  milk. 

694.  Cane    Sugar,  Ci2HnOu.— This  variety  of  sugar  includes  the  sugar 
of  the  sugar-cane,  beet  sugar,  palm  or  date  sugar,  maple  sugar,  and  the  sugar 
of  the  maize  and  of  the  fully  ripe  sorghum.     It  is  also  found  in  many  of  our 
common  meadow  grasses,  and  in  the  juices  of  melons,  carrots,  and  turnips. 
Plants  which  have  but  little  acid  in  their  sap  contain  for  the  most  part  cane- 
sugar  ;  the  chemical  reason  of  this  is,  that  cane  sugar,  by  the  action  of  acid 
substances,  is  gradually  converted  into  grape  sugar,  even  in  the  interior  of 
the  growing  plant. 

About  eleven  twelfths  of  all  the  sugar  extracted  for  use  is  obtained  from 
the  sugar-cane,  and  the  yearly  production  from  this  source,  over  the  whole 
globe,  has  been  estimated  at  4,500,000,000  Ibs.  Of  this  enormous  quantity, 
the  population  of  Great  Britain  are  certainly  known  to  consume  at  least  two 
elevenths.  The  method  of  manufacturing  sugar  from  the  cane  (and  also  from 
the  beet)  is  essentially  as  follows :  the  juice  extracted  from  the  vegetable 
structure  by  pressure,  is  mixed  with  a  small  quantity  of  hydrate  of  lime 
(slacked  lime),  and  rapidly  heated  to  near  the  boiling  point.  The  action  of 
the  lime  is  twofold :  it  removes  or  neutralizes  the  acid  which  rapidly  forms  in 
the  fresh  juice,  and  at  the  same  time  unites  with  and  precipitates  the  glutin- 

QTTESTICXNS. —  What  is  its  most  noticeable  property  ?  What  is  the  ordinary  signification 
of  the  term  sugar?  Is  the  term  restricted  in  a  chemical  sense  to  any  particular  sub- 
stance  ?  In  what  respect  do  all  sugars  agree  ?  What  is  said  of  the  natural  occurrence  of 
sugar?  Into  what  four  classes  may  all  sugars  be  divided ?  What  sugars  are  included 
under  the  name  of  cane  sugars  ?  How  is  cane  sugar  manufactured  ?  Why  is  lime  used  ? 


418  ORGANIC    CHEMISTRY. 

ous  matters  contained  in  the  juice,  The  removal  of  these  latter  substances  is 
an  essential  part  of  the  process,  as  a  short  exposure  to  the  atmosphere  occa- 
sions their  fermentation,  which  in  turn  converts  the  sweet  juice  into  a  sour 
and  spirituous  liquid,  totally  unfit  for  the  manufacture  of  sugar.  The  juice, 
after  clarification,  is  rapidly  evaporated  in  open  pans  to  a  thick  syrup,  and 
then  run  into  wooden  vessels  to  cool  and  crystallize,  and  finally,  when  crys- 
tallized, is  allowed  to  drain  in  perforated  casks*  The  product  remaining  after 
drainage,  is  the  common  raw  or  brown  sugar,  while  the  drainings  constitute 
molasses. 

695.  Molasses  is  uncrystallizable  sugar,     It  does  not  pre-exist  in  the 
juice  of  the  cane,  but  is  produced  at  the  expense  of  the  crystallizable  sugar, 
mainly  by  the  high  temperature  used  in  the  concentration  of  the  sacchar- 
ine solution.     In  improved  processes  for  the  manufacture  of  raw  sugar,  and 
always  in  the  refining  of  sugars,  the  boiling  of  the  syrups  is  conducted  in 
what  are  called  "  vacuum  pans,"  which  are  large  metallic  boilers  so  con- 
structed that  they  can  be  exhausted  of  air.     The  boiling  point  of  the  syrup, 
owing  to  the  absence  of  atmospheric  pressure,  is  thus  reduced  to  about 
150°  F.,  and  the  formation  of  molasses  almost  entirely  prevented. 

The  process  of  manufacturing  raw  sugar,  although  apparently  most  simple, 
is  attended  with  many  difficulties  in  practice ;  so  much  so,  that  of  the  18  per 
cent,  of  sugar  contained  hi  the  cane  juice  of  the  "West  India  Islands,  not 
more  than  6  per  cent.,  or  one  third  of  the  whole,  is  usually  sent  to  market  hi 
the  state  of  crystallizable  sugar. 

696.  The   Refining  of  Sugar  is  not  generally  carried  on  in  connec- 
tion with  manufacture  of  the  crude  product.    It  is  effected  by  dissolving  tho 
brown  sugars  in  water,  adding  albumen  (whites  of  eggs,  or  bullocks'  blood), 
and  sometimes  a  little  lime-water,  and  heating  the  whole  to  the  boiling  point. 
The  albumen,  under  the  influence  of  heat,  coagulates,  and  forms  a  kind  of  net- 
work of  fibers,  which  inclose  and  separate  from  the  liquid  all  the  mechanically 
suspended  impurities.     The  solution  is  then  decolorized  by  filtering  through 
animal  charcoal,  concentrated  by  evaporation  in  vacuum  pans,  and  allowed  to 
crystallize  in  conical  iron  molds.     The  molasses,  or  drainings  which  escape 
from  refined  sugar,  by  means  of  orifices  opened  in  the  bottom  of  these  molds, 
is  sold  under  the  name  of  Sugar-house  Syrup,  Stuart's  Syrup,  etc.     The  time 
required  for  the  perfect  crystallization  and  separation  of  the  white  sugar  in  tho 
molds  is  from  18  to  20  days,  during  which  period  the  syrup  is  frequently 

stirred  in  order  to  prevent  the  formation  of  crystals  of  a 

FIG.  218.       iarSe  8ize- 

697.  Sugar   Candy  .—"When  a  strong  solution  of  re- 
fined sugar  is  allowed"  to  evaporate  slowly  and  uninterrupt- 
edly, the  sugar  separates  in  the  form  of  large,  transparent, 
colorless  crystals,  having  the  form  of  an  oblique,  six-side 
prisms.     See  Fig.    218.      In  this  state   it  is  known 
"  Sugar,"  or  "  Rock  Candy." 

QUESTIONS.— What  i«  molasses  ?    How  is  it  formed  ?    How  is  sugar  refined  f    What 
Sugar  candy? 


SUGAR.  419 

In  many  parts  of  Europe,  especially  in  France,  sugar  is  extensively  manu- 
factured from  the  beet  root,  the  juice  of  which  contains  about  8  per  cent,  of 
cane  sugar.  At  the  present  time,  about  360  millions  of  pounds  of  sugar  are 
annually  obtained  from  this  source  on  the  continent  of  Europe,  or  about  7  per 
cent,  of  all  the  sugar  consumed  in  the  world. 

The  amount  of  sugar  annually  extracted  from  the  date  palm  (principally  in 
India  and  the  South  Pacific),  is  estimated  at  220  millions  of  pounds;  while 
the  quantity  annually  obtained  from  tho  sugar  maple  of  North  America  is 
about  45  million  pounds. 

698.  When  cane  sugar  is  heated  to  about  400°  F.,  it  gives  up  two  equiva- 
lents of  hydrogen  and  oxygen  (water),  and  is  converted  into  a  dark-brown 
substance,  termed  caramel     This  body  is  freely  soluble  in  alcohol  and  water, 
and  is  extensively  used  for  the  coloration  of  spirits — the  color  of  all  dark 
brandies  being  due  to  it 

699.  Grape   S  u  g  a  r. —  Glucose;  Sugar  of  Fruits,  CisHuOw. — This  var- 
iety of  sugar  includes  the  sugar  of  grapes,  of  ripe  fruits,  of  honey,  and  of  seeds ; 
together  with  the  sugars  artificially  produced  from  starch  and  woody  fiber. 
It  is  more  generally  diffused  in  nature  than  cane  sugar,  and  is  the  product  of 
most  plants  which  contain  acids  or  sour  juices. 

The  white  coating  upon  dried  grapes  (raisins),  figs,  etc. ;  and  the  white, 
brittle  granules  found  in  tho  interior  of  these  fruits,  is  grape  sugar; — hence 
the  origin  of  the  name. 

Grape  sugar  may  be  abundantly  obtained  from  the  juice  of  ripe  grapes  and 
pure  honey,  by  washing  with  cold  alcohol,  which  dissolves  the  fluid  syrup. 
It  may  also  be  prepared  by  treating  starch  with  sulphuric  acid  in  the  manner 
already  described  •  sugar  from  this  source  has  received  the  distinctive  name 
of  glucose,  and  is  very  largely  employed  in  Europe  for  ordinary  sweetening 
purposes,  for  confectionary,  for  adulterating  cane  sugar,  and  for  the  manufac- 
ture of  spirituous  liquors  by  fermenting  and  distilling.  In  the  United  States, 
the  low  price  of  cane  sugar  renders  its  manufacture  unprofitable. 

In  addition  to  starch,  woody  fiber  of  all  kinds,  paper,  cotton,  flax,  cotton  and 
linen  rags,  and  even  saw-dust,  may  be  converted  into  grape  sugar  by  heating 
in  connection  with  dilute  sulphuric  acid.  The  operation  is  somewhat  slower 
than  when  starch  alone  is  employed,  which  is  partially  explained  by  the  fact, 
that  the  acid  first  changes  the  woody  fiber  into  starch,  and  then  the  starch 
into  dextrine  and  sugar. 

Almost  all  the  acids,  even  when  very  dilute,  convert  cane  sugar  into  grapo 
sugar. 

Grape  sugar  is  sometimes  produced  in  the  animal  system,  and  its  appear- 
ance in  the  urine  in  great  quantities  is  a  characteristic  feature  of  a  very  fatal 
disease  termed  diabetes. 

QUESTIONS. — What  is  said  of  the  production  of  beet,  date,  and  maple  sugars  ?  What  is 
caramel  ?  What  are  grape  sugars  ?  What  are  familiar  examples  of  grape  sugar  ?  How 
may  it  be  prepared?  What  other  substances  besides  starch  may  yield  grape  sugar? 
What  is  the  action  of  acids  upon  cane  sugar  ?  Does  grape  sugar  ever  occur  in  the  animal 
system  T 


420  ORGANIC     CHEMISTRY. 

700.  Essential  Differences  of  Cane  and  Grape  Sugars. 

— Cane  sugars  are  popularly  distinguished  from  every  other  variety  of  sugars 
by  their  greater  sweetness  or  sweetening  power ;  three  parts  being  equivalent 
in  this  respect  to  five  of  grape  sugar.  Cane  sugar  dissolves  more  readily  in 
water  than  grape  sugar ;  one  pound  of  cold  water  dissolving  three  pounds  of 
the  former  and  but  one  of  the  latter.  Cane  sugar,  when  pure,  remains  dry 
and  unchanged  in  the  air,  crystallizes  readily,  and  when  acted  upon  by  sul- 
phuric acid,  is  blackened;  grape  sugar,  on  the  contrary,  absorbs  moisture 
from  the  atmosphere,  and  becomes  damp ;  is  not  easily  crystallized,  and  when 
digested  in  sulphuric  acid,  dissolves  freely  without  blackening. 

As  respects  chemical  composition,  cane  sugar  differs  from  starch  and  woody 
fiber  in  simply  containing  an  additional  equivalent  of  the  elements  of  water — 
the  formula  of  the  latter  being  Ci2Hi0Oio,  while  that  of  cane  sugar  is  C12HnOn. 
Grape  sugar  contains  relatively  less  carbon  than  either  starch  or  cane  sugar, 
its  formula  being  Ci2Hi4Oi4. 

Grape  sugar  may  be  prepared  artificially  from  various  substances,  but  cane 
sugar  can  not  be  so  obtained. 

These  two  varieties  of  sugar  may  be  easily  distinguished  from  each  other 
by  their  reactions  with  oxyd  of  copper:  thus,  if  we  add  to  separate  solutions 
of  cane  and  grape  sugars  a  few  drops  of  sulphate  of  copper  (blue  vitriol),  and 
afterward  caustic  potash  in  excess,  we  obtain  deep-blue  liquids,  which  ex- 
hibit very  different  characters  when  heated;  the  solution  of  cane  sugar  re* 
tains  its  blue  color,  while  that  of  grape  sugar  throws  down  a  copious  reddish 
precipitate  of  suboxyd  of  copper. 

Sugar  often  acts  the  part  of  an  acid,  and  is  capable  of  uniting  with  bases — • 
potash,  baryta,  lime,  etc. — to  form  salts  called  saccharates.  Most  of  the  sugars, 
when  left  in  contact  with  certain  nitrogenized  substances,  called  yeasts  or  fer- 
ments, become  decomposed,  and  pass  into  alcohol  and  carbonic  acid.  Grape 
sugar  is  especially  susceptible  of  this  change;  and  cane  sugar,  before  it  under- 
goes fermentation,  always  passes  into  grape  sugar. 

101.  Manna  Sugars,  Cc  H7  05 ,  are  distinguished  from  other  sugars  in 
three  particulars :  they  do  not  contain  hydrogen  and  oxygen  united  to  carbon 
in  the  proportions  which  form  water ;  they  are  inferior  in  sweetness  to  other 
sugars;  and  they  do  not  ferment  under  the  influence  of  yeast.  Manna  sugars 
are  somewhat  extensively  distributed  in  the  vegetable  organization,  and  exist 
most  abundantly  in  manna,  which  is  a  dried  juice  of  certain  species  of  ash- 
trees  growing  in  southern  Europe.  They  are  also  found  in  the  juices  of  the 
onion,  asparagus,  celery,  mushrooms,  and  in  several  sea- weeds;  and  may  be 
artificially  prepared  from  ordinary  sugar  by  a  peculiar  kind  of  fermentation. 

702.  Sugar  of  Milk .—Lactine,  C^H^C^.— This  peculiar  substance  is 
the  sweet  principle  of  milk.  When  the  curd  ia  separated  in  the  making  of 

QUESTIONS.— What  are  the  essential  differences  of  cane  and  grape  sugar?  By  what 
chemical  test  may  the  two  be  distinguished  ?  How  does  sugar  comport  itself  as  respects 
the  bases.?  What  is  a  property  of  most  sugars  ?  What  are  the  characteristics  of  manna 
sugar*  ?  What  is  said  of  their  occurrence  ?  What  is  said  of  the  sugar  of  milk  2 


ALBUMEN.  421 

cheese,  the  sugar  remains  in  the  whey,  and  may  be  obtained,  in  the  form  of 
white  prismatic  crystals,  by  evaporating  the  whey  to  a  small  bulk,  and  allow- 
ing it  to  cool.  It  is  much  less  soluble  and  less  sweet  than  cane  sugar,  and  in 
a  solid  state  feels  gritty  between  the  teeth.  It  is  principally  manufactured  in 
Switzerland,  and  is  used  extensively  in  homoeopathic  medicine,  as  envelope 
for  remedial  substances.  It  has  hitherto  been  detected  in  only  one  vegetable 
production — the  acorn. 

703.  The  conversion  of  starch  into  gummy  matter  and  sugar,  and  that  of 
the  latter  into  starch,  is  a  very  common  result  in  the  vegetable  kingdom. 
Unripe  fruit,  as  apples,  pears,  etc.,  contain  an  abundance  of  starch  ;  this  may 
be  proved  by  applying  the  tincture  of  iodine  to  a  freshly-cut  surface.     When 
the  fruit  is  completely  ripened,  this  reaction  can  not,  however,  be  obtained ; 
the  starch,  therefore,  has  disappeared,  and  has  been  replaced  by  sugar,  as  ia 
made  evident  by  the  sweet  taste  which  the  fruits  have  acquired.* 

SECTION    II. 

ALBUMEN,  CASEIN  E,  GLUTEN. 

704.  Associated  with  the  non-azotized  substances  in  all  plants,  is  another 
class  of  compounds,  equally  important,  but  much  less  abundant,  than  the  for- 
mer.    These  are  the  nitrogenized  or  albuminous  compounds,  the  principal  of 
which  are  known  as  Albumen,  Caseine,  and  Gluten. 

705.  Albumen  is  widely  disseminated  through  vegetable  structures,  and 
also  exists  abundantly  in  the  animal  economy ;  the  white  of  eggs,  and  the 
serum,  or  thin,  transparent  part  of  the  blood,  being  essentially  composed  of 
albumen  dissolved  in  water. 

Albumen  dissolves  freely  in  cold  water,  and  forms  a  tasteless,  glairy,  trans- 
parent fluid;  if  heated,  however,  to  about  158°  R,  it  coagulates,  or  becomes 
insoluble  in  either  hot  or  cold  water.  This  change  may  be  especially  noticed 
in  the  cooking  of  eggs.  Alcohol,  creasote,  corrosive  sublimate,  and  many 
other  substances,  are  also  capable  of  transforming  ablumen  from  a  soluble  into 
an  insoluble  condition. 

*  "  A  similar  metamorphosis  is  also  noticed  in  the  potato.  The  quantity  of  starch  con- 
tained in  100  Ibs.  of  the  same  kind  of  potatoes  has  been  found  to  be  in  August,  10  pounds; 
in  September,  14;  in  October,  15;  in  November,  16  ;  in  December,  IT;  in  January,  17; 
in  February,  16 ;  in  March,  15  ;  in  April,  13 ;  in  May,  10.  Accordingly,  the  quantity  of 
starch  in  potatoes  increases  during  the  autumn,  remains  stationary  daring  the  winter,  and 
in  the  spring,  after  the  germinating  principle  is  excited,  it  diminishes.  It  is  a  well-known 
fact,  that  in  germination,  potatoes  become  soft,  mucilaginous,  and  afterward  sweet ;  the 
dextrine  formed  from  the  starch  rendering  them  mucilaginous,  and  the  sugar  formed 
from  the  dextrine  rendering  them  sweet  The  process  of  transformation  advances  still 
further  in  the  earth  ;  the  potatoes  becoming  softer  and  more  watery,  and  when  the  starch 
is  completely  consumed  in  the  growth  of  the  young  plant,  the  process  of  decay  com- 
mences."— STOCKHABDT. 

QUESTIONS. — What  fact  illustrates  the  conversion  of  starch  into  sugar  in  nature  ?  What 
are  the  principal  nitrogenized  compounds  of  plants  ?  What  is  said  of  albumen  ?  What 
are  its  characteristic  properties?  Why  do  eggs  harden  in  boiling? 


422  ORGANIC     CHEMISTRY. 

When  water  containing  a  small  portion  of  albumen  is  heated,  the  albumen 
is  coagulated,  and  rises  as  a  scum  to  the  surface,  carrying  with  it  any  small 
particles  of  impurity  mechanically  suspended  in  the  liquid.  It  is  in  this  way 
used  for  clarifying  solutions  of  sugar  and  other  liquids. 

Albumen  is  found  in  a  soluble  state  in  the  sap  of  plants,  in  the  humors  of 
the  eye,  in  the  white  of  eggs,  and  in  the  serum  of  the  blood ;  and  in  an  in- 
soluble state  in  the  seeds,  leaves,  and  stalks  of  plants,  and  in  the  substance  of 
which  the  brain  and  nerves  of  animals  are  composed. 

706.  Caseine  is  a  substance  of  both  vegetable  and  animal  origin,  and  is 
allied  to  albumen  in  its  composition  and  properties.     It  differs  from  it,  how- 
ever, in  the  circumstance  that  it  is  not  coagulated  by  heat,  although  it  readily 
experiences  this  change  under  the  influence  of  acids.     It  is  found  abundantly 
in  the  seeds  of  leguminous  plants;  peas  and  beans  containing  from  20  to  25 
per  cent,  of  their  weight  of  it     It  also  exists  in  animal  substances,  especially 
in  the  curd  of  milk,  which  is  known  as  animal  caseine,  and  is  the  chief  ingre- 
dient in  cheese.     Vegetable  caseine,  to*  distinguish  it  from  animal  caseine,  is 
often  called  legumine,  but  the  identity  of  the  two  is  well  illustrated  by  the  fact 
that  the  Chinese  make  a  real  cheese  from  peas.     Vegetable  caseine  may  be 
obtained  by  macerating  peas  or  beans  in  tepid  water  for  several  hours,  and 
straining  through  a  seive.     The  liquid  which  passes  through  contains  caseino 
in  solution,  together  with  some  starch,  which  separates  by  standing.     From 
the  supernatant  liquor,  which  resembles  skimmed  milk  in  appearance,  caseino 
may  be  precipitated  by  the  addition  of  acetic  acid,  and  when  washed  and 
dried,  forms  a  brilliant,  transparent  mass, 

707.  Gluten . — If  flour  be  made  into  dough,  and  worked  with  the  hand 
upon  a  seive,  or  piece  of  muslin,  under  a  stream  of  water  (Fig.  219),  its  starch 
gradually  washes  away,  and  there  remains  upon  the  seive  a  white,  soft  sticky 
substance,  which  has  received  the  name  of  gluten.     This  substance  exists  in 
all  the  cereal  grains,  and  constitutes  about  10  per  cent,  of  the  weight  of  pure 
flour,  and  from  14  to  15  per  cent  of  the  weight  of  bran.     It  is  this  principle 
which  imparts  to  flour  its  plastic  and  adhesive  properties. 

The  lean  part  of  the  muscles  of  all  animals,  termed  fibnne,  resembles  the 
gluten  of  plants  so  closely  in  composition  and  properties,  that  it  may  be  re- 
garded as  essentially  the  same  substance,  and  hence  gluten  is  very  often 
called  vegetable  fibrine. 

708  Chemical  Composition  of  Proteine.  —  Albumen  and 
gluten  are  composed  of  carbon,  hydrogen,  oxygen,  nitrogen,  phosphorus,  and 
sulphur;  caseine  contains  the  same  elements,  in  nearly  the  same  proportions, 
with  the  exception  of  phosphorus,  which  does  not  enter  into  its  composition. 

According  to  the  generally  received  opinion  at  the  present  day,  all  album- 

QTTESTIONS — How  is  albnmen  employed  for  the  clarifying  of  liquids  ?  What  is  said  of 
caseine?  In  what  respect  does  it  chiefly  differ  from  albumen?  In  what  vegetable  sub- 
stances does  it  especially  occur  ?  In  what  animal  substance  ?  By  what  other  name  is 
vegetable  caseine  known  ?  How  may  caseine  be  obtained  ?  What  is  gluten  ?  In  what 
vegetable  products  is  gluten  especially  found  ?  With  what  substance  of  animal  origin 
does  it  correspond  ?  What  is  the  chemical  composition  of  albumen,  caseine,  and  gluten  ? 


ALBUMEN,     CASEINE.     GLUTEN. 


423 


inous  matter  (and  by  this  terra  FiG,   219. 

we  mean  to  include  albumen, 
caseine,  gluten,  and  all  similar 
substances,  originating  either  in 
vegetable  or  animal  structures) 
are  compounds  of  a  peculiar  and 
distinct  principle,  called proteine. 
The  composition  of  this  organic 
radical  is  indicated  by  the  for- 
mula CseHssjSLiOio,  or  by  the 
symbol,  Pr.  Hence,  albuminous 
substances,  as  a  class,  are  very 
generally  termed  proteine  com,' 
pounds-— the  formula  of  albumen 
being  10Pr-{-P-|-S ;  of  gluten, 
lOPr-|-P-f-2S;  and  of  caseine, 
lOPr-f-S.* 

By  dissolving  any  albuminous 
Substance  in  caustic  alkali,  and 
adding  acetic  acid  to  the  solution,  proteine  may  be  precipitated  in  the  form 
of  a  grayish-white,  inodorous  solid,  soluble  in  water  and  alcohol,  and  capable 
of  uniting  to  form  compounds  with  many  acids  and  bases. 

709.  Characteristics  of  the  Albuminous  Substances, 
• — All  the  albuminous  substances,  when  subjected  to  heat,  exhale  an  odor 
similar  to  that  of  burnt  feathers,  and  leave,  as  an  ultimate  residue,  a  black, 
brilliant,  spongy  coal.  When  perfectly  dried,  they  are  capable  of  indefinite 
preservation ;  but  when  exposed  to  the  joint  influence  of  air  and  moisture, 
they  are  more  susceptible  of  decomposition  than  any  other  class  of  organic 
substances — putrefying  and  calling  into  existence  a  multitude  of  microscopic 
animalculso.  The  decomposition  of  the  albumen  contained  in  wood,  espe- 
cially in  what  is  called  the  sap-wood,  is  regarded  as  the  most  active  cause  of 
its  decay.  Hence  those  substances  like  creosote,  corrosive  sublimate  and  the 
like,  which  form  insoluble  compounds  with  albuminous  matter,  existing  either 
m  animal  or  vegetable  tissues,  are  the  most  effectual  antiseptic  agents ;  the 
processes  of  kyanizing  wood,  and  of  smoking  fish  and  meat,  being  familiar  ex- 
amples of  their  action.  The  complete  dessication  of  organic  substances,  or  the 
extraction  of  their  albuminous  constituents  by  steeping  in  water,  or  steam, 
accomplish  the  same  result 


*  It  is  proper  to  state,  in  this  connection,  that  the  theory  which  assumes  the  radical  na- 
ture of  proteine  is  very  strenuously  opposed  by  many  chemists,  and  especially  by  Dumas, 
•who  regards  it  as  a  product  not  pre-existing  in  albuminous  compounds,  but  as  generated 
by  the  action  of  the  alkalies  on  these  bodies. 

QUESTIONS. — Of  what  radical  are  they  supposed  to  be  derivatives  ?  What  are  the  char- 
acteristics of  proteine  ?  How  is  it  obtained  ?  What  are  the  general  properties  of  the  al- 
buminous substances  ? 


424  ORGANIC     CHEMISTRY. 

When  albuminous  substances  are  dissolved  in  caustic  alkali,  the  sulphur 
•which  they  contain  unites  with  the  alkali  to  form  a  soluble  sulphuret,  and 
the  solution  blackens  paper  moistened  with  sugar  of  lead,  In  this  way  the 
presence  of  sulphur  in  these  compounds  may  be  readily  demonstrated.  When 
an  egg  is  boiled,  the  sulphur  present  in  its  albumen  unites  with  a  little  free 
soda,  which  is  also  a  constituent  of  the  egg,  to  form  sulphuret  of  sodium, 
and  it  is  by  the  decomposition  of  this  compound  that  the  blackening  of  silver 
spoons  used  in  contact  with  boiled  eggs  is  occasioned. 

710.  Nutritive  Value  of  Vegetable  Albuminous  Con- 
stituents , — As  the  chief  proximate  constituents  of  animal  structures, 
albumen,  caseine,  and  fibrine  have  the  same  chemical  composi:ion  as  the  al- 
buminous substances  produced  in  the  vegetable  kingdom,  the  latter  are  re- 
garded as  the  special  products  provided  by  nature  for  the  nutriment  and 
support  of  animals ;  or  in  other  words,  they  are  the  vegetable  principles  out 
of  which  animal  fibers  and  tissues  are  constructed.  All  experiments  tend  to 
confirm  this  conclusion,  and  prove  that  the  value  of  a  vegetable  product  as 
an  article  of  food  is  very  nearly  in  proportion  to  the  quantity  of  albuminous 
or  nitrogenous  compounds  which  it  contains.  This  subject  will  be  further 
discussed  hereafter. 


CHAPTER     XVIII. 

NATURAL  DECOMPOSITION   OF   ORGANIC   COMPOUNDS. 

711.  So  long  as  organic  bodies  are  pervaded  by  what  is  termed  the  vital 
principle,  so  long  do  they  tend  to  maintain  their  form  and  properties  essen- 
tially unchanged ;  but  when  deprived  of  this  influence,  they  obey  the  ordi- 
nary laws  of  chemical  attraction,  and  readily  undergo  decomposition,  the  pro- 
ducts of  such  decomposition  being  mainly  the  result  of  a  separation  or  falling 
apart  of  the  complex  substances  which  characterize  the  living  structure,  and 
a  re-arrangement  of  their  particles  in  simpler  combinations.     The  nature  of 
these  changes,  which  vary  greatly  with  the  composition  of  the  bodies  con- 
cerned, and  with  the  conditions  to  which  they  are  subjected,  may  be  gener- 
ally considered  under  three  separate  heads,  viz,,  as  decay,  fermentation,  and 
putrefaction. 

712.  Decay . — When  vegetable  tissue  (wood,  leaves,  straw,  etc.)  is  ex- 
posed to  the  action  of  atmospheric  air  and  moisture,  it  absorbs  oxygen  and 


QUESTIONS.—  How  maythe  presence  of  sulphur  In  these  bodies  be  demonstrated?  What 
is  supposed  to  be  their  special  office  ?  What  is  the  proportionate  value  of  a  vegetable 
product  as  an  article  of  food  ?  What  especially  distinguishes  living  from  dead  organized 
matter?  What  change  does  vegetable  tissue  undergo  when  exposed  to  air  and  moist- 
ure? 


DECOMPOSITION   OF   ORGANIC    COMPOUNDS.      425 

undergoes  a  slow  decay,  which  has  been  termed  by  Liebig  eremacausis  (slow 
combustion).  The  changes  which  take  place  in  this  process  are  very  nearly 
the  same  as  in  the  ordinary  combustion  of  wood,  except  that  they  occur  much 
more  slowly.  In  both  cases  tho  constituents  of  the  wood,  by  the  addition 
of  oxygen  from  the  air,  are  converted  into  carbonic  acid  and  water,  and  in 
both  cases  also  the  hydrogen  is  oxydized  more  rapidly  than  the  carbon,  as 
is  shown  by  the  darker  color  which  wood  assumes  both  in  combustion  and 
decay.  Eremacausis  further  agrees  with  ordinary  combustion,  inasmuch  as 
it  can  not  take  place  without  the  access  of  air,  and  is  uniformly  attended  with 
the  evolution  of  heat,  and  sometimes  with  light— the  total  amount  of  heat 
evolved  being  undoubtedly  the  same  in  both  cases.  (§  469.) 

The  brown  or  black  matter  into  which  vegetable  tissue  is  converted  by  de- 
cay, has  received  the  general  name  of  humus,  or  vegetable  mold,  and  is  the 
substance  which  gives  to  fertile  soils  their  rich  black  or  brown  appearance. 
Humus  is  not,  however,  regarded  as  a  distinct  compound,  but  rather  as  a 
mixture  of  several  brown  substances,  which  represent  various  degrees  of  de- 
composition of  the  original  vegetable  matter.  These  substances  have  received 
the  names  of  humine,  ulmine,  humic  acid,  ulmic  acid,  geic  acid,  crenic  and 
apocrenic  acids.  The  two  latter  are  soluble  in  water,  and  are  mainly  the 
cause  of  the  deep  yellow  or  brown  colors  which  characterize  the  waters  of 
bogs  and  swamps.  The  others  are  either  entirely  insoluble,  or  soluble  only 
in  alkaline  solutions.  The  relation  which  these  substances  sustain  to  plants 
is  an  important  one,  and  their  presence  in  certain  quantity  in  every  soil  is 
essential  to  its  fertility.  From  the  products  of  their  decomposition — carbonic 
acid  and  water — plants  derive,  through  their  roots,  from  the  soil,  their  chief 
supplies  of  nutriment.  They  also  absorb  and  retain  ammonia,  another  im- 
portant element  of  vegetable  nutrition,  and  to  some  extent  have  undoubt- 
edly the  power  of  producing  it  from  the  nitrogen  of  the  atmosphere.  The 
humus  consumed  in  vegetation  and  removed  from  the  soil  in  the  substance 
of  the  crop,  may  be  again  restored  to  the  land  by  plowing  in  straw  and  ani- 
mal manures,  or  green  crops  (clover,  etc.),  or  by  the  alternation  of  plants 
which  leave  abundant  roots  in  the  soil  (fallow  plants),  with  such  as  have  few 
roots  (grains,  etc.). 

Eremacausis  is  greatly  promoted  by  heat  and  moisture,  or  the  presence  of 
the  alkalies ;  it  is,  on  the  contrary,  arrested  or  retarded  by  cold  and  dryness. 
Wood,  cordage,  etc.,  exposed  to  the  cold  of  the  Arctic  regions,  or  to  the 
dry  atmosphere  of  Egypt  will  remain  alike  for  years  unaltered. 

713.  Putrefaction  — The  decomposition  of  vegetable  tissue  when  air 
is  wholly  or  partially  excluded  from  it,  as  for  example  when  buried  in  the 


QUESTIONS.— What  is  this  change  called  ?  What  is  the  nature  of  the  change  ?  What  is 
the  immediate  product  of  the  decay  of  vegetable  tissue  called  ?  What  is  the  composition 
of  humus  ?  What  produces  the  discoloration  of  the  water  of  bogs  and  marshes  ?  What 
relation  do  these  substances  sustain  to  vegetation  ?  How  may  humus  consumed  by  vege- 
tation be  restored  to  the  soil  ?  What  is  the  nature  of  the  decomposition  which  takes 
place  in  vegetable  tissue  when  air  is  excluded  ? 


426 


ORGANIC     CHEMISTRY. 


ground,  is  essentially  different  from  that  of  eremacausis.  In  this  case  the 
constituent  elements  rearrange  themselves  mutually  into  new  products,  either 
With  or  without  the  cooperation  of  the  elements  of  water ;  the  oxygen  gradu- 
ally uniting  with  the  carbon  to  form  carbonic  acid,  which  separates  and  leaves 
as  a  residue  substances  rich  in  carbon  and  hydrogen — hydrocarbons.  It  is  in 
this  way  that  bituminous  coal,  peat,  and  brown-coal  (lignite)  have  been  formed 
from  vegetable  matter,*  and  also  the  natural  gaseous  carburets  of  hydrogen, 

viz.,    "  marsh  gas,"  obtained   by 

220.  stirring  the  mud   at  the   bottom 

of  pools  (see  Fig.  220),  and  "fire- 
damp," evolved  from  rock-strata 
in  mines.  (§  452.)  Moist  hay, 
leaves,  manure,  etc.,  when  piled 
together  in  compact  heaps  undergo 
similar  changes,  and  are  converted 
into  black,  carbonaceous  products. 
Decomposition  of  this  character 
is  termed  putrefaction,  and  is 
somewhat  analogous  to  the  change 
which  wood  undergoes  when  sub- 
jected to  dry  distillation  or  incom- 
plete combustion.  It  differs  from 

eremacausis  (or  decay),  inasmuch  as  the  latter  can  not  take  place  without 
the  free  access  of  air,  the  oxygen  of  which  is  absorbed  by  the  decaying  bodies. 
The  two  methods  of  decomposition  may,  however,  mutually  replace  each 
other,  since  all  putrifying  bodies  pass  into  the  state  of  decay  when  exposed 
freely  to  the  air ;  and  all  decaying  matters  into  that  of  putrefaction  when  air 
is  excluded. 

Nitrogenized  animal  and  vegetable  substances,  on  account  of  their  complex 
constitution,  undergo  decay  and  putrefaction  much  more  readily  than  non- 
azotized  compounds,  and  the  products  of  their  decomposition  are  essentially 
different.  Thus  the  oxygen  of  the  substance  unites  with  the  carbon  to  form 


*  Peat  is  mainly  the  product  of  the  slow  decay  of  certain  species  of  marsh  plants  under 
water.  Every  peat-bog  was  undoubtedly,  in  the  first  instance,  a  marsh  or  swamp,  which 
has  been  filled  up  and  converted  into  a  morass  by  the  annual  growth  and  decay  of  its  sur- 
face vegetation.  The  quantity  of  vegetable  meld  which  thus  accumulates  in  the  course 
of  years  is  very  great,  and  as  the  process  of  decomposition  is  slow  and  gradual,  the  aspect 
and  constitution  of  the  different  successive  layers  of  peat  vary  greatly — those  near  the  sur- 
face consisting  of  the  half  decayed  stems  of  mosses  and  of  roots,  while  those  of  older 
formation  scarcely  exhibit  any  traces  of  their  vegetable  origin,  and  in  some  instances  are 
converted  into  a  true  bituminous  coal.  In  many  countries  peat  is  extensively  used  as  fuel, 
and  furnishes  by  distillation  oily  products  analogous  to  those  obtained  by  the  distillation 
of  coaL 


QUESTIONS. — What  are  the  products  of  such  decomposition  ?  Illustrate  this.  What  is 
decomposition  of  this  character  termed?  How  does  putrefaction  differ  from  eremacau- 
sis ?  What  are  the  products  of  the  putrefaction  of  nitrogenized  substances  ? 


DECOMPOSITION   OF   ORGANIC   COMPOUNDS.      427 

carbonic  acid,  while  the  hydrogen  divides  itself  between  the  nitrogen,  the 
sulphur,  and  the  phosphorus,  and  forms  ammonia  with  sulphuretted  and  phos- 
phuretted  hydrogen.  It  is  to  the  presence  of  these  last-named  gaseous  sub- 
stances that  the  very  offensive  odors  given  off  during  the  putrefaction  of  azot- 
ized  bodies  are  to  be  mainly  ascribed. 

714.  Fermentation, — When  a  nitrogenous  substance   undergoing 
putrefaction  is  brought  in  contact,  under  favorable  circumstances  of  tempera- 
ture and  moisture,  with  a  complex  organic  body  of  small  stability,  it  is  ca- 
pable of  inducing  in  this  latter  substance,  by  the  mere  agency  of  its  presence, 
a  state  of  putrefaction  or  decomposition.     In  such  cases  the  substance  inducing 
decomposition  is  termed  a  "ferment"  and  the  decomposition  induced,  "fer- 
mentation."    For  example,  a  solution  of  pure  sugar  may  be  preserved  unal- 
tered for  any  length  of  time,  but  if  a  minute  quantity  of  putrescent  matter 
containing  nitrogen  be  added  to  it,  fermentation  at  once  takes  place,  and  the 
elements  of  the  sugar  break  up  into  alcohol  and  carbonic  acid.     "  In  the 
same  manner,  the  most  minute  portion  of  milk,  paste,  juice  of  beet-root,  flesh 
or  blood,  in  the  state  of  decomposition,  causes  fresh  milk,  paste,  juice  of  beet- 
root, flesh  or  blood,  to  pass  into  the  same  condition  when  brought  in  contact 
with  them." 

The  method  in  which  ferments  act  is  not  well  understood,  since  they  do 
not  enter  into  combination  with  the  fermenting  substance  or  with  any  of  it3 
elements.  The  theory,  however,  most  usually  adopted  is,  that  the  molecules 
of  the  ferment,  or  substance  already  undergoing  change,  are  capable  of  im- 
parting motion  to  the  molecules  of  other  substances  by  contact,  and  that 
through  the  impulse  thus  received,  the  equilibrium  of  forces  previously  exist- 
ing between  the  molecules  of  the  body  acted  on  are  overcome  and  de- 
stroyed. 

715.  Yeast. — The  substance  most  potent  in  exciting  fermentation  in 
solutions  of  sugar  is  a  species  of  microscopic  vegetation  which  is  spontaneously 
developed  in  the  organs  of  plants,  and  in  a  large  number  of  nitrogenous  sub- 
stances, when  left  to  putrify.     This  organism,  which  passes  into  a  state  of 
putrefactive  decomposition  with  great  readiness,  is  termed  yeast,  or  ferment. 
It  is  obtained  in  the  greatest  abundance  when  a  solution  of  sugar  mixed  with 
albuminous  substances  of  animal  or  vegetable  origin  is  exposed  to  the  air 
at  ordinary  temperatures. 

When  yeast  is  added  to  a  solution  of  sugar,  it  not  only  excites  fermentation, 
but  if  there  are  albuminous  substances  present,  it  occasions  the  production 
of  an  immense  additional  quantity  of  yeast.  For  example,  if  we  add  to  clear 
fresh  juice  of  ripe  grapes  a  few  particles  of  yeast,  the  liquid  will  in  a  short 
time  grow  thick  and  give  off  bubbles  of  gas,  or  ferment,  and  in  a  few  hours 
a  layer  of  grayish-yellow  yeast  will  collect  upon  its  surface.  In  the  heat  of 
the  fermentation  the  yeast  plants  are  produced  in  immense  numbers,  mil- 

QTTEBTIONS. — Explain  the  meaning  of  ferment  and  fermentation.  What  are  examples? 
What  is  the  theoretical  action  of  ferments?  What  is  yeast?  How  is  it  formed  ?  Illus- 
trate this. 


428  ORGANIC     CHEMISTRY. 

..-,  lions  of  its  minute  organisms  being  contained  in 

the  space  of  a  single  cubic  inch.  Fig.  221  repre- 
sents the  appearance  of  the  yeast  globules  under 
the  microscope,  and  the  manner  in  which  they 
propagate  by  division.  Ordinary  brewer's  yeast 
is  formed  in  this  manner  in  the  fermentation  of 
infusions  of  malt.  Artificial  yeast,  or  leaven,  may 
bo  prepared  by  exposing  a  piece  of  dough  for 
some  days  to  a  moderate  temperature,  until  it 

©    ^^^^CSDQeo  acquires  a  sour,  or  vinous  odor.     The  fermenting 

agent  in  this  case  is  the  gluten  of  the  dough  in  a 
state  of  incipient  putrefaction.  Yeast  loses  its 
power  of  exciting  fermentation  when  perfectly 
dried,  or  heated  to  a  temperature  of  212°  F.,  or  if  mixed  with  alcohol,  acids, 
or  alkalies,  and  finally  by  the  completion  of  its  own  decomposition. 

716.  Diff  e  r  ent  Kinds  of  Fermentation, — The  products  of 
fermentation  vary  under  different  circumstances.  The  conversion  of  sacchar- 
ine liquids  into  alcohol  and  carbonic  acid  is  termed  vinous,  or  alcoholic  fer- 
mentation. For  the  production  of  this  change  a  temperature  of  from  50°  to 
86°  F.  is  necessary.  Under  50°  F.  fermentation  does  not  proceed.  All 
vegetable  bodies  contain  some  substances  which  act  as  a  ferment,  and  there- 
fore, by  the  addition  of  moisture  and  regulation  of  the  temperature,  various 
kinds  of  grain  containing  starch,  and  ripe  fruits  containing  sugar,  will  un- 
dergo naturally  the  vinous  fermentation.  Thus  cider  is  formed  from  apples, 
and  beer  from  grain. 

A  liquid  which  has  already  undergone  the  vinous  or  alcoholic  fermentation, 
is  capable  of  experiencing  another  change  when  exposed  to  the  air  in- con- 
nection with  a  small  quantity  of  decomposing  azotized  matter — its  alcohol 
being  converted  into  acetic  acid  and  the  liquid  into  vinegar.  This  has  been 
called  acetous  fermentation. 

There  are  a  variety  of  substances  which,  when  added  to  fermentable 
liquids,  even  in  very  minute  quantities,  have  the  power  of  preventing  de- 
composition ;  such  are,  for  example,  the  oil  of  mustard,  sulphurous  acid,  ni- 
trous acid,  etc.  New  cider,  it  is  well  known,  is  kept  sweet  by  the  addition 
of  mustard-seed,  or  by  burning  sulphur  in  the  barrels  previous  to  filling  with 
liquor. 

When  azotized  matters  are  beginning  to'  decompose  they  are  at  first  not 
able  to  excite  the  true  alcoholic  fermentation  in  solutions  of  sugar,  but  it  is 
necessary  for  this  that  their  decomposition  should  be  tolerably  active  and  ad- 
vanced. But  even  in  the  early  stage  of  their  transformation  they  are  able  to 
effect  a  very  important  change  in  the  elements  of  sugar,  and  cause  it  to  un- 
dergo a  pecuh'ar  kind  of  fermentation,  the  result  of  which  is  the  production  of 

QTTESTIONS — How  may  artificial  yeast  be  prepared  ?  Under  what  circumstances  does 
yeast  lose  its  power  ?  "What  is  vinous  fermentation  ?  What  are  examples  ?  What  is 
acetous  fermentation  ?  What  substances  are  capable  of  arresting  fermentation  ?  Is  all 
decomposing  azotized  matter  capable  of  inducing  alcoholic  fermentation  ?  Illustrate  this. 


DECOMPOSITION   OF   ORGANIC   COMPOUNDS.      429 

an  acid  called  lactic  acid,  and  a  viscous  substance  analogous  to  sugar.  This 
fermentation,  which  has  been  termed  viscous,  or  lactic  acid  fermentation,  is 
especially  produced  when  milk  or  cheese  curd  is  mixed  with  sugar  at  a  tem- 
perature of  86°  to  94°  F.  If,  however,  the  curd  of  milk  is  in  an  advanced 
stage  of  decomposition,  it  produces  at  the  temperature  of  about  100°  F.  the 
vinous  fermentation,  and  the  sugar  is  converted  into  alcohol  and  carbonic 
acid.  In  this  way  the  Tartars  prepare  a  spirituous  liquor  from  mare's  milk, 
called  "  koumiss," 

717.  Lactic  acid  derives  its  name  from  tho  circumstance  that  it  is  the  acid 
Which  imparts  sourness  to  milk,  and  is  the  immediate  product  of  the  decom- 
position of  that  liquid.     Lactic  acid,  when  kept  in  contact  with  caseine  in  the 
first  stage  of  its  decomposition  for  some  time,  at  a  temperature  of  about  95° 
F.,  is  itself  capable  of  experiencing  a  transformation  into  a  sour,  pungent 
smelling  liquid  termed  butyric  acid,  and  the  change  in  question  is  known 
as  butyric  fermentation.     The  conversion  of  starch  into  sugar  by  the  action 
of  diastase,  is  also  regarded  as  a  species   of  fermentation,  and  is  termed 
" saccharine"     Several  other  forms  of  fermentation  in  addition  to  those  enu- 
merated, are  also  recognized,  but  the  most  important  of  them  all  are  the  al- 
coholic and  acetous. 

718.  Organic  substances  do  not  possess  the  power  of  entering  sponta- 
neously into  fermentation  and  putrefaction,  but  it  is  necessary  that  some 
change  in  the  attraction  of  their  elements  should  previously  take  place.     This 
exciting  cause  is  undoubtedly  the  oxygen  of  the  atmosphere  which  surrounds 
all  bodies,  and  we  accordingly  find  that  eremacausis  always  precedes  fermen- 
tation and  putrefaction,  and  that  it  is  not  until  after  the  absorption  of  a  cer- 
tain quantity  of  oxygen  that  tho  signs  of  a  transformation  in  the  substances 
show  themselves.     When  the  condition  of  intestine  motion  is  once  excited, 
the  presence  of  oxygen  for  the  continuance  of  the  action  is  no  longer  neces- 
sary.    The  smallest  particle  of  an  azotized  substance  in  its  act  of  decomposi- 
tion, also  propagates  this  state  of  motion  to  the  particles  of  the  substance  in 
contact  with  it,  and  although  the  air  be  afterward  entirely  excluded,  fermen- 
tation or  putrefaction  will  proceed  uninterruptedly  to  its  completion.    Animal 
food  of  every  kind,  and  even  the  most  delicate  vegetables,  may  be  preserved 
unchanged  for  years,  if  heated  to  the  temperature  of  boiling  water  in  vessels 
from  which  the  air  is  completely  excluded.     A  fresh  exposure  to  the  air  at 
any  period  will,  however,  induce  fermentation.* — LIEBIO, 


*  The  method  of  putting  up  "preserved  meats"  is  essentially  as  follows;  the  meat  is 
first  placed  in  a  tin  cylinder,  which  is  then  filled  with  a  properly  prepared  soup,  and  a 
cover,  pierced  with  a  minute  hole,  is  soldered  on  air-tight.  The  cylinder  is  next  de- 
posited in  a  bath  of  chloride  of  calcium  solution  (which  does  not  boil  under  a  temperature 
of  320 J  F.),  where  its  contents  are  subjected  to  heat  until  sufficiently  cooked.  When  this 
is  effected,  and  the  air  in  the  interior  completely  expelled  by  the  evolution  of  steam,  the 
minute  orifice  in  the  cover  is  suddenly  and  effectually  closed  with  a  drop  of  solder.  The 

QUESTIONS.— What  is  the  acid  of  sour  milk  ?  What  is  butyric  fermentation  ?  Are  there 
any  other  kinds  of  fermentation  ?  Do  organic  substances  possess  the  power  of  sponta- 
neous change  ?  What  is  necessary  to  effect  this  ?  How  may  animal  food  be  preserved  ? 


430  ORGANIC     CHEMISTRY. 

719.  Poisons,  Contagions,  Miasms  ,  —  "  When  a  chemical  agent 
or  substance  is  brought  in  contact  with  matter  endowed  with  life  (as,  for 
example,  if  it  is  introduced  into  the  stomach  or  any  other  part  of  the  animal 
organization),  it  tends  to  enter  into  combination  with  it,  and  effect  decompos- 
ition. This  tendency  is  opposed  by  the  vital  principle,  and  the  result  will 
depend  upon  the  strength  of  their  respective  actions.  If  the  chemical  element 
is  forced  to  yield  to  the  superior  power  of  the  vital  action,  it  is  digested,  and 
exercises  no  chemical  influence  upon  the  living  organ  ;  when,  however,  it  ia 
able  to  effect  a  change  in  the  operation  of  the  vital  principle,  as  in  changing  its 
direction,  strength,  or  intensity,  without  destroying  it,  it  is  said  to  act  medi- 
cinally ;  but  when  it  obtains  an  ascendancy  over  the  vital  force,  and  tends  to 
destroy  it,  it  acts  as  a  poison.  Food  will  act  as  a  poison,  that  is,  will  pro- 
duce disease,  when  it  is  able  to  exercise  a  chemical  action  by  virtue  of  its 
quantity  ;  or  when  either  its  condition  or  presence  retards,  prevents,  or  arrests 
the  motion  of  any  organ.  A  medicament  administered  in  excessive  quantity 
may  act  as  a  poison,  and  a  poison  in  small  doses,  as  a  medicament.  Thus  the 
quantity  of  a  substance  and  its  condition  must,  obviously,  completely  change 
its  chemical  influence  in  the  system." 

Some  inorganic  poisons,  such  as  arsenic,  corrosive-  sublimate,  etc,  exert  a 
destructive  action  upon  animal  life,  by  forming  with  the  component  parts  of 
the  body  compounds  which  are  not  susceptible  of  the  changes  which  it  is  the 
office  of  the  vital  principle  to  produce.  Other  inorganic  poisons,  like  cor- 
rosive acids,  destroy  at  once  the  form  and  structure  of  the  tissues  with  which 
they  are  brought  in  contact  In  both  cases  the  organs  fail  to  fulfill  their 
offices,  and  disease  or  death  ensues.  "  If  the  quantity  of  poison  is  so  small 
that  only  small  portions  of  the  body,  which  are  capable  of  being  regenerated, 
have  entered  into  combination  with  it,  then  eschars  (scabs)  are  produced, 
and  the  compounds  of  the  dead  tissues  with  the  poison  are  thrown  off  by 
the  healthy  parts."* 

cylinder  is  then  allowed  to  cool,  and  form  a  condensation  of  its  contained  vapor,  both  its 
ends  are  pressed  inward,  and  become  concave.  Thus  hermetically  sealed,  it  is  exposed  in 
a  test  chamber,  for  at  least  a  month,  to  a  temperature  above  what  it  is  ever  likely  to 
encounter  ;  from  90°  to  110°  F.  If  the  process  has  failed,  putrefaction  takes  place,  and 
gas  is  evolved,  which  will  cause  the  ends  of  the  case  to  bulge,  so  as  to  render  them  con- 
vex instead  of  concave.  But  the  contents  of  those  cases  which  stand  the  test  will  infalli- 
bly keep  perfectly  sweet  and  good  in  any  climate,  and  for  any  number  of  years.  If  there 
be  any  taint  about  the  meat  when  put  up,  it  invariably  ferments,  and  is  detected  in  tho 
proving  process. 

*  "  The  limit  at  which  substances  like  arsenic,  corrosive  sublimate,  etc.,  cease  to  act  an 
poisons,  may  be  determined  with  great  certainty  ;  for  since  their  combination  with  or- 
ganic matters  must  be  regulated  by  chemical  laws,  death  will  inevitably  result  when  the 
organ  in  contact  with  the  poison  finds  sufficient  of  it  to  unite  with  atom  for  atom,  whilst 
if  the  poison  is  present  in  smaller*  quantity,  a  part  of  the  organ  will  retain  its  vital  func- 


.—  When  a  chemical  agent  is  brought  in  contact  with  living  matter,  what 
takes  place  ?  When  will  chemical  substances  act  as  food,  as  medicine,  and  as  poison  ? 
Illustrate  how  the  quantity  and  condition  of  a  substance  may  change  its  chemical  influ- 
ence on  the  system?  How  do  inorganic  poisons  generally  produce  their  destructive 
effects? 


DECOMPOSITION  OF   ORGANIC   COMPOUNDS.      431 

With  respect  to  the  action  of  poisons  like  Prussia  acid,  strychnia,  etc.,  no 
very  satisfactory  explanation  can  be  given. 

In  addition  to  the  poisons  noticed,  "  there  is  a  class  of  substances  gener- 
ated during  certain  processes  of  decomposition,  which  act  upon  the  animal 
economy  as  deadly  poisons,  not  by  entering  into  combination  with  it,  or  by 
reason  of  their  containing  a  poisonous  principle,  but  solely  by  virtue  of  their 
peculiar  condition  ;"  in  other  words,  these  products  being  in  a  state  of  de- 
composition themselves,  act  as  ferments,  and  by  their  simple  presence  tend  to 
excite  decomposition  or  disease  in  the  animal  substances  with  which  they  are 
brought  in  contact. 

The  most  striking  illustration  of  this  principle  is  to  be  found  in  the  case 
of  the  wounds  which  physicians  sometimes  accidentally  inflict  upon  them- 
selves in  the  dissection  of  dead  bodies.  The  knife,  in  such  instances,  intro- 
duces through  the  wound  a  minute  portion  of  matter  in  the  state  of  decom- 
position or  putrefaction,  which  acts  as  a,  ferment,  and  causes  the  healthy  blood 
in  contact  with  it  to  pass  into  the  same  decomposed  state  as  itself;  the  ac- 
tion once  commenced,  extends  with  great  rapidity,  and  very  often  affects  the 
whole  body  and  produces  death — injuries  to  the  system  of  this  character  being 
almost  beyond  the  control  of  medical  treatment.  The  virus  of  the  small-pox, 
plague,  etc.,  appear  to  act  in  like  manner,  inasmuch  as  the  most  careful  ex- 
amination fails  to  extract  from  them  any  poisonous  principle.  "When  brought 
in  contact,  however,  either  directly  or  indirectly,  with  the  blood,  they  commu- 
nicate to  it  their  own  condition. 

Contagion  and  miasm,  or  miasmata,  are  generally  included  among  poisons 
of  this  class. 

We  apply  the  term  contagion  to  that  subtile  matter  which  proceeds  from  a 
diseased  person,  or  body,  and  which  communicates  disease  to  another  person 
or  body.  It  is  characterized  by  its  ability  to  reproduce  itself.  Miasm,  on  the 
other  hand,  is  the  product  of  the  decay  or  putrefaction  of  animal  or  vegetable 
substances,  and  causes  disease  without  being  itself  reproduced. 

The  nature  of  the  substances  which  constitute  contagion  and  miasm  is  not 
well  understood  ;  according  to  some  authorities,  they  are  merely  putrid  mat- 
ters, and  according  to  others,  they  are  microscopical  animals  or  plants,  which 
like  yeast,  readily  undergo  decomposition.* 


tions."  The  comparative  weight  of  an  equivalent,  or  of  an  atom  of  any  one  of  the  highly 
complex  substances  which  make  up  the  animal  organism,  is,  however,  so  exceedingly 
great,  that  a  very  small  amount  of  poison  is  sufficient  to  completely  satisfy  the  combin- 
ing affinities  of  a  very  large  quantity  of  animal  substance  ;  the  proportion  iu  the  case  of 
ft  brine  and  arsenic  being  as  6361  parts  of  the  former  to  1  of  the  latter. 

*  Very  many  curious  observations  have  been  made  upon  these  topics.  A  forest  inter- 
posed to  the  passage  of  a  current  of  moist  air  charged  with  pestilential  miasmata,  some- 
times preserves  all  behind  it  from  its  effects,  whereas  the  uncovered  portion  of  a  district  is 
exposed  to  disease.  The  trees,  in  such  cases,  appear  to  filter  the  air,  and  to  purify  it  by 

QTTESTIOKS. — What  is  known  respecting  the  action  of  poisons,  like  Prussic  acid,  etc.  ? 
What  other  class  of  poisons  are  mentioned  ?  Explain  the  manner  of  their  action.  "What 
are  included  under  this  class  ?  What  is  contagion  ?  What  is  miasm  ? 


432  ORGANIC     CHEMISTRY. 

Mildew  is  a  species  of  decomposition  occasioned  by  the  development  and 
growth  of  a  class  of  microscopic  fungi ;  (a  fungus  being  a  cellular,  flowerless 
plant).  The  dark  spots  observed  upon  awnings,  sails,  etc.,  exposed  to  the 
weather,  are  familiar  examples  of  its  action.  The  most  effectual  agent  in  pre- 
venting mildew  is  chloride  of  zinc. 

Many  of  the  poisons  which  act  as  ferments,  and  readily  excite  disease  when 
brought  in  contact  with  the  blood,  such  as  the  contagious  matter  of  small- 
pox, fevers,  etc.,  are  wholly  inoperative  when  introduced  into  the  stomach. 
The  explanation  of  this  is,  that  they  are  alkaline  or  neutral  in  their  properties, 
and  are  therefore  destroyed  or  neutralized  by  the  free  acid  which  always  ex- 
ists in  the  stomach.  Poisons  of  a  similar  character,  however,  which  have 
an  acid  reaction,  appear,  when  placed  under  the  same  circumstances,  to 
retain  all  their  frightful  properties.  The  products  of  the  incipient  putrefac- 
tion of  meat  and  fish  are  particularly  liable  to  act  in  this  manner.  In  Ger- 
many, especially,  the  effects  of  a  poison  of  this  character,  resulting  from  a 
peculiar  kind  of  putrefaction  occurring  in  sausages,  and  hence  termed  the 
"  sausage  poison,"  have  been  very  carefully  studied.  The  symptoms  which 
precede  death  in  cases  of  poisoning  by  putrefied  sausages  are  very  remark- 
able. "  There  is  a  lingering  and  gradual  wasting  of  muscular  fiber,  and  of 
all  the  constituents  of  the  body  similarly  composed ;  the  patient  becomes 
much  emaciated,  dries  to  a  complete  mummy,  and  finally  dies." 

The  flesh  of  animals  killed  when  overdriven  or  exhausted,  is  also  very 
liable  to  produce  diseases  which,  in  the  rapidity  of  their  action  and  deadly 
effect,  resemble  cholera ;  the  symptoms,  however,  do  not  generally  manifest 
themselves  until  some  little  time  has  elapsed  after  the  food  has  been  received 
into  the  stomach.  •  The  origin  of  the  poison  in  the  meat  in  these  instances 
is  explained  as  follows :  all  mental  and  physical  effort  is  accompanied  by  and 


removing  the  miasmata.  Trees  also  appear  to  prevent  miasmata  by  absorbing  it.  The 
negroes  of  the  South  plant  the  sunflower  near  their  cabins  as  a  preventative  against  fever 
and  ague.  Facts  also  show  that  malaria  does  r.ot  prevail  in  the  neighborhood  of  swamps 
surrounded  with  thick  forests— the  vicinity  of  the  Dismal  Swamp,  for  example,  being 
healthy,  while  the  marshes  of  the  adjacent  sea-board  are  most  pestilential "  Flint,  in  his 
account  of  the  Mississippi  Valley,  mentions  the  fact  that  the  wood-cutters  on  the  banks 
of  the  streams  -where  the  trees  had  been  cut  away,  were  constantly  attacked  by  malarious 
fevers,  while  such  diseases  among  the  workmen  in  the  forest  were  comparatively  rare, 
although  the  ground  on  which  they  worked  was  quite  as  moist.  Every  tree  which  they 
left  to  decay  on  the  ground  helped  to  create  the  poison,  while  every  tree  left  standing 
helped  to  absorb  it  Many  cases  might  be  cited  where  the  cutting  down  of  woods  has  had 
a  most  unfavorable  effect  upon  the  health  of  the  surrounding  region.  The  district  around 
Rome  is  only  a  celebrated  instance  of  what  is  a  very  common  experience.  Dampness  in 
not  a  source  of  miasmata,  but  decomposition  caused  by  too  rapid  drying,  whether  of  vege- 
table matter  or  animal  infusoria.  A  ditch  which  alternates  from  wet  to  dry,  or  a  pool 
which  is  weekly  emptied  and  replenished  as  wind  and  shower  follow  each  other,  gives 
forth  a  much  more  deadly  poison  than  ground  which  is  uniformly  and  steadily  satu- 
rated.1" 

QUESTIONS.— What  is  mildew  ?  What  are  characteristic  differences  of  action  in  poisons 
acting  like  ferments?  What  are  illustrations?  What  is  the  character  of  the  flesh  ot 
overdriven  animals  ? 


ALCOHOL     AND    ITS    DERIVATIVES.         433 

requires  an  expenditure  of  healthy  animal  substance.  The  brain,  for  example, 
is  undoubtedly  used  up  by  thinking,  the  muscles  by  exercise,  the  nerves  by 
excitation.  In  the  healthy  state  of  the  system,  the  waste  thus  occasioned  is 
at  once  restored,  and  the  products  of  decomposition  are  removed  by  the  or- 
gans of  secretion,  and  thrown  off  from  the  body.  If  the  functions  of  the 
organs  of  secretion  are  impeded,  the  products  of  decomposition  accumulate 
in  the  system  and  occasion  disease.  In  the  case  of  overdriven  animals,  the 
products  of  decomposition  consequent  upon  unusual  and  excessive  physical 
exertion,  remain  in  the  body,  because  the  organs  of  secretion  have  not  had 
sufficient  opportunity  to  discharge  their  office  before  the  animals  are  slaugh- 
tered. The  meat,  therefore,  is  full  of  substances  in  just  that  state  of  decom- 
position which  enables  them  to  act  most  effectually  as  ferments,  and  their 
presence,  therefore,  renders  the  flesh  of  the  most  healthy  animal  unwhole- 
some. It  should  also  be  mentioned,  that  the  most  severe  cases  of  poisoning 
of  this  character  seem  to  occur  when  the  putrefactive  fermentation  in  the 
meat  has  only  just  commenced,  and  when  its  presence  is  hardly  discernible 
by  the  senses. 

720.  Every  form  of  disease  is  occasioned  by  changes  or  transformations 
which  take  place  in  organs  in  a  manner  different  from  what  occurs  in  ordi- 
nary healthy  action.  If  these  transformations  are  perfected  'in  constituents 
of  the  body  which  are  not  essential  to  life,  without  other  parts  taking  a  share 
in  the  decomposition,  the  form  of  the  disease  is  termed  mild  or  benignant ; 
but  when  the  changes  affect  the  organs  essential  to  life,  the  disease  is  termed 
malignant. — LIEBIG. 


CHAPTER    XIX. 

ALCOHOL     AND     ITS     DERIVATIVES. 

721.  THE  term  alcohol  is  applied  by  chemists  to  a  series  of  compounds  of 
a  dissimilar  but  analogous  composition,  and  similar  properties.  They  all 
consist  of  carbon,  hydrogen,  and  oxygen,  are  all  liquid  at  ordinary  tempera- 
tures, and  are  characterized  by  possessing  a  high  degree  of  volatility  and  a 
pungent  taste  and  smell.  The  most  important  of  the  alcohols  are  wine  alco- 
hol, C4H602,  methylic  alcohol,  C2H402,  and  amylic  alcohol,  Ci0Hi202.  The 
term  alcohol,  however,  in  its  ordinary  acceptation,  refers  solely  to  the  spirit- 
uous principle  resulting  from  the  fermentation  of  saccharine  bodies. 

Sugar  is  the  only  substance  susceptible  of  vinous  fermentation,  and  the 
only  substance  from  which  alcohol  can  be  derived.  Potatoes,  the  cereal 

QUESTIONS.— Why  is  it  liable  to  induce  disease?  What  is  the  occasion  of  all  disease? 
When  is  disease  said  to  be  benignant  and  when  malignant  ?  What  is  the  chemical  signi- 
fication of  the  term  alcohol?  What  is  its  ordinary  meaning?  From  what  substances 
only  can  alcohol  be  produced  ?  How  do  we  produce  alcohol  from  bodies  which  consist 
mainly  of  starch? 

19 


434 


ORGANIC    CHEMISTRY. 


grains,  and  other  vegetable  products  deficient  in  sugar  from  which  alcohol  is 
obtained,  are  rendered  available  for  this  purpose  by  first  converting  their 
starch  into  sugar.  The  various  kinds  of  liquors  prepared  by  means  of  fermen- 
tation, may  be  conveniently  divided  into  two  classes — the  fceers,  produced  from 
the  nutritive  and  starch  containing  grains  and  roots,  and  the  wines  produced 
from  the  juices  of  fruits  which  contain  sugar. 

722.  T  h  e  Beers . — "When  a  solution  of  grape  sugar  is  dissolved  in 
water,  and  a  little  yeast  added,  fermentation  speedily  ensues,  and  the  sugar 
breaks  up  into  alcohol,  water,  and  carbonic  acid ;  of  these  several  bodies,  the 
two  former  remain  in  the  liquid,  while  the  latter  escapes  as  bubbles  of  gas 
into  the  air.*  "When  cane  sugar  is  used  the  results  are  the  same,  the  yeast, 
however,  in  the  first  instance  effecting  a  transformation  of  the  cane  sugar  into 
grape  sugar.  For  the  completion  of  these  changes  it  is  not  necessary  that  air 
should  be  present. 

When  the  cereal  grains,  etc.,  are  used  for  the  manufacture  of  alcohol,  the 
first  step,  as  has  been  already  stated,  consists  in  effecting  a  change  of  the 
starch  into  this  sugar.  This  transformation  may  be  brought  about  by  the 
action  of  dilute  sulphuric  acid,  but  in  practical  operations  this  agent  is  rarely 
used,  and  the  change  is  effected  through  the  influence  of  diastase  (§  688). 
In  order  to  arrive  at  a  clear  understanding  of  this  phenomenon,  it  is  neces- 
sary to  first  consider  the  conditions  under  which  diastase  originates. 

A  seed  or  grain  consists  essentially,  in  the  first  instance,  of  two  substances, 
FIG.  222.  starch  and  gluten,  in  which  is  contained  a  little  rudi- 

mentary plantlet,  called  the  germ  or  embryo.     It  is  for 
the  nourishment  and  support  of  this  embryo,  before  it 
has  attained  sufficient  development  to  be  able  to  derive 
its  own  sustenance  from  the  soil  or  air,       -piG.  223. 
that  the  supplies  of  starch  and  gluten  con- 
tained in  the  seed  are  provided.  Fig.  222 
represents  a  grain  of  Indian  corn,  divided  so  as  to  show  the  em- 
bryo embedded  in  the  starch  and  gluten,  which  make  up  the 
bulk  of  the  seed.     Fig.  223  represents,  in  like  manner,  a  sec- 
tion of  an  acorn.     Under  the  joint  influence  of  heat  and  mois- 
ture, the  embryo  of  the  seed  begins  to  sprout,  or  germinate, 


This  decomposition  may  be  represented  as  follows  :— 

C         H        O 

One  atom  of  grape  sugar  =  12 _^4 14 

Two  of  alcohol  ="8        12""     4 

Four  of  carbonic  acid        =4          0          8 

Two  of  water  =    022 

Total,  12        14        14 

The  yeast,  which  occasions  the  decomposition,  takes  no  part  in  any  of  the  combinations 
resulting. 

QUESTIONS.— When  yeast  is  added  to  a  solution  of  grape  sugar,  what  takes  place? 
What  in  the  case  of  cane  sugar  ?  How  is  starch  changed  into  sugar  preliminary  to  the 
manufacture  of  alcohol  ?  Of  what  does  a  seed  consist  ? 


ALCOHOL    AND    ITS    DERIVATIVES.        435 

and  puts  forth  a  tiny  stem  or  axis,  bearing  upon  its  summit  a  FlG.  224. 
pair  of  small  leaves.  It  has  now  only  to  form  a  root  by  which 
to  fix  itself  to  the  ground,  to  render  it  a  perfect,  though  dim- 
inutive plant,  capable  of  providing  for  itself.  (Fig.  224  repre- 
sents a  grain  of  Indian  corn  in  the  process  of  germination.) 
This  root  is  and  can  only  be  formed  from  the  starch  and  glu- 
ten contained  in  the  seed  j  "  but  as  both  these  substances  are 
insoluble  in  water,  they  can  not,  in  their  natural  state,  pass  on- 
wards from  the  body  of  the  seed  to  supply  the  wants  of  the 
growing  germ.  It  has  been  beautifully  provided,  therefore,  that 
both  of  them  should  undergo  chemical  changes  as  the  sprout- 
ing proceeds,  and  these  changes  take  place  at  the  base  of  the 
germ,  exactly  where  and  when  they  are  wanted  for  the  forma- 
tion of  the  root."  The  gluten  is  accordingly  first  changed  into 
diastase,  and  this  acting  upon  the  starch  converts  it  wholly 
into  grape  sugar. 

Now  the  brewer,  in  the  manufacture  of  spirituous  liquors 
from  grains,  avails  himself  of  this  natural  transformation  in  order 
to  obtain  the  sugar,  which  alone  is  susceptible  of  vinous  fer- 
mentation. The  grain  most  usually  selected  for  transformation 
is  barley,  which  is  first  moistened  in  heaps,  and  spread  upon  the  floor  of  a 
dark  room  to  heat  and  sprout.  When  "the  germination  has  advanced  te  just 
the  extent  sufficient  to  convert  the  greater  part  of  the  starch  into  sugar,  and 
the  gluten  into  diastase,  the  action  is  arrested  by  heating  the  grain  in  a  sort 
of  kiln,  which  at  once  destroys  the  vitality  of  the  germ.  The  necessity  of 
thus  violently  arresting  the  progress  of  germination,  grows  out  of  the  fact  that 
the  sugar  would  be  wholly  consumed  by  its  continuance  and  converted  into 
vegetable  tissue.  Barley  thus  treated  is  termed  malt. 

The  next  step  of  the  process  consists  in  bruising  the  malt,  and  digesting  it 
with  water,  gently  warmed,  in  what  is  called  the  "  mash-tub."  The  solution 
obtained  contains  sugar  and  diastase,  and  is  termed  wort.  By  standing  a  lit- 
tle time,  the  diastase  acts  upon  any  starch  yet  remaining  in  the  seed,  and  con- 
verts it  into  sugar ;  and  it  is  also  capable  of  changing,  in  a  like  manner,  any 
unmalted  grain  or  starch  which  may  be  added  to  the  wort  at  this  stage  of  the 
process. 

The  change  of  all  the  starch  into  sugar  being  effected,  the  wort  is  next 
heated  to  boiling,  which  destroys  any  further  action  of  the  diastase.  At  this 
point,  also,  hops  are  introduced  into  the  wort,  which,  besides  imparting  a  pe- 
culiar bitterness  and  aroma  to  the  liquid,  help  to  clarify  it.  The  boiled  liquor, 
filtered  and  clarified,  is  next  run  off  into  shallow  vessels,  and  cooled  to  a  tem- 

QTTESTIONS. — What  takes  place  in  germination?  How  does  the  brewer  avail  himself  of 
the  natural  transformation  of  the, starch  and  gluten  of  seeds?  What  is  malt?  What  is 
the  first  step  of  the  process  of  brewing  ?  What  is  the  second  ?  How  is  fermentation  ef- 
fected? How  is  fermentation  arrested  ?  Is  the  sugar  contained  in  the  wort  allowed  to 
entirely  decompose  ? 


436  ORGANIC     CHEMISTRY, 

perature  of  about  60°  F.  Teast  is  then  added,  and  fermentation  allowed  to 
proceed.  "In  a  few  hours  bubbles  of  gas  will  be  seen  rising  from  all  parts  of 
the  liquid,  a  ring  of  froth  forming  at  first  round  its  edge,  and  gradually  in- 
creasing and  spreading  until  it  meets  in  the  center,  or  until  the  whole  surface 
becomes  covered  with  a  white,  creamy  foam  of  yeast  The  bubbles  of  gas 
then  rise  and  break  in  such  numbers  that  they  emit  a  low,  hissing  sound, 
while  the  yeast  gradually  continues  to  increase  in  thickness,  and  at  last  forms 
a  tough,  viscid  crust,  which  the  brewer  skims  off  and  removes  as  soon  as  he 
judges  that  the  fermentation  is  complete,  (the  period  of  time  varying  from  six 
to  eight  days)." 

In  practice,  the  fermentation  is  always  checked  before  the  whole  of  the 
sugar  is  converted  into  alcohol,  since,  if  perfect  decomposition  were  effected, 
the  beer  would  not  keep,  but  would  soon  turn  sour  in  the  cask.  The  residue 
of  undecomposed  sugar  also  imparts  a  sweet,  pleasant  flavor  to  the  beer. 

The  liquor  is  next  drawn  off  into  casks,  where  it  undergoes  a  second  fermen- 
tation, far  more  slow  and  protracted,  however,  than  the  first ;  this  effects  what 
is  called  a  ripening  of  the  beer,  and  is  essential  to  its  preservation.  At  the  con- 
clusion of  this  second  fermentation,  the  liquors  must  be  kept  tightly  bunged, 
or  corked  up,  since,  as  soon  as  the  fermentation  ceases,  and  air  gets  access  to 
the  liquor,  oxydation  commences,  and  induces  acetous  fermentation.  The 
sparkle  and  foam  of  bottled  liquors  is  owing  to  the  carbonic  acid  gas  which  is 
generated  in  this  second  fermentation,  and  becomes  dissolved  in  the  liquors 
under  pressure. 

The  varieties  of  beer  depend  both  upon  the  difference  in  their  material  and 
the  different  management  in  their  production.  The  difference  in  the  colors 
of  ale  and  porter  depends  upon  the  color  of  the  malt  employed,  which,  in 
turn,  is  regulated  by  the  length  of  time  the  malt  is  subjected  to  the  heat  in 
the  kilns. 

723.  Lager  Beer . — Ordinary  beers,  even  after  the  second  fermenta- 
tion, contain  a  considerable  quantity  of  albuminous  or  glutinous  matter, 
which  tends  to  decompose  by  contact  with  the  air,  and  convert  the  alcohol 
into  acid  (vinegar).  Such  liquors,  therefore,  are  with  difficulty  preserved  for 
a  great  length  of  time.  In  the  preparation  of  lager,  or  Bavarian  beer,  the 
wort  is  fermented  very  slowly,  and  at  an  extremely  low  temperature,  in  large 
open  vessels;  by  which  procedure  the  yeast  produced,  instead  of  rising  at  the 
top  of  the  liquor,  falls  to  the  bottom,  and  a  separation  from  the  liquor  of  almost 
every  trace  of  nitrogenized  matters  is  at  the  same  time  effected.  The  fer- 
mentation thus  carried  on  is  very  complete,  and  continues  for  weeks,  or  even 
months ;  the  liquor  produced  being  as  clear  as  champagne,  and  richly  charged 
with  carbonic  acid.  It  may  also  be  preserved  for  years  without  becoming 
sour.  Lager  beer  derives  its  name  from  the  long  time  it  is  allowed  to  lay 
(lager)  in  vats  or  casks,  in  cool  cellars,  previous  to  consumption. 

QUESTIONS.— Does  any  further  fermentation  take  place  ?  What  occasions  the  sparkle 
and  foam  of  bottled  liquors  ?  What  occasions  the  differences  in  beer  ?  What  is  "  iager" 
beer?  How  is  it  produced  ?  What  is  the  origin  of  its  name  ? 


ALCOHOL    AND     ITS     DEKIVATIVES.         437 

724.  The  intoxicating  properties  of  malt  liquors  depend  entirely  upon  the 
alcohol  they  contain.  Of  this,  there  is  present  in  the  stronger  varieties  of 
ales  and  beers  (English  ale,  Albany  ale,  etc.),  from  5|-  to  10  per  cent,  by 
weight;  in  porter  and  "brown  stout,"  from  3$  to  6£;  in  lager  beer,  from  2 
to  3 '5  per  cent.  In  addition  to  alcohol,  the  malt  liquors  all  contain  a  certain 
quantitity  of  nutritive  matters,  consisting  of  undecomposed  sugars,  nitrogenized 
substances,  oils,  the  aromatic  parts  of  the  hop,  and  certain  mineral  salts.  In 
ordinary  strong  beers,  the  quantity  of  these  substances  varies  from  4  to  8  per 
cent,  of  the  entire  weight ;  in  some  of  the  German  beers  the  per  centage  is 
much  greater;  so  that  beer  is,  to  a  considerable  extent,  food  as  well  as 
drink. 

125.  Wines . — The  expressed  juices  of  ripe  fruits  containing  sugar,  con- 
tain also  a  peculiar  azotized  matter,  which  causes  them  to  readily  undergo  fer- 
mentation without  the  addition  of  yeast.  In  ordinary  summer  weather,  the 
clearest  juice  of  the  grape  will  enter  into  fermentation  within  a  half  an  hour 
after  its  expression,  and  give  off  bubbles  of  gas.  The  azotized  matter  which 
occasions  this  fermentation  will  not,  however,  enter  into  an  active  state  of  de- 
composition, unless  free  oxygen  has  access  to  it.  "  Consequently,  whole 
grapes,  or  those  in  which  the  skins  remain  perfect  and  entire,  may  be  dried 
and  converted  into  raisins ;  but  if  the  skin  is  once  injured,  a  little  air  gets  in, 
and  fermentation  soon  commences." 

The  method  of  making  wine  is  essentially  as  follows :  the  grapes  are  col- 
lected and  pressed;  the  juice,  which  is  called  must,  is  poured  into  vats  situ- 
ated in  cellars,  where,  as  the  temperature  is  low,  the  fermentation  proceeds  so 
slowly,  that  it  is  not  completed  until  after  some  months.  During  the  fermen- 
tation, the  impurities  rise  to  the  surface  in  the  form  of  froth,  or  yeast,  or  set- 
tle to  the  bottom  of  the  vats  (lees),  so  that  the  pure  wine  is  finally  drawn  off 
clear,  and  ready  for  use.  Wines  intended  to  be  sparkling  or  effervescing,  are 
bottled  before  the  fermentation  is  quite  finished,  so  that  the  carbonic  acid 
subsequently  evolved  remains  stored  up  in  the  liquid. 

726.  The  popular  qualities  by  which  wines  are  known,  are  their  strength, 
sweetness,  acidity,  and  flavor. 

The  strength  of  wine  depends  upon  the  alcohol  it  contains,  the  percentage 
of  which  varies  greatly  in  different  wines.  The  weaker  hocks  and  sour 
wines  contain  about  9  per  cent. ;  champagne  from  5  to  15  ;  claret  from  9  to 
15 ;  while  the  stronger  madeiras,  sherries,  and  ports,  contain  from  18  to  24 
per  cent.  The  sweetness  and  fruity  character  of  wines  is  due  to  a  portion 
of  grape  sugar  which  has  escaped  the  decomposing  action  of  the  fermentation. 
Of  this,  there  is  no  sensible  quantity  present  in  clarets,  Burgundies,  hocks, 

QUESTIONS. — To  what  are  the  intoxicating  properties  of  malt  liquors  due  ?  How  much, 
alcohol  do  they  contain  on  an  average  ?  What  other  substances  beside  alcohol  are  con- 
tained in  malt  liquors  ?  Is  it  necessary  to  add  yeast  to  the  expressed  juice  of  ripe  fruits 
to  excite  fermentation  ?  Why  do  not  grapes  ferment  upon  the  vines  ?  How  is  wine  manu- 
factured ?  How  are  sparkling  wines  prepared  ?  Upon  what  does  the  strength  of  wine 
depend?  State  the  proportion  of  alcohol  in  various  wines.  Upon  what  does  the  sweet- 
ness of  wines  depend? 


438  ORGANIC    CHEMISTRY. 

etc.  Sherries  contain  from  9  to  12  grains  of  sugar  in  an  ounce ;  ports  from 
16  to  30 ;  and  the  so-called  sweet  wines  (Cyprus,  Malmsey,  etc.)  from  60  to 
100  grains.  Some  wines,  like  champagne,  are  artificially  sweetened. 

All  wines,  malt  liquors,  and  ciders,  contain  before  undergoing  acetous  fer- 
mentation a  variable  proportion  of  free  acid,  which  imparts  to  them  a  more  or 
less  distinctly  sour  taste ;  but  in  each  liquor  the  characteristic  acid  is  differ- 
ent. Thus,  malt  liquors  contain  acetic  acid ;  ciders  and  the  liquors  allied  to 
it,  lactic  acid ;  while  the  acidity  of  wines  is  due  to  tartaric  acid.  In  all  of 
them  acetic  acid  is  also  present  in  greater  or  less  quantity,  as  it  is  always 
produced  when  the  fermentation  of  alcoholic  liquors  is  allowed  to  proceed 
too  far ;  but  lactic  acid  is  not  found  in  malt  beer  or  grape  wine  in  sensible 
quantity ;  nor  is  tartaric  acid  found  in  beer  or  cider.  When  the  fermented 
juice  of  the  grape  is  left  at  rest,  the  tartaric  acid  gradually  separates  from  it, 
and  in  combination  with  potash  deposits  itself  as  a  crust  upon  the  sides  of 
the  cask  or  bottles  (cream  of  tartar).  Hence  by  long  keeping  good  wines 
become  less  acid,  and  every  year  added  to  their  age  increases  in  proportion 
their  marketable  value.  Of  the  common  wines,  sherry  is  the  least  acid,  and 
.  the  Rhine  wines  of  Germany  the  most  so. — JOHNSON. 

The  agreeable  vinous  odor  of  wine  is  due  to  the  presence  of  a  fragrant 
ethereal  substance  called  mnanthic  ether.  This  body  does  not  exist  in  the 
juice  of  the  grape,  but  is  produced  during  fermentation,  and  may  be  isolated 
in  the  form  of  a  fetid,  highly  fluid  compound  of  carbon,  hydrogen,  and 
oxygen.  In  addition,  however,  to  this  substance,  all  wines  contain  certain 
fragrant  principles  which  impart  to  them  a  peculiar  bouquet,  or  flavor,  and 
render  wine  so  different  and  so  preferable  to  beer,  or  any  artificial  mixture 
of  spirit,  sugar  and  water.  They  exist  in  wine  in  very  minute  quantities,  and 
their  chemical  composition  is  not  well  understood.* 

In  addition  to  the  substances  mentioned,  all  wines  contain  small  quantities 
of  other  vegetable  acids,  together  with  various  coloring,  oily,  and  albuminous 
compounds. 

727.  Ardent  Spirits  , — When  fermented  liquors  are  subjected  to  a 
moderate  heat,  the  alcohol  which  they  contain,  by  reason  of  its  greater  vola- 
tility, separates  from  the  water,  and  together  with  a  little  steam  and  some 
odoriferous  substances,  rises  as  vapor.  When  this  operation  is  conducted  in 


*  Some  of  these  peculiar  bouquets  are  only  developed  by  age,  a  fact  which  the  wine 
fancier  so  well  appreciates,  that  he  will  give  many  times  the  original  price  for  a  kept  wine, 
and  millions  of  gallons  are  retained  as  stock  in  Europe  because  of  this  property.  In  ad- 
dition, wines  of  peculiar  localities  contain  special  bouquets  which  the  art  of  the  chemist 
entirely  fails  to  account  for.  Thus  the  celebrated  wine  of  Johannisberg  (the  most  costly 
of  all  wines  by  reason  of  its  flavor)  is  only  produced  upon  one  estate  in  Germany.  The 
wines  of  the  neighboring  valleys,  when  subjected  to  analysis,  show  the  same  quantities  of 
acid,  sugar,  and  alcohol,  but  they  do  not  possess  the  same  bouquet. 

QUESTIONS.—  What  are  the  sweetest  wines?  What  is  said  of  the  acidity  of  fermented 
liquors  in  general  ?  What  is  the  acid  principle  of  wine  ?  Why  do  wines  acquire  sweet- 
ness by  age?  To  what  is  the  vinous  odor  of  wine  due  ?  What  is  said  of  the  bouquet  of 
wines  ?  What  are  ardent  spirits  ? 


ALCOHOL     AND     ITS     DERIVATIVES.         439 

close  vessels  (retorts),  and  the  evolved  vapors  are  collected  and  condensed  by 
cooling  (see  Fig.  225),  liquors  containing  a  large  percentage  of  alcohol  are 
obtained.     To  such  products  of  distilla- 
tion only  is  the  term  ardent  spirits  prop-  FlG*  225' 
erly  applied. 

Every  different  fermented  liquor,  when 
distilled,  yields  an  ardent  spirit  which  is 
characterized  by  a  peculiar  flavor,  and  is 
distinguished  by  a  name  of  its  own. 
Thus,  brandy  is  the  product  obtained  by 
the  distillation  of  wine,  and  rum  the  pro- 
duct of  distilling  fermented  molasses. 
Whiskey  is  manufactured  from  corn,  rye, 
or  potatoes  in  the  following  manner :  the 
grain  or  potatoes,  boiled  or  mashed,  are 
mixed  with  a  portion  of  barley-malt  and  warm  water  to  form  a  paste,  which 
is  allowed  to  stand  for  a  time  at  an  elevated  temperature.  Under  these  con- 
ditions the  diastase  of  the  malt  converts  the  starch  into  sugar,  which  is  then 
fermented  in  the  usual  manner  by  the  addition  of  yeast.  When  the  fer- 
mentation is  concluded,  the  mass  is  placed  in  a  still,  and  the  spirituous  prin- 
ciple distilled  over  by  heat.  The  condensed  product  is  whiskey,  while  the 
residue  left  in  the  still,  called  slops,  or  swill,  is  used  as  food  for  hogs  and 
cows.*  Gin  is  prepared  by  rectifying  (redistilling)  the  spirit  obtained  from  a 
mixture  of  fermented  rye  and  barley  with  juniper  berries.  By  this  means  it 
loses  the  crude  flavor  it  originally  had,  and  acquires  the  agreeable  one  of 
junipers. 

The  percentage  of  absolute  alcohol  contained  in  ardent  spirits  intended  for 
consumption  (i.  e.,  strong  brandy,  rum,  whiskey,  etc.)  varies  from  50  to  70 
per  cent.  When  these  are  submitted  to  distillation,  a  stronger  liquor,  called 
spirits  of  wine,  is  obtained.  The  product  of  the  redistillation  of  this  last  is 
called  rectified  spirits  of  wine,  or  rectified  alcohol,  and  contains  about  90  per 
cent,  of  alcohol  and  the  balance  water.  It  is  the  strongest  alcohol  known  in 
commerce.  The  quantity  of  water  remaining  in  rectified  spirits  of  wine  can 
not  be  separated  by  simple  distillation,  but  is  accomplished  by  mixing  the 
spirits  of  wine  with  chloride  of  calcium,  or  some  other  substance  which  has 
so  strong  an  affinity  for  water  that  it  absorbs  it,  and  allows  the  alcohol  to 
distil  over  pure.  In  this  condition  the  alcohol  is  termed  absolute,  or  anhy- 
drous. Proof  spirit  is  a  mixture  of  equal  parts  of  water  and  alcohol. 


*  The  milk  yielded  by  cows  fed  on  this  refuse  is  considered  unhealthy,  and  is  popularly 
called  "swill  milk." 


QUESTIONS. — Is  the  distillate  of  all  fermented  liquors  the  same  ?  What  is  brandy.? 
What  is  rum?  How  and  from  what  is  whiskey  manufactured?  What  is  gin  ?  What  is 
the  percentage  of  alcohol  in  ardent  spirits  ?  What  are  spirits  of  wine  ?  What  is  rectified 
alcohol  ?  What  is  pure  alcohol  called  ?  How  is  it  prepared  ?  What  is  proof  spirit  ? 


440 


ORGANIC     CHEMISTRY. 


It  was  formerly  the  custom  to  estimate  the  strength  of  an  alcoholic  liqnor 
by  igniting  a  little  of  it  in  connection  with  gunpowder  j  if  the  powder  was 
fired,  the  spirit  was  considered  strong,  and  called  proof;  if,  on  the  contraryr 
it  contained  more  than  half  water,  the  powder  was  not  ignited,  and  the  spirit 
was  said  to  be  below  proof.  The  quantity  of  alcohol  contained  in  a  solution 
is  now,  however,  calculated  by  determining  its  specific  gravity  (§  40),  or 
more  conveniently  by  means  of  the  alcoholometer  (see 
Tig.  226),  which  is  so  weighted  and  graduated  that  it 
sinks  to  the  topmost  point  of  the  scale  A,  which  is 
marked  100°,  in  absolute  alcohol,  and  to  the  lowest 
degree  in  pure  water,  which  is  marked  1° — interme- 
diate positions  indicating  proportional  mixtures  of  the 
two  liquids. 

728.  Properties  of  Alcohol, — Pure,  or 
strong  alcohol,  is  a  highly  volatile,  mobile  liquid,  about 
one  fifth  lighter  than  water  (sp.  g.  0'795)  possessing 
an  agreeable,  penetrating  odor,  and  a  hot,  burning 
taste.  It  is  very  combustible,  and  burns  with  a  pale 
blue  flame  without  smoke,  but  with  intense  heat.  It 
has  a  strong  affinity  for  water,  and  absorbs  or  extracts 
it  from  substances  with  which  it  is  brought  in  contact. 
On  this  account,  taken  in  connection  with  its  property 
of  coagulating  or  hardening  albumen,  it  acts  as  a  pow- 
erful antiseptic,  and  is  much  used  to  preserve  organic  substances  from  putre- 
iaction.  Strong  alcohol  has  never  been  frozen.*  "When  taken  into  the 
Btomach  it  acts  as  a  deadly  poison,  but  when  largely  diluted  with  water  it  is, 
as  is  well  known,  stimulating  and  intoxicating.  The  solvent  powers  of  alco- 
hol are  very  great ;  it  dissolves  a  great  number  of  organic  substances  which 
are  insoluble  in  water,  such  as  the  volatile  oils  and  the  resins,  together  with 
many  acids,  salts,  the  caustic  alkalies,  and  other  substances.  Alcoholic  ex- 
tracts of  medicinal  plants,  roots,  barks,  etc.,  constitute  the  tinctures  of  phar- 
macy, and  most  of  the  liquid  perfumes  (eau  de  Cologne,  etc.)  are  solutions  of 
fragrant  and  volatile  oils  in  alcohol.  Many  varnishes,  also,  are  formed  by 
dissolving  resins  in  alcohol. 

729.  Bread . — The  preparation  of  bread  is  properly  considered  in  con- 
nection with  the  subject  of  vinous  fermentation : — 

The  flour  of  wheat  and  other  grains  which  enter  into  the  composition  of 
bread,  consists  mainly  of  starch,  gluten,  and  water,  together  with  small  pro- 


*  M.  Despretz  of  Paris,  in  1849,  succeeded,  by  the  rapid  evaporation  of  liquid  protoxyd 
of  nitrogen  and  solidified  carbonic  acid,  in  producing  a  degree  of  cold  sufficient  to  deprive 
alcohol  in  part  of  its  transparency,  and  render  it  thick  and  viscid. 


QUESTIONS. — How  is  the  quantity  of  alcohol  in  a  liquor  determined  ?  What  are  the 
properties  of  alcohol  ?  What  is  said  of  its  solvent  powers?  What  are  tinctures?  How 
are  liquid  perfumes  generally  prepared  ?  What  is  the  composition  of  flour  ? 


ALCOHOL    AND    ITS    D  E  K  I  VA  T  I VE  S.        441 

portions  of  sugar  and  gum.*  The  first  step  in  the  process  of  bread-making,  is 
to  mix  together,  in  a  suitable  vessel,  a  proper  proportion  of  flour,  yeast,  warm 
water,  and  common  salt.  This  mixture,  which  is  called  the  sponge,  is  worked 
up  to  the  consistence  of  stiff  batter,  and  then  left  for  a  few  hours  in  a  warm 
atmosphere,  during  which  time  the  yeast  excites  fermentation  in  the  sugar, 
and  occasions  its  conversion  into  alcohol  and  carbonic  acid.  The  gas  thus 
generated  does  not  escape  in  bubbles,  but  is  retained  by  the  tenacious  and 
Viscid  dough,  which,  in  consequence,  becomes  light  and  porous,  and  swells  up 
to  about  twice  its  original  size. 

"When  the  fermentation  has  proceeded  sufficiently  far,  about  twice  as  much 
flour  as  was  originally  taken  is  added  to  the  sponge,  and  the  two  are  care- 
fully kneaded  together.  This  is  a  very  laborious  part  of  the  operation,  but  is 
quite  essential  to  the  success  of  the  process,  since,  if  it  is  not  very  thoroughly 
attended  to,  the  half-fermented  sponge  will  not  be  equally  and  uniformly  dis- 
tributed throughout  the  whole  of  the  dough. 

If  the  dough  be  now  put  into  a  hot  oven,  the  fermentation  is  at  first  increased 
and  the  size  and  porosity  of  the  loaf  are  also  greatly  augmented  by  the  ex- 
pansion of  the  carbonic  acid  gas  contained  in  its  cellular  spaces.  When, 
however,  the  whole  has  been  heated  to  nearly  the  temperature  of  boiling 
water,  the  fermentation  is  suddenly  arrested ;  and  the  alcohol  and  a  large 
proportion  of  the  water  employed  in  mixing  the  dough,  being  at  the  same 
time  volatilized  by  the  heat,  the  cellular  portions  of  the  baked  bread  ac- 


*  Flint- wheat  contains,  on  an  average,  about  56  parts  of  starch,  14  of  gluten,  8  of  sugar, 
6  of  gum,  2  of  bran,  and  from  10  to  13  parts  of  water.  The  manner  in  which  the  bran,  the 
gluten,  and  the  starch  are  respectively  distributed  pIQ  227. 

throughout  the  cereal  grains,  is  shown  by  the  fol-  c~>ro  cc?  O  c?  o 

lowing  section  of  a  fully-ripe  grain  of  rye,  highly 
magnified.  (See  Fig.  227.)  a  represents  the  outer- 
Beed  coat,  consisting  of  three  rows  of  thick-walled 
cells ;  6,the  inner  seed  coat,  composed  of  a  single  layer 
of  thick- walled  cells,  having  scarcely  any  cavity  ;  c, 
a  layer  of  cells  containing  gluten.  These  three  to- 
gether form  the  bran,  d  represents  the  cells  con- 
taining starch  grains  in  the  interior  of  the  seed. 
The  outer  coating  of  the  seed  contains  only  3  or  4 
per  cent,  of  gluten,  while  the  inner  coating  contains  from  14  to  20  per  cent.  All  this  is 
separated  in  the  bran.  In  addition  to  this,  however,  gluten  is  diffused  everywhere  through- 
out the  mass  of  grain,  among  the  cells  containing  starch.  As  the  nutritive  quality  of  any 
Variety  of  grain  depends  very  much  upon  the  proportion  of  gluten  which  it  contains,  and 
as  the  bran  embodies  a  larger  proportion  of  this  substance  than  the  white  part  of  the  flour, 
it  is  obvious,  that  by  sifting  out  the  bran,  as  is  usually  done,  we  render  the  flour  less  nu- 
tritious. The  bran  generally  constitutes  about  one  fourth  part  of  the  whole  weight  of  the 
grain.  When  wheat  is  burned,  there  is  left  about  2  per  cent,  ash,  nearly  one  half  of  which 
consists  of  phosphoric  acid :  the  other  constituents  being  mainly  potash,  silica,  magnesia, 
soda,  oxyd  of  iron,  etc.  These  mineral  ingredients  are  unequally  diffused  throughout 
the  seed ;  fine  flour  containing  the  smallest  proportion,  and  the  bran  the  most. 

QUESTIONS.— What  is  the  first  step  in  the  process  of  bread-making?  What  is  the  ne- 
cessity of  producing  fermentation  in  dough  of  bread?  What  is  the  second  stage  of  the 
process  ?  What  occurs  in  the  baking  ? 

19* 


442  ORGANIC     CHEMISTRY. 

quire  so  much  solidity,  that  they  retain  their  form  and  structure  permanently. 
If,  however,  the  heat  of  the  oven  is  not  properly  regulated,  or  if  the  dough 
contains  too  much  water,  the  cellular  portions  harden  too  slowly,  and  on  the 
escape  of  the  carbonic  acid,  collapse  and  run  together  (slack-baking).  The 
alcohol  which  escapes  from  the  bread  in  baking  may,  by  means  of  a  proper 
apparatus,  be  collected  and  condensed  into  spirits,  and  this,  in  fact-,  is  done  in 
Borne  of  the  European  bakeries, 

The  yeast,  in  converting  the  sugar  of  the  flour  into  alcohol  and  carbonic 
acid,  acts  also  upon  the  starch,  in  the  manner  of  diastase,  and  transforms  .*. 
portion  of  it  into  sugar ;  so  that,  although  the  sugar,  which  originally  existed 
in  the  flour,  is  almost  completely  decomposed,  the  amount  present  in  the 
bread  remains  very  nearly  constant.  "It  is  sometimes  stated,  that,  by  the 
ordinary  mode  of  bread-making,  a  large  portion  of  the  most  valuable  part  of 
flour  is  destroyed  by  fermentation.  This,  however,  is  not  the  case.  Very 
little  of  the  azotized  matter  of  the  flour  is  lost  during  the  fermentation  of  the 
dough :  the  chief  effect  produced  is  a  loss  of  a  portion  of  the  sugar ;  but  as 
nearly  an  equal  quantity  is  formed  from  the  starch,  the  real  e fleet  of  the  fer- 
mentation may  be  said  to  be  principally  the  loss  of  about  5  per  cent,  of  starch." 
— SOLLY. 

The  addition  of  common  salt  to  bread  renders  it  more  wholesome  and  di- 
gestible, and  also  assists  in  its  preservation,  , 

The  quantity  of  water  in  well-baked  wheaten  bread  amounts  to  about  45 
per  cent.,  or,  in  other  words,  the  bread  we  eat  is  about  one  half  water. 
Bread  that  has  been  kept  for  a  few  days,  loses  the  characteristic  softness 
which  distinguishes  it  when  fresh-baken,  and  becomes  "crumbly,"  and  ap- 
parently drier.  In  this  condition  it  is  known  as  stale  bread.  The  change, 
however,  is  not  due  to  any  lora  of  water,  but  to  a  change  in  the  internal  ar- 
rangement of  the  molecules  of  the  bread. 

The  solubility  of  bread,  and  its  consequent  ready  digestibility,  is  somewhat 
increased  by  toasting,  the  starch  being  thereby  converted  into  a  modified 
gum  (§  689), 

730.  As  the  process  of  fermenting  bread,  in  order  to  render  it  light  and 
porous,  is  troublesome,  and  somewhat  uncertain,  various  attempts  have  been 
made  to  effect  the  same  object  by  other  agencies.  The  best  of  the  substi- 
Btituted  methods  is  Undoubtedly  that  in  which  bi-carbonate  of  soda  and  hy- 
drochloric (muriatic)  acid  are  employed.  A  small,  but  definite  quantity  of 
carbonate  of  soda  is  first  thoroughly  mixed  with  the  flour,  and  enough  pure 
acid  to  perfectly  neutralize  it  is  then  added  to  the  proper  quantity  of  water. 
The  flour  and  the  acid  water  being  then  thoroughly  incorporated,  the  acid 
acts  upon  the  carbonate  of  soda,  decomposes  it,  expels  its  carbonic  acid,  and 

QUESTIONS. — When  is  bread  said  to  be  slacked  baked?  Can  the  alcohol  evolved  in 
bread-baking  be  collected  ?  What  action  does  the  yeast  exert  on  the  starch  of  the  flour? 
What  is  the  general  effect  of  fermentation  on  the  constituents  of  the  bread  ?  What  effect 
has  common  salt  on  bread  ?  What  percentage  of  water  does  bread  contain  ?  What  i« 
Stale  bread  ?  What  occasions  this  change  ?  What  effect  does  toasting  have  upon  bread  ? 
Is  there  any  way  of  rendering  bread  light  and  porous  without  fermentation  ? 


ALCOHOL    AND    ITS     DERIVATIVES.        443 

unites  with  the  soda  to  form  common  salt.  The  result  is  the  production  of  a 
light,  spongy  dough,  as  in  ordinary  fermentation,  while  the  salt  formed  and 
remaining  in  the  dough,  renders  the  addition  of  this  substance,  in  the  first  in- 
stance, unnecessary.  The  most  serious  objection  to  this  plan  is  the  difficulty 
of  procuring  pure  hydrochloric  acid,  and  of  regulating  the  proportions  of  acid  and 
soda.  Tartaric  acid  may  be  substituted  in  the  place  of  hydrochloric  acid,  and 
the  so-called  yeast  powders  are  generally  prepared  by  mixing  bi-carbonate  of 
soda  and  tartaric  acid  in  proper  proportions.  The  carbonate  of  ammonia  is 
also  not  unfrequently  used  (§  525). 

731.  Sources  of  Alcohol . — Alcohol  is  not  a  principle  existing  in 
nature,  elaborated  and  stored  up  by  the  plants ;  but  is  always  a  product  of 
the  -destructive  decomposition  of  highly -organized  matter.      The  principal 
sources  from  which  crude  alcohol  is  obtained,  are  the  most  valuable  of  our 
cereal  grains,  immense  quantities  of  which  are  annually  used  for  this  purpose, 
and  of  course  to  the  same  extent  the  aggregate  supply  of  food  for  man  is  di- 
minished.    The  waste  of  raw  material  which  accompanies  the  manufacture 
of  alcohol  from  grain  is  also  very  great,  since  the  nitrogenized  elements  of  the 
grain  do  not  enter  into  its  composition,  and  are  accordingly  lost  for  any  useful 
purpose ;  while  the  starchy  and  saccharine  constituents  are  converted  to  the 
extent  of  half  their  weight  into  valueless  carbonic  acid  and  water.     Woody 
fiber,  it  will  be  remembered,  has  identically  the  same  composition  as  starch, 
and,  like  it,  may  be  converted  by  the  action  of  acids  into  grape  sugar,  which  is 
capable  of  furnishing  alcohol.     This  process,  however,  by  reason  of  its  ex- 
pense, is  not  practically  useful;  but  its  consideration  has  much  of  interest, 
since  the  discovery  of  a  cheap  and  ready  method  of  converting  woody-fiber, 
and  bodies  of  like  composition  and  character,  into  glucose,  to  be  used  in  the 
manufacture  of  alcohol,  would  prove  one  of  the  most  valuable  discoveries  in 
the  annals  of  science. 

732.  Products  of  the  Action   of  Acids   upon  Alcohol. 
Ether  , — When  equal  weights  of  strong  alcohol  and  oil  of  vitriol  are 

heated  to  ebullition  in  a  retort,  a  colorless,  highly  volatile  liquid  distils  over, 
which  is  known  as  tilier,  or  sulphuric  ether.  As  soon  as  the  contents  of  the 
retort  blacken  and  froth,  the  process  must  be  discontinued,  or  otherwise  the 
distillate  will  be  contaminated  by  other  substancea 

The  formation  of  this  liquid  may  be  explained  as  follows :  alcohol  is  as- 
sumed to  be  the  hydrated  oxyd  of  an  organic  radical  ethyle,  its  composition 
being  represented  by  the  formula  C4H602=C4H50-f-HO.  When  sulphuric 
acid  is  added  to  alcohol  and  heated,  it  unites  with  the  oxyd  of  ethyle  to  form 
a  bi-sulphide  (C4H50,2S03),  and  from  this  compound  at  a  higher  temperature 
the  oxyd  of  ethyle  (ether)  separates  and  distils  over  as  a  vapor.  The  alcohol, 
therefore,  is  converted  into  ether  by  the  simple  loss  of  an  atom  of  water. 
The  prefix  sulphuric,  as  applied  to  ether,  is  merely  intended  to  indicate  its 

QUESTIONS. — What  are  yeast  powders  ?  What  is  said  of  the  sources  from  which  alcohol 
is  manufactured,  and  of  its  production  ?  How  is  ether  prepared  ?  What  is  the  theory 
of  its  production  ?  Does  sulphuric  ether  contain  any  sulphuric  acid  ? 


444  OKGANIC    CHEMISTRY. 

origin  and  distinguish  it  from  other  bodies  of  like  character,  since  it  contains 
no  sulphuric  acid  in  its  composition. 

Ether  is  a  colorless,  transparent,  fragrant  liquid,  exceedingly  thin  and  mo- 
bile. It  boils  at  96°  F.  (or  when  exposed  to  the  sun  in  summer),  and  may  be 
frozen  by  exposure  to  severe  cold.  In  the  open  ah*  it  evaporates  with  great 
rapidity,  and  occasions  thereby  a  degree  of  cold  sufficient  even  to  freeze  water 
(§  164).  This  property  may  be  illustrated  by  allowing  a  few  drops  of  it  to  evapo- 
rate upon  the  hand.  It  is  highly  combustible,  both  in  the  state  of  liquid  and 
vapor,  and  on  this  account  should  never  be  brought  near  a  flame.  With 
atmospheric  air,  or  oxygen,  its  vapor  forms  explosive  mixtures.  This  may 
be  experimentally  shown  by  pouring  a  few  drops  into  a  tumbler,  and  after 
a  little  time  applying  a  burning  taper.  Ether  mixes  with  alcohol  in  all  pro- 
portions, but  is  very  sparingly  soluble  in  water.  It  dissolves  most  oily  and 
fatty  substances  with  great  readiness,  but  its  solvent  powers  generally  are  far 
more  limited  than  those  of  alcohol. 

When  the  vapor  of  ether,  mixed  with  atmospheric  air,  is  inhaled,  it  pro- 
duces at  first  a  species  of  intoxication,  which  is  speedily  succeeded  by  a  kind 
of  stupor,  during  which  the  system  is  nearly  insensible  to  pain.  This  impor- 
tant property  is  not,  however,  confined  to  ether  alone,  but  is  possessed  by 
nearly  all  the  gaseous  hydrocarbons,  and  by  some  in  a  much  greater  de- 
gree. Ether,  however,  was  the  first  substance  employed  as  an  anesthetic 
agent,  and  under  all  circumstances  must  be  regarded  as  the  safest,  no  acci- 
dents from  its  moderate  inhalation  having  ever  been  recorded. 

733.  Varieties  of  Ether  , — By  distilling  alcohol  with  various  acids, 
different  combinations  of  the  radical  ethyle  may  be  produced,  which  are  gen- 
erally spoken  of  as  kinds  of  ethers.     Thus,  by  distilling  a  mixture  of  alco- 
hol, sulphuric  and  acetic  acids,  we  obtain  an  exceedingly  fragrant,  volatile 
liquid,  acetate  of  the  oxyd  of  ethyle,  or  acetic  ether.     The  fragrant  odor  of 
this  body  may  be  evolved  by  slightly  heating  in  a  test  tube  a  mixture  of 
the  above-named  substances.     In  like  manner,  with  the  aid  of  nitric  acid  we 
may  obtain  a  nitrous  ether,  which  is  much  used  in  medicine  under  the  name 
of  sweet  spirits  of  niter ;  and  with  butyric  acid,  a  butyric  etlwr,  which  has  the 
odor  of  rum,  and  is  now  prepared  for  the  purpose  of  imparting  to  alcohol 
this  flavor  in  the  fabrication  of  liquors. 

734.  Products  of   the   Oxydation  of  Alcohol . — When  al- 
cohol or  ether  are  burned  in  free  air,  the  products  of  combustion,  as  with  all 
similar  hydrocarbons,  are  carbonic  acid  and  water.     Under  certain  circum- 
stances, however,  these  substances  undergo  a  partial  oxydation,  in  which  the 
hydrogen  alone  is  oxydated  or  separated,  leaving  the  carbon  unaffected. 
The  result  is  the  formation  of  a  series  of  compounds  which  are  supposed  to 
contain  a  new  organic  radical  called  acetyle,   C4H3,  derived    from  ethyle, 
C^s,  by  the  removal  of  2  equivalents  of  hydrogen  by  oxydation. 

QUESTIONS.— What  are  the  properties  of  ether  ?  What  is  said  of  its  solvent  powers  f 
What  of  its  anaesthetic  properties  ?  Is  this  property  confined  to  ether  ?  How  may  dif- 
ferent varieties  of  ether  be  prepared  ?  Illustrate  this  hy  examples.  What  is  the  product 
of  the  ordinary  combustion  of  alcohol  ?  What  is  acetyle  ?  How  is  it  formed  ? 


ALCOHOL     AND     ITS     DERIVATIVES.        445 

135.  Aldehyde  • — The  first  known  product  of  this  series  is  a  hydrate 
of  the  oxyd  of  acetyle,  C4lI30-f-HO,  called  aldehyde  (from  al,  alcohol,  de,  from 
which,  hyd,  hydrogen,  is  taken).  It  is  a  limpid,  colorless  liquid,  possessing  a 
peculiarly  suffocating  odor,  and  may  be  prepared  by  distilling  a  mixture  of 
alcohol,  oil  of  vitriol,  and  the  peroxyd  of  manganese.  It  may 
also  be  easily  produced,  and  its  characteristic  odor  illustrated, 
by  plunging  a  coil  of  fine  platinum  wire  heated  to  redness  into  a 
vessel  containing  a  mixture  of  alcohol  or  ether  vapor,  and  at- 
mospheric air.  (See  Fig.  228,  also  §  469.)  The  aldehyde  is 
formed  in  this  experiment  because  the  oxydation  is  not  sufficient 
to  occasion  a  complete  combustion  of  the  alcohol  vapor.  Alde- 
hyde dissolves  sulphur,  phosphorus,  and  iodine,  and  is  especially 
remarkable  for  its  affinity  for  oxygen,  in  consequence  of  which 
it  is  capable  of  reducing  many  of  the  metallic  salts.  The  addi- 
tion of  a  little  aldehyde  in  water  to  an  ammoniacal  solution  of 
nitrate  of  silver,  occasions  the  immediate  precipitation  of  the  silver  as  a  bril- 
liant white  metal. 

736.  Acetic  Acid  is  well  known  as  the  acid  of  vinegar,  which  latter 
substance  is,  in  fact,  a  very  dilute  acetic  acid,  containing  also  much  saccharine 
and  mucilaginous  matter.  Acetic  acid  is  regarded  as  a  hydrated  teroxyd  of 
the  same  radical,  acetyle,  which  enters  into  the  composition  of  aldehyde — ita 
composition  being  represented  by  the  formula  C^tHsOs-j-HO. 

Alcohol,  when  pure,  or  merely  mixed  with  water,  undergoes  no  change 
when  exposed  to  the  air ;  but  the  presence  or  contact  of-  various  foreign  sub- 
stances, dispose  it  to  absorb  oxygen.  Thus,  if  a  few  drops  of  strong  spirits  of 
wine  be  let  fall  upon  a  little  platinum  black,  the  oxygen  condensed  in  the 
pores  of  the  latter  unites  so  rapidly  with  the  alcohol,  as  to  occasion  its  instant 
inflammation.  Under  the  same  circumstances,  when  th£  spirit  is  mixed  with 
a  little  water,  oxydation  still  takes  place,  but  with  less  energy,  and  the  alco- 
hol is  converted  into  acetic  acid.  In  these  transformations  the  platinum 
itself  experiences  no  change.  The  oxydation  of  alcohol,  through  the  agency 
of  platinum  black,  may  be  experimentally  exhibited,  also,  by  placing  a  capsule 
containing  platinum  black  upon  a  plate  by  the  side  of  a  small  vessel  of  alco- 
hol, and  exposing  the  whole,  covered  with  a  bell-glass,  to  the  sunshine. 
In  a  short  time,  the  vapor  of  acetic  acid  will  be  observed  to  condense  on  the 
sides  of  the  jar,  and  run  down  in  drops ;  and  by  occasionally  admitting  fresh 
air,  the  whole  of  the  alcohol  may  in  a  few  hours  be  acidified. 

The  oxydation  of  alcohol,  at  the  expense  of  the  oxygen  of  the  air,  is  also 
effected  by  the  presence  of  almost  any  azotized  matter  (ferment)  susceptible 
of  putrefaction.  Cider,  wine,  and  beer  naturally  contain  such  substances,  and 


QXTEBTIONS.—  What  is  aldehyde  ?  What  are  its  properties  ?  How  is  it  formed  ?  What 
is  the  acid  contained  in  vinegar  ?  What  is  its  chemical  composition  ?  Under  what  cir- 
cumstances is  alcohol  oxydated?  How  may  the  transformation  of  alcohol  into  acetic  acid 
be  illustrated?  "What  is  the  action  of  ferments  on  alcohol?  Why  do  cider,  beer,  etc., 
turn  sour  by  exposure  to  the  air  ? 


446 


ORGANIC     CHEMISTRY. 


therefore  readily  undergo  acetous  fermentation  when  exposed  to  the  air,  at  a 
moderate  temperature,  and  become  converted  into  vinegar  (acetic  acid). 
During  this  fermentation  of  alcoholic  liquors,  a  mucilaginous  substance,  con- 
sisting chiefly  of  albuminous  matter,  is  separated,  which,  from  its  influence  in 
exciting  or  promoting  acetous  fermentation,  is  popularly  termed  the  mother  of 
vinegar.  Acidification  of  this  character  occurs  most  readily  immediately  after 
a  spirituous  fermentation  which  has  taken  place  at  too  high  a  temperature ; 
hence  brewers,  during  the  summer  months,  experience  much  trouble  in  pre- 
venting their  fermenting  wort  and  mash  from  turning  sour. 

737.  Vinegar  is  now  manufactured,  on  a  large  scale,  directly  from  alcohol, 
by  diluting  it  with  water,  adding  a  little  yeast,  and  exposing  the  mixture  to 
the  air.  This  last  is  best  effected  by  causing  the  liquor  to  trickle  slowly 
through  a  cask  filled  with  shavings  of  beech- 
wood,  and  arranged  as  is  represented  in  Fig. 
229.  The  head  of  the  cask,  d,  is  closed  with 
a  shelf,  c,  perforated  with  many  small  holes, 
through  which  threads  are  passed  to  conduct 
the  liquor  downward,  and  distribute  it  evenly 
over  the  interior.  The  shavings,  first  soaked 
in  vinegar,  are  placed  loosely  in  the  cask, 
a  free  circulation  of  air  between  them  being 
provided  for  by  means  of  holes,  a,  in  the 
sides  of  the  cask.  In  this  way  the  alco- 
holic liquor  is  caused  to  present  an  immense 
extended  surface  to  the  action  of  the  air,  and 
oxydation  takes  place  so  rapidly,  that  very 
frequently,  by  the  time  the  liquid  has  trickled 
to  the  bottom  of  the  cask,  it  no  longer  con- 
tains any  alcohol,  but  is  entirely  converted  into  vinegar.  Usually,  however,  it 
is  necessary  to  pass  the  liquid  through  the  apparatus  a  number  of  times  before 
this  change  can  be  completely  effected.  The  presence  of  acetic  acid  itself 
assists  the  action  of  acidification,  and  it  is  for  this  reason  that  the  shavings 
are  soaked  in  vinegar  before  using.  This  process  is  known  as  the  quick 
method  of  making  vinegar. 

The  pyroligneous  acid  (or  wood  vinegar),  obtained  by  the  distillation  of 
hard- wood  in  close  vessels  (§  680),  is  an  impure  acetic  acid,  and  as  such  is 
largely  used  in  dyeing  and  calico-printing;  the  presence,  however,  of  certain 
empyreumatic  substances  extracted  from  the  wood,  impart  to  it  a  disagreeable, 
smoky  odor,  and  render  it  unfit  for  purposes  of  domestic  economy. 

The  acid  liquids  obtained  by  the  above-mentioned  processes,  are  not  pure 
acetic  acid,  but  merely  solutions  of  it  in  water.  This  may  be  concentrated,  but 


QTTESTIONS. — What  is  the  mother  of  vinegar?  Under  what  circumstances  does  acidifi- 
cation occur  most  readily?  Describe  the  quick  process  of  making  vinegar?  What  other 
product  is  a  source  of  acetic  acid  ?  Is  the  acid  liquid  obtained  by  the  oxydation  of  alcohol 
pure  acetic  acid  ? 


ALCOHOL     AND     ITS     DERIVATIVES.        447 

if  we  attempt  to  obtain  the  acid  free  from  any  water  by  distillation,  it  is  dc- 
c  jmposed.  Acetic  acid  in  a  separate  state  is  prepared  by  neutralizing  vinegar 
with  soda  or  lime,  evaporating  to  dryness,  and  distilling  the  solid  residue  in 
connection  with  sulphuric  acid.  The  evolved  vapors  condensed,  furnish  a 
colorless,  intensely-sour  liquid,  which  possesses  a  pungent,  fragrant  odor,  and 
blisters  the  skin.  It  mixes  with  water  in  all  proportions,  forming  vinegars  of 
different  degrees  of  strength,  Common  table'  vinegar  usually  contains  from 
3  to  6  per  cent,  of  acetic  acid.  The  salts  of  vinegar,  sold  by  druggists  as  a 
reviving  scent  in  sickness  and  fainting,  consist  of  sulphate  of  potash,  impreg- 
nated with  acetic  acid.  Acetic  acid  dissolves  many  organic  bodies,  such  as 
gluten,  gelatine,  gum,  resins,  the  white  of  eggs,  etc.;  hence,  its  use  as  vine- 
gar, in  moderation,  promotes  digestion.  When  vinegar  i-;  exposed  to  cold,  the 
water  contained  in  it  is  frozen  before  the  acetic  acid  is ;  hence,  weak  vinegar 
is  made  stronger  by  partial  freezing. 

738.  Salts   of  Acetic    Acid . — Acetic  acid  unites  with  most  bases  to 
form  an  important  class  of  salts  called  acetates,  all  of  which  are  soluble  in 
water.     Acetate  of  lead,  PbO,  C^I-jOg,  the  sugar  of  lead  of  commerce,  is  a  white 
salt  formed  by  dissolving  oxyd  of  lead  (litharge)  in  acetic  acid.     It  possesses 
a  very  sweet  astringent  taste,  and  is  often  employed  in  medicine,  but  when 
taken  internally  in  any  other  than  minute  quantities  is  n  poison.     Acetate  of 
copper  constitutes  verdigris  (§  G13).     Acetates  of  alumina  and  of  iron  are 
salts  much  used  in  dyeing  and  calico  printing. 

739.  M  e  t  h  y  1  i  c    Alcohol , — In  connection  with  the  pyroligneous  aoid 
obtained  by  the  distillation  of  wood  in  close  vessels,  there  also  passes  over  a 
Volatile  inflammable  liquid,  which  is  allied  to  alcohol  in  its  composition  and 
properties.     This  substance  in  its  pure  state  is  known  as  methylic  alcohol,  or 
wood-spirit,  and  is  supposed  to  be  the  hydrated  oxyd  of  a  radical  called 
methyle,  the  constitution  of  which  is  represented  by  the  formula  CaHg,  and 
that  of  its  alcohol  by  CsIIsO-pHO.     Crude  pyroligneous  acid  contains  about 
1-1 00th  of  its  weight  of  this  substance,  which  is  separated  from  it  by  distil- 
lation.    It  occurs  as  an  article  of  commerce,  and  is  often  substituted  for  al- 
cohol in  various  processes  in  the  arts.     Its  odor,  however,  is  quite  different 
from  that  of  ordinary  alcohol. 

740.  Formic    Acid  , — As  alcohol  by  oxydation,  under  the  influence 
of  finely  divided  platinum,  gives  rise  to  acetic  acid,  so  wood-spirit,  under 
similar  circumstances,  produces  an  acid  product  which  has  been  called  formic, 
from  the  circumstance,  that  a  similar  acid  may  bo  extracted  from  ants  by 

'  distilling  them  with  water.  As  acetic  acid  is  regarded  as  the  hydrated  ter- 
oxyd  of  the  radical  acetyle,  so  formic  acid  is  considered  as  the  hydrated  ter- 
oxyd  of  a  new  radical  formyk,  which  is  derived  from  methyle  as  acetyle  is 
from  ethyle — the  formula  of  formyle  being  Call,  and  that  of  formic  acid, 

QUESTIONS. — How  is  acetic  acid  prepared  ?  "What  are  the  properties  of  acetic  acid  ? 
What  are  salts  of  vinegar  ?  What  is  said  of  vinegar  ?  What  are  acetates  ?  What  is  sugar 
of  lead  ?  What  are  other  important  acetates  ?  What  is  said  of  methylic  alcohol  ?  What 
is  its  chemical  constitution  ?  What  is  formic  acid  ?  What  is  its  composition  ? 


448  ORGANIC     CHEMISTRY. 

CoH,03-rHO.    Formic  acid  also  unites  with  bases  to  form  salts,  which  closely 
resembles  the  acetates. 

741.  Chloroform,    C2H  C  1  .-—This  substance,  which  is  regarded  as  a 
terchloride  of  the  radical  formyle,  is  best  obtained  by  distilling  alcohol,  or 
wood-spirit,  with  a  solution  of  chloride  of  lime  (bleaching  powder).     It  is  an 
oily,  colorless  liquid,  of  an  agreeable,  ethereal  odor,  and  of  a  sweetish  taste. 
An  alcoholic  solution  of  chloroform,  prepared  by  distilling  chloride  of  lime 
with  an  excess  of  alcohol,  is  known  in  medicine  by  the  incorrect  name  of 
chloric  ether )  and  is  the  liquid  which  is  now  generally  sold  and  used  under 
the  name  of  chloroform.     The  vapor  of  chloroform,  when  inhaled  with  atmos- 
pheric air,  produces  anaesthetic  effects,  like  the  vapor  of  ether.     It  is,  how- 
ever, much  more  potent  and  agreeable  than  ether,  and  has  to  a  considerable 
extent  replaced  the  latter  agent  in  surgical  practice.     Chloroform,  unless  pre- 
pared from  perfectly  pure  alcohol,  is  liable  to  contain  certain  foreign  and 
volatile  compounds,  which  exert  a  most  deleterious  and  often  fatal  effect  upon 
the  system  when  inhaled.     No  person,  therefore,  should  sell  or  use  chloroform 
which  is  not  known  to  have  been  properly  prepared.     Chloroform  is  with 
difficulty  kindled,  and  burns  with  a  greenish  flame.* 

742.  Amylic  Alcohol , — In  the  process  of  distilling  whiskey  from  pota- 
toes, there  is  generated,  in  connection  with  the  crude  spirit,  a  volatile,  oily  body, 
possessing  a  pungent,  disagreeable  odor.     This  substance,  the  complete  sep- 
aration of  which  from  the  crude  spirit  is  a  matter  of  difficulty,  appears  to  be 
analogous,  in  its  composition  and  chemical  reactions,  to  alcohol,  and  is  re- 
garded as  the  hydrated  oxyd  of  a  radical,  termed  amyk, — the  hydrated  oxyd 
itself  being  called  amylic  alcohol,  or  more  generally,  fusel  oil  (from  the  Ger- 
man fuseloct),  or  oil  of  potato  spirits.*    Amylic  alcohol,  in  a  pure  state,  has  the 
appearance  of  a  thin,  colorless  oil ;  it  is  highly  volatile ;  and  the  inhalation  of 
its  vapor,  in  even  a  minute  quantity,  is  attended  with  very  deleterious  effects ; 
the  fatal  accidents  which  have  sometimes  resulted  from  the  use  of  chloroform 
being  generally  ascribed  to  its  admixture  with  this  compound.     It  exists  in 
almost  all  ordinary  alcohol  in  small  quantity,  and  is  the  occasion  of  the  per- 
sistent and  somewhat  faintly-disagreeable  odor  which  alcohol  leaves  upon  a 
surface  after  evaporation. 

The  extraordinary  character  of  the  compounds  and  derivatives  of  amylic 
alcohol  (fusel  oil),  render  it  one  of  the  most  interesting  products  of  organic 


*  A  most  efficient  and  economical  apparatus  for  disinfecting  apartments  and  purifying 
the  air,  may  be  arranged  by  burning  chloric  ether  in  a  simple  camphene  lamp  provided 
•with  one  wick.     In  dissecting-rooms,  in  cellars  where  vegetables  have  decayed,  or  where 
drains  allow  the  escape  of  offensive  gases,  and  in  outbuildings,  no  more  effective  and 
agreeable  method  of  purifying  the  air  can  be  resorted  to. 

*  Amyle  derives  its  etymology  from  the  Latin  amylum,  starch,  the  substance  being  a 
product  of  the  fermentation  of  starch. 

QUESTIONS.— What  is  chloroform?  HO-W  is  It  prepared?  What  are  Its  properties? 
What  is  the  so-called  chloric  ether?  When  is  chloroform  liable  to  be  injurious  ?  What 
is  amylic  alcohol  ?  What  other  name  is  applied  to  it  ?  What  are  its  properties  ?  What 
is  a  characteristic  feature  of  this  substance  ? 


ALCOHOL     AND     ITS     DERIVATIVES.         449 

chemistry — most  of  the  substances  into  which  its  constituents  enter  as  compon- 
ents being  characterized  by  very  singular  and  remarkable  odors.  For  example, 
when  amylic  alcohol  is  warmed,  and  dropped  upon  platinum  black,  it  oxydizes 
and  forms  an  acid,  which  bears  the  same  relation  to  its  alcohol  that  acetic 
acid  does  to  ordinary  alcohol.  This  compound  possesses  in  an  intense  degree 
the  odor  of  valerian,  and  is  believed,  furthermore,  to  be  identical  with  the 
acid  which  imparts  to  the  root  of  the  plant  valerian  its  odor  and  medicinal 
properties:  it  has  hence  been  called  valerianic  acid,  and  has  been  advantage- 
ously employed  in  medicine  in  place  of  the  natural  extract. 

By  distilling  amylic  alcohol,  under  proper  circumstances,  with  various 
acids,  we  obtain  odoriferous  compounds,  which,  during  the  last  few  years, 
have  become  familiarly  known  as  "fruit  extracts,"  or  "essences,"  and  as 
"liquor  flavoring  materials."  Thus  amylic  alcohol,  distilled  with  sulphuric 
acid  and  acetic  acid  (acetate  of  potash),  yields  an  oily  product  which  possesses 
most  perfectly  the  odor  of  the  "  Jargonelle"  pear ;  chromic  acid,  substituted  in 
the  place  of  acetic  acid,  gives  oil  of  apples ;  while  other  acids  yield  products 
possessing  the  flavors  of  the  banana,  the  orange,  and  many  other  fruits.  In 
the  same  manner,  the  flavoring  principles  which  characterize  spirituous  liquors 
may  be  obtained,  and  indeed  are  now  manufactured  and  sold  extensively 
under  the  names  of  "oil  of  cognac,"  "  oil  of  wine,'1  etc.,  for  the  fabrication  of 
almost  any  kind  of  liquor  or  wine,  from  pure  alcohol.*  Although  prepared 
from  a  poisonous  basis  (fusel  oil),  these  extracts  do  not  appear  to  possess  any 
injurious  qualities,  when  used  in  moderate  quantities  as  flavoring  agents;  and 
the  position  has  even  been  taken  by  some  chemists  that  they  are  identical  in 
composition  with  the  perfumes  which  nature  carefully  elaborates  in  different 
fruits  and  plants.  In  addition  to  perfumes  the  most  agreeable,  however, 
odors  of  the  most  disgusting  and  nauseous  character  can  also  be  produced 
by  like  means,  as,  for  instance,  the  odor  of  the  bed-bug,  squash-bug,  and  of 
many  disagreeable  plants  and  weeds.  The  basic  radical  employed  for  this 
purpose  is  not,  however,  in  all  instances  amyle,  as  the  same  properties  are 
characteristic  to  some  extent  of  a  number  of  analogous  radicals. 

743.  Sulphur  Alcohols,  or  Me.  reap  tans  , — By  various  indi- 
rect processes,  the  oxygen  of  wine,  methylic  and  amylic  alcohol,  may  be  re- 
placed by  sulphur,  their  other  constituents  remaining  unaltered,  and  in  this 
way  a  series  of  bodies  may  be  produced,  which  from  their  resemblance  in 


*  A  few  drops  of  oil  of  cognac,  added  to  a  glass  of  water  colored  with  burnt  sugar  (car- 
amel), will  convert  it,  so  far  as  appearance  and  odor  is  concerned,  into  a  fair  article  of 
dark  brandy.  Manufacturers,  in  fabricating  spirituous  liquors  from  alcohol,  by  the 
aid  of  these  flavoring  extracts,  find  it  necessary  to  use  an  article  of  spirits  from  which 
every  trace  of  fusel  oil  has  been  previously  extracted,  as  this  substance,  in  a  separate 
state,  seems  to  destroy  flavoring  extracts  which  contain  its  elements  as  constituents.  This 
separation  of  fusel  oil  from  alcohol  is  now  accomplished  by  distilling  the  crude  spirit  in 
connection  with  permanganate  of  potash. 

QUESTIONS— What  is  valerianic  acid  ?  What  are  other  derivatives  of  this  body  ?  What 
we  the  so-called  Bulphur  alcohols,  or  mercaptans  ? 


450  ORGANIC    CHEMISTRY. 

composition  to  alcohol,  have  been  called  sulphur  alcohols,  or  by  reason  of 
their  great  affinity  for  mercury,  mercaptans  (mercurium  captans).  Thus  the 
composition  of  wine  alcohol  being  C4H602,  its  mercaptan  would  be  C4H6S2. 
These  products  in  their  properties  closely  resemble  the  oily  compounds  which 
impart  to  garlic,  the  onion,  and  other  plants  of  like  character  their  offensive 
odors,  and  in  fact  may  be  considered  as  artificial  oils  of  garlic.  The  mer- 
captan produced  from  methylic  alcohol  is  a  colorless  liquid,  with  a  most  of- 
fensive and  concentrated  odor  of  onions,  which  penetrates  and  obstinately 
adheres  to  every  substance  with  which  it  is  brought  in  contact. 

744.  If  we  replace  the  sulphur  existing  in  these  fetid  compounds  with  ar- 
senic, we  produce  new  volatile  substances  which  are  not  only  insufferable  in 
their  smell,  but  rank  among  the  most  deadly  poisons  known  to  chemists. 

Such  a  compound  is  kakodyle  (from  /oa/cof,  evil,  and  vTiij,  principle),  formed 
by  the  union  of  arsenic  with  the  radical  methyle,  and  which,  from  the  cir- 
cumstance that  it  fulfils  in  composition  the  part  of  an  element  in  a  very  re- 
markable manner,  has  been  studied  by  chemists  with  great  minuteness.* 
United  with  cyanogen,  it  forms  cyanide  of  kakodyle,  a  compound  possessed 
of  most  deadly  qualities.  "  "When  exposed  to  the  air  it  rises  in  the  form  of 
vapor,  which  by  contact  with  moisture  is  instantly  decomposed,  its  arsenic 
uniting  with  oxygen  to  form  fumes  of  arsenious  acid,  while  the  cyanogen  by 
combination  with  hydrogen  forms  prussic  acid;  and  thus  at  the  same  in- 
stant the  air  is  impregnated  with  vapors  of  the  two  most  deadly  poisons 
with  which  we  are  acquainted."  The  evaporation  of  a  few  grams  of  cyanide 
of  kakodyle  in  the  atmosphere  of  a  room,  is  said  to  produce  almost  instan- 
taneous unconsciousness.  In  addition  to  these  substances,  many  other  com- 
pounds of  a  somewhat  similar  character  have  been  formed  and  described, 
and  it  has  sometimes  been  proposed  to  employ  them  as  ingredients  in  ex- 
plosive war  projectiles  (asphyxiating  bombs). 


CHAPTER    XX. 

VEGETABLE     ACIDS. 

745.  OVER  two  hundred  distinct  acid  compounds,  the  products  of  the 
vegetable  kingdom,  have  been  isolated  and  described  by  chemists.  They  are 
all  composed  of  carbon,  hydrogen,  and  oxygen,  with  the  latter  element  gen- 
erally in  large  excess.  They  are  not,  however,  usually  found  in  plants  in  a 


*  A  recent  chemical  authority  has  described  the  odor  of  this  compound  as  far  exceeding 
in  offensiveness  the  fetor  exhaled  by  any  animal  or  vegetable. 

QUESTIONS. — What  are  their  properties  ?  By  replacing  sulphur  with  arsenic,  what  com- 
pounds are  formed  ?  What  is  kakodyle  ?  What  are  its  properties  ?  What  is  said  of  the 
number  and  distribution  of  the  vegetable  acids? 


VEGETABLE    ACIDS. 


451 


free  state,  but  in  combination  with  various  bases  derived  from  the  soil,  such 
FIG.  230.  as  potash,  soda,  lime,  etc.     The  salts      FIG.  231. 

thus  formed  are  sometimes  neutral,  but 
more  frequently  acid  in  their  charac- 
ter,  and  consequently  impart  to  the 
portions  of  the  plant  containing  them 
a  distinctly  acid  taste  and  reaction. 
..,  ..  "When  the  salt  is  sparingly  soluble,  it 

//  /I  /1V  u  °ften  accumulates  in  the  cells  of  the 
LJ  It  <Tr7  \  plant  hi  the  form  of  minute  crystals, 
which  are  readily  discernible  by  the 
microscope.  Fig.  230  represents  crys- 
tals of  this  character  found  in  the  onion,  and  Fig.  231  crystals 
of  oxalate  of  potash  occurring  in  the  rhubarb. 

Some  of  these  acids  are  very  widely  diffused  in  the  vegetable 
kingdom,  but  the  majority  occur  in  only  a  few  particular  plants, 
and  in  minute  quantities.     The  most  important  of  them  only  require  special 
consideration. 

746.  Oxalic  Acid,  C2  03  H  0  , — This  acid  is  found  abundantly  in  many 
plants  in  combination  with  potash  and  lime,  and  is  the  principle  of  acidity  in 
the  leaves  of  the  sorrel  and  the  rhubarb  (pie-planf).  It  is  also  a  constituent  in 
certain  minerals.  For  practical  purposes  it  is  prepared  artificially  by  digest- 
ing sugar  with  strong  nitric  acid;  thus,  when  these  two  substances  are  gently 
heated  in  connection,  in  the  proportion  of  1  part  of  sugar  to  8  of  acid,  violent 
action  ensues,  accompanied  with  a  disengagement  of  copious  fumes  of  nitrous 
acid ;  and  the  solution  remaining  after  the  cessation  of  the  action,  furnishes, 
by  evaporation,  crystallized  oxalic  acid.  Starch,  woody  fiber,  and  many  other 
organic  substances,  treated  in  the  same  manner,  yield  the  same  product. 

In  its  pure  state,  oxalic  acid  is  a  crystalline  solid,  not  unlike  Epsom  salts,  for 
which  it  is  not  unfrequently  mistaken.  It  possesses,  however,  an  intensely 
sour  taste  (which  Epsom  salts  does  not),  is  freely  soluble  in  water,  and  when 
taken  internally,  is  highly  poisonous,  occasioning  death  in  a  few  hours.  The 
proper  antidote  for  it  is  the  administration  of  chalk  or  magnesia,  suspended  in 
water. 

Oxalic  acid  is  extensively  employed  in  calico-printing,  and  to  some  extent 
by  straw  and  Leghorn  bonnet-makers,  for  the  purpose  of  cleansing  their 
wares.  It  is  also  used  in  chemical  analysis  as  an  exceedingly  delicate  test 
for  the  presence. of  lime,  or  any  of  its  soluble  compounds.  The  salts  formed 
by  oxalic  acid  are  termed  oxalates.  Binoxalate  of  potash,  which  is  often  ex- 
tracted from  certain  species  of  sorrel,  is  sold  under  the  name  of  "salts  of  sor- 
rel," or  "essential  salts  of  lemons,"  for  the  purpose  of  discharging  iron-rust,  or 
ink-stains  from  linen.  Its  use  for  this  purpose  depends  upon  the  fact,  that 

QUESTIONS — What  is  said  of  the  occurrence  of  oxalic  acid  ?  How  is  it  obtained  for  in- 
dustrial purposes  ?  What  are  its  properties  ?  What  its  uses  ?  What  are  its  salts  called  ? 
What  are  salts  of  sorrel  or  of  lemons  ?  How  are  they  operative  in  removing  ink-stains  ? 


452  ORGANIC    CHEMISTRY. 

oxyd  of  iron  (the  basic  coloring  matter  of  ink)  is  readily  soluble  in  oxalic  acid, 
and  therefore  leaves  the  fiber  and  forms  an  oxalate  of  iron.  The  corrosive 
powers  of  the  acid  are  not  sufficient  to  injure  the  fibers  of  the  linen,  if  it  be 
speedily  removed  by  washing. 

747.  Tartaric   Acid,   CsH4  Oi0,  2  H  0 ,  in  combination  with  potash, 
exists  in  many  fruits,  and  is  especially  the  acid  principle  of  grapes.     When 
the  expressed  juice  of  the  grape  is  fermented,  as  in  the  manufacture  of  wine, 
the  tartaric  acid,  in  combination  with  potash,  forming  an  impure  tartrate  of 
potash,  gradually  separates  from  the  liquor,  and  deposites  itself  as  a  crust 
upon  the  interior  of  the  casks,  and  in  this  condition  is  known  in  commerce  as 
argals,  or  crude  tartar.     The  pure  acid  obtained  from  this  source  is  a  white, 
crystallized  solid,  freely  soluble  in  water,  and  of  an  agreeable,  acid  taste. 

Tartaric  acid  forms  with  potash  two  salts, — the  neutral  tartrate,  containing 
2  atoms  of  alkali  to  1  of  acid,  2KO,  C8H4Oi0 ;  and  the  acid,  or  bi-tartrate,  in 
which  an  atom  of  potash  is  replaced  by  an  atom  of  water,  thus,  KO,  HO,  Cs 
HiOio.  This  latter  salt  is  the  well-known  "  cream  of  tartar."  By  saturating 
a  solution  of  cream  of  tartar  with  soda,  a  double  tartrate  of  potash  and  soda 
is  formed,  which  is  extensively  used  in  medicine  as  a  mild  purgative,  under 
the  name  of  "  Rochelle  salts,"  or  "  powders."  Tartaric  acid,  mechanically 
mixed  with  bi-carbonate  of  soda,  constitutes  the  so-called  "  soda  powders,"  or 
the  ingredients  of  the  ordinary  effervescing  draughts.  Tartaric  acid  is  chiefly 
employed  in  dyeing. 

748.  Citric   Acid  is  the  principal  acid  which  imparts  sourness  to  the 
lemon,  orange,  and  the  cranberry ;  but  also  exists  in  many  other  fruits,  as  the 
currant,  gooseberry,  etc.     It  is  readily  obtained  from  the  juice  of  the  lime  and 
lemon  (citron),  and  is  used  in  calico-printing,  in  medicine,  and  in  domestic 
economy,  as  a  flavoring  material.     Citric  acid,  by  heating,  passes  into  aconitic 
acid,  an  acid  which  occurs  native  in  the  plant  called  "monk's  hood." 

749.  Malic  Acid  was  first  obtained  from  the  juice  of  the  apple  (hence 
its  name  from  the  Latin  malum,  an  apple).     It  is  the  most  widely  diffused  of 
all  the  vegetable  acids,  and  is  the  cause  of  acidity  in  most  unripe  fruits.    For 
practical  purposes  it  is  usually  obtained  from  the  berries  of  the  mountain-ash, 
though  it  exists  abundantly  in  the  stalks  of  the  rhubarb,  in  the  pear,  the 
cherry,  the  raspberry,  the  strawberry,  and  many  similar  fruits. 

760.  Tannic  Acid,  or  Tannin,  is  the  general  name  given  to  various 
substances  (probably  of  somewhat  different  composition),  which  are  exten- 
sively diffused  in  plants,  and  which  are  characterised  by  a  well-known  puck- 
ering and  astringent  taste.  They  are  regarded  as  acids,  since  they  possess  an 
acid  taste,  and  are  capable  of  uniting  with  bases  to  form  salts.  Tannic  acid 
exists  in  almost  all  vegetables,  in  the  bark  and  leaves  of  trees,  and  in  the 
seeds  of  fruits.  It  is,  however,  most  abundant  in  the  bark  of  the  oak  and  the 

QUESTIONS.—  What  is  said  of  tartaric  acid  ?  What  are  argals  ?  What  is  cream  of  tar- 
tar? What  are  Rochelle  powders  ?  What  are  soda  powders  ?  What  is  said  of  citric  acid  ? 
What  of  malic  acid  ?  What  is  tannin  or  tannic  acid  ?  In  what  substances  is  tannin  most 
abundant  ? 


VEGETABLE     ACIDS.  453 

hemlock,  in  the  fruit  and  stems  of  the  sumach,  and  especially  in  nut-galls, 
which  are  excrescences  produced  upon  the  branches  and  leaves  of  certain  spe- 
cies of  oak,  by  the  puncture  of  insects.  Green  and  black  teas  contain  from  8 
to  10  per  cent,  of  tannin,  which  imparts  to  them  their  strong,  astringent  qual- 
ities. Tannic  acid  is  freely  soluble  in  water,  and  is  readily  obtained  in  solu- 
tion, by  digesting  the  portions  of  the  plant  containing  it  in  water. 

751.  Leather . — The  most  remarkable  feature  of  tannic  acid,  is  its  prop- 
erty of  uniting  and  forming  insoluble  compounds  with  albumen,  gluten,  gela- 
tin, and  with  the  skin  and  tissues  of  animals  in  general.     Such  compounds 
will  not  putrefy,  and  are  unchangeable  in  water.     This  principle  is  practically 
applied  in  the  manufacture  of  leather,  which  is  effected  by  steeping  the  skins 
of  animals,  which  consist  chiefly  of  gelatin,  in  aqueous  infusions  of  barks 
containing  a  large  percentage  of  tannic  acid.*     Some  varieties  of  skins  may 
be  tanned  in  a  few  days,  or  even  hours ;  but  for  the  production  of  the  best 
qualities  of  leather,  they  are  allowed  to  remain  in  contact  with  the  tan  liquor 
from  9  to  15  months,  and  often  for  a  period  of  years. 

752.  Inks . — When  a  solution  of  tannin  is  brought  in  contact  with  salts 
of  the  sesquioxyd  of  iron,  it  yields  a  deep  bluish-black  precipitate — the  per- 
tannate  of  iron — which  is  extensively  employed  for  dyeing  fabrics  of  a  black 
or  brown  color,  and  in  the  manufacture  of  inks.     Common  writing-ink  is 
formed  by  adding  to  a  clear  infusion  of  nut-galls  a  solution  of  protosulphate  of 
iron  (copperas).     To  prevent  the  precipitate  from  settling,  and  for  thickening 
the  fluid,  a  mucilage  of  gum-arabic  is  also  added.     Ink  thus  prepared  consists 
at  first  principally  of  the  tannate  of  the  protoxyd  of  iron,  and  is  too  pale  for 
use ;  by  exposure  to  the  air,  however,  it  gradually  absorbs  oxygen,  and  is 
converted  into  the  tannate  of  the  sesquioxyd — the  liquid,  at  the  same  time, 
deepening  in  color,  and  finally  becoming  black.     Mouldiness  in  ink  may  be 
prevented  by  the  addition  of  a  small  quantity  of  the  oil  of  cloves,  creosote,  or 
corrosive  sublimate :  the  latter,  in  small  amount,  is  probably  more  efficient 
than  all  the  others ;  but  it  should  be  remembered  that  it  is  a  deadly  poison. 
Faded  writings  can  be  restored  in  a  measure  by  washing  them  with  an  infu- 
sion of  galls,  f 

*  Oak  bark  contains  from  5  to  6  per  cent,  of  tannin ;  and.  in  this,  as  well  as  in  all  other 
astringent  barks,  the  tannin  is  contained  solely  in  the  inner,  white  layers,  next  to  the  sap- 
wood,  or  alburnum.  From  4  to  6  pounds  of  oak-bark  are  required  for  the  production  of  1 
pound  of  leather.  Leather  tanned  with  oak-bark  is  considered  superior  to  that  made  from 
any  other  tanning  material,  but  the  process  is  slower.  Nut-galls  contain  more  tannic  acid 
than  any  other  substance,  the  quantity  varying  from  30  to  40  per  cent.  Sumach  is  used  in 
the  manufacture  of  the  lighter  and  finer  kinds  of  leather.  Sicilian  sumach  contains  about 
16  per  cent,  of  tannin,  and  that  grown  in  the  United  States  from  5  to  10  per  cent. 

t  The  cause  of  the  browning  and  fading  of  ordinary  inks,  results  cliiefly  from  a  per- 
oxygenation  of  the  iron,  and  its  separation  from  the  acid  combined  with  it.  No  salt  of 
iron,  and  no  preparation  of  iron,  equals  the  common  sulphate  (that  is,  commercial  cop- 
peras) for  ink-making,  and  the  addition  of  any  persalt,  such  as  the  nitrate  or  chloride  of 

QUESTIONS.— What  is  its  most  remarkable  property  ?  How  is  leather  prepared  ?  What 
is  the  reaction  of  tannin  with  sesquioxyd  of  iron  ?'  How  is  ink  prepared  t  Why  does  ink 
grow  dark  by  exposure  to  the%ir  ? 


454  ORGANIC    CHEMISTRY. 

The  permanent  black  color  of  the  grain  side  of  the  leather  used  in  the 
manufacture  of  boots  and  shoes  is  also  a  tannate  of  iron,  produced  by  wash- 
ing the  leather  when  in  a  moist  state  with  a  solution  of  the  acetate  of  the 
sesqui-oxyd  of  iron. 

753.  Gallic  Acid  , — This  acid  is  found  naturally  associated  with  tan- 
nin in  vegetable  tissues,  and  is  also  formed  from  tannic  acid  by  exposing 
a  solution  of  the  latter  for  some  time  to  the  action  of  the  air.  It  produces, 
like  tannin,  a  dark  precipitate  with  the  salts  of  the  sesqui-oxyd  of  iron,  but 
does  not  unite  with  gelatin  to  form  insoluble  compounds,  and  is  consequently 
of  no  value  for  the  manufacture  of  leather.  When  added  to  the  salts  of 
silver,  gold,  and  platinum  in  solution,  it  occasions  a  precipitation  of  the  metal 
in  a  state  of  minute  subdivision.  The  most  successful  compounds  for  color- 
ing the  hair  are  founded  upon  this  principle — the  hair  being  wet  in  the  first 
instance  with  a  solution  of  gallic  acid,  and  afterward  with  a  solution  of  a 
salt  of  silver  in  ammonia.  The  reduced  metal  imparts  to  the  hair  a  fine 
black  or  brown  color,  which  is  extremely  permanent. 

In  addition  to  the  substances  mentioned  which  afford  tannin,  there  are 
several  others  which  afford  it  and  constitute  important  articles  of  commerce. 
Among  them  may  be  mentioned  the  following :  catechu,  cutch,  and  terra-japon- 
ica  are  the  dried  aqueous  extracts  of  a  species  of  acacia  growing  in  India ;  kino 
is  a  product  of  like  character ;  divi-divi  is  the  pod  of  a  leguminous  shrub, 
a  native  of  South  America.  These  substances  will  be  found  mentioned  in 
almost  every  commercial  price  current.  The  best  gall  nuts  are  exported  from 
Asia  Minor. 

In  addition  to  the  acids  which  are  secreted  by  living  vegetable  tissues,  a 
great  number  have  been  also  recognized  by  chemists  which  do  not  exist  natu- 
rally in  plants,  but  are  the  result  of  vegetable  decompositions  taking  place 
either  under  natural  or  artificial  conditions.  The  acids  included  in  the  sub- 
stance called  humus,  and  many  of  the  products  resulting  from  the  action  of 
mineral  acids  upon  the  constituents  of  coal-tar,  are  examples  of  this  nature. 

iron,  or  of  logwood,  impairs  the  durability  of  the  ink.  Experiments  recently  detailed  to  the 
Scottish  Society  of  Arts,  show  that  the  quality  and  durability  of  ink  is  greatly  increased, 
however,  by  the  addition  to  it  of  a  small  quantity  of  sulphate  of  indigo,  and  the  following 
receipt  was  given  as  affording  an  ink  that  was  superior  to  all  others  for  writing  pur- 
poses :  12  ounces  powdered  nut  galls,  8  ounces  sulphate  of  indigo,  8  ounces  of  copperas,  a 
few  cloves,  and  4  to  6  ounces  of  gum  arabic  per  gallon  of  ink.  Documents  written  with 
steel  pens  are  less  durable  than  those  written  with  quill  pens,  as  the  contact  of  iron  or 
steel  with  ink,  injures  it  to  a  greater  or  less  extent. 

QUESTIONS. — How  is  a  black  color  given  to  leather  ?  What  is  said  of  gallic  acid  ? 
What  are  its  characteristic  features  ?  What  products  are  commercially  important  on  ac- 
count of  their  twain  ?  What  other  acid  compounds  are  considered  in  this  connection  ? 


ORGANIC     ALKALIES.  455 

CHAPTER    XXI. 

ORGANIC     ALKALIES. 

754  THE  terms  organic  alkalies,  vegetable  alkaloids,  and  organic  bases,  are 
applied  to  a  peculiar  class  of  organic  substances  which  resemble  in  certain 
of  their  properties  the  alkalies  of  inorganic  chemistry ;  that  is  to  say,  they 
neutralize  acids,  unite  with  bases  to  form  salts,  and  in  most  instances,  when 
in  solution,  restore  the  blue  color  of  reddened  litmus. '  They  all  contain  nitro- 
gen as  an  essential  constituent,  and  are  exceedingly  complex  in  their  consti- 
tution. They  are  sparingly  soluble  in  water,  but  dissolve  freely  in  hot  alco- 
hol, from  which  they  often  crystallize  on  cooling  in  a  very  beautiful  manner. 
The  taste  of  these  substances  in  solution  is  usually  intensely  bitter,  and  the 
majority  of  them  are  active  and  virulent  poisons;  when  given,  however, 
in  small  doses,  they  rank  among  the  most  powerful  medicines. 

Of  the  organic  alkaloids,  about  one  hundred  are  now  known  to  exist  in 
plants  as  natural  products,  always  in  combination  with  vegetable  acids.  They 
were  formerly  supposed  to  be  exclusively  the  result  of  vegetable  organiza- 
tion, but  within  a  comparatively  few  years  some  seventy  or  eighty  compounds 
of  a  similar  character  have  been  artificially  prepared  from  organic  products  by 
chemists.  These  last  are  termed  the  artificial  organic  alkaloids,  and  do  not 
occur  in  nature.  The  true  vegetable  bases  have  not  yet  been  artificially  imi- 
tated. 

Most  of  the  vegetable  alkaloids  are  prepared  by  boiling  the  vegetable  mat- 
ter containing  them  in  water  acidulated  with  hydrochloric  acid,  when  the 
alkaloid  unites  with  the  acid  to  form  a  soluble  salt,  and  enters  into  solution. 
From  this  it  is  precipitated  in  a  separate  state  by  the  addition  to  the  liquid 
of  a  stronger  base — i.  e.,  lime,  potash,  ammonia,  etc.  The  plants  which  by 
treatment  furnish  alkaloids,  are  generally  characterized  by  possessing  poison- 
ous or  active  medicinal  qualities,  which  in  turn  are  supposed  to  be  due  to 
the  alkaloids  contained  in  them.  The  following  are  some  of  the  most  impor- 
tant of  the  alkaloids  extracted  from  vegetable  products. 

755.  Morphia  . — Morphine. — This  alkaloid  is  the  chief  active  principle 
of  opium,  which  is  the  dried  juice  of  certain  species  of  the  poppy.  It  exists 
in  opium  in  combination  with  meconic  acid,  and  the  best  qualities  of  opium 
contain  about  ten  per  cent,  of  it.  It  crystallizes  in  small,  colorless  prisms,  ia 
devoid  of  smell,  and  possesses  a  bitter,  unpleasant  taste.  It  is  powerfully  nar- 
cotic and  poisonous,  and  is  an  invaluable  remedy  in  medicine,  in  small  doses, 
for  soothing  nervous  irritation  and  allaying  pain.  A  full  dose  of  pure  morphia 


QOTISTIONS. — What  are  the  organic  alkalies  ?  By  -what  other  names  are  they  desig- 
nated ?  What  are  the  general  properties  of  these  substances  ?  What  is  their  number  ? 
Are  any  of  them  prepared  artificially  ?  How  are  the  vegetable  alkaloids  obtained  ?  What 
are  characteristics  of  the  plants  which  furnish  them?  What  is  morphia?  What  is 
opium  ?  What  are  the  properties  of  morphia  ? 


456  ORGANIC     CHEMISTRY. 

for  a  grown  man  is  one  eighth  of  a  grain ;  and  in  the  state  of  acetate  or  muriate  of 
morphia  (in  which  condition  it  is  generally  used  in  medicine)  one  fourth  of  a 
grain.  It  is  a  singular  circumstance  that  this  substance,  which  is  so  poison- 
ous to  man,  has  comparatively  little  effect  upon  animals,  even  when  adminis- 
tered.in  large  doses.  The  composition  of  morphia  is  represented  by  the  formula, 
C36H20N06  +  2HO. 

Opium  also  contains,  in  addition  to  morphia,  eight  other  alkaloids,  the  prin- 
cipal of  which  are  termed  narcotine,  meconine,  and  thebaine.  They  are  all  nar- 
cotics and  poisons,  and  exist  to  some  extent  in  laudanum,  which  is  an  alco- 
holic extract  of  the  active  principles  of  opium. 

756.  The  dried  juice  of  the  common  lettuce  plant  has  considerable  resem- 
blance to  opium,  and  contains  an  active  principle  (supposed  to  be  an  alkaloid), 
called  lactucin.     It  is  this  substance  which  gives  to  lettuce,  when  freely  eaten 
as  a  salad,  its  narcotic  properties. 

757.  Quinine  and  C  i  n  c  h  o  n  i  n  e  are  the  alkaloids  which  impart  to 
Peruvian  bark  its  medicinal  virtues.     Quinine  is  a  white,  crystallized  sub- 
stance, of  an  intensely  bitter  taste.    It  is  one  of  the  most  valuable  and  reliable 
of  medicinal  agents,  and  is  generally  administered  in  the  form  of  a  sulphate. 

758.  Strychnia  and  B  r  u  c  i  a  are  extracted  from  a  variety  of  plants 
belonging  to  the  genus  strychnos,  and  especially  from  the  berries  (nux  vomica) 
of  a  small  tree  of  this  genus  growing  in  India.  These  alkaloids  are  remarkable 
for  being  the  most  powerful  of  all  vegetable  poisons — a  single  grain  of  the 
former  being  a  fatal  dose  for  an  adult  man ;  while  a  sixth  of  a  grain  has  proved 
fatal  to  a  dog  in  thirty  seconds.     Its  influence  seems  to  be  exerted  principally 
upon  the  nerves  and  spinal  marrow,  producing  violent  spasms,  which  increase 
in  frequency  and  severity  until  death.     The  celebrated  woorara  with  which 
the  natives  of  Guiana,  S.  A.,  poison  the  tips  of  their  arrows,  and  the  poison 
of  the  celebrated  Upas  tree  of  the  island  of  Java,  are  varieties  of  strychnias. 

Pure  strychnia  crystallizes  in  small,  but  exceedingly  brilliant,  colorless 
crystals,  and  is  slightly  soluble  in  water.  It  possesses  the  property  of  bitter- 
ness in  a  more  marked  degree,  probably,  than  any  other  substance,  and  its 
taste  can  be  distinctly  recognized  when  dissolved  in  600,000  times  its  weight 
of  water.  Vegetable  matters  containing  this  alkaloid  are  sometimes  employed 
for  imparting  bitterness  to  beer,  but  their  use  should  be  considered  criminal. 

759.  Among  the  other  important  alkaloids  may  be  mentioned  Nicotine,  the 
poisonous  principle  of  tobacco;  Aconitine,  or  Aconite,  extracted  from  the  plant 
"monk's  hood;"   Conicine,  prepared  from  hemlock;  Veratrine,  from  the  plant 
hellebore ;  Hyoscyamine,  from  henbane ;  and  Solanine,  from  several  species 
of  the  genus  solanum,  and  from  the  white  sprouts  of  the  potato.     All  these 
are  most  virulent  poisons,  only  inferior  in  their  action  to  strychnia  and  brucia. 

QUESTIONS. — What  is  its  composition  ?  What  is  laudanum  ?  Is  there  an  active  prin- 
ciple in  the  lettuce  plant?  What  are  quinine  and  cinchonine?  From  what  sources  are 
strychnia  and  brucia  obtained  ?  For  what  are  these  alkaloids  remarkable  ?  "What  is  said 
of  the  poisonous  influence  of  strychnia  ?  What  are  varieties  of  this  poison?  What  are 
the  other  properties  of  strychnia?  What  are  some  of  the  other  alkaloids  remarkable  for 
their  poisonous  qualities  ? 


ORGANIC    COLORING    PRINCIPLES.          457 

Among  the  alkaloids  less  injurious  in  their  action  on  the  animal  economy,  are 
Emetine,  the  medicinal  agent  of  ipecac  (ipecacuanha);  Piperine,  extracted 
from  ordinary  black  pepper ;  and  Caffeine,  or  T/ieine,  the  enlivening  principle 
in  coffee  and  tea. 

The  organic  alkaloids  are,  almost  without  exception,  precipitated  from  their 
solutions,  by  tannic  acid,  in  the  form  of  insoluble  tannates,  and  consequently 
the  most  efficient  remedies  in  cases  of  poisoning  by  them,  are  liquids  contain- 
ing tannic  acid,  such  as  decoction  of  oak-bark,  tincture  of  gall-nuts,  concen- 
trated infusion  of  green  tea,  etc.,  etc. 

The  detection  of  their  presence  in  the  animal  organism,  in  cases  of  death  by 
poisoning,  is  extremely  difficult,  strychnia  excepted,  and  the  testimony  of  the 
most  experienced  chemists  ought  only  to  be  relied  on  in  such  cases.* 

760.  Vegetable  Extracts  , — This  name  is  applied  to  a  very  large 
class  of  substances  extracted  from  plants,  which  do  not  possess  sufficiently 
marked  features,  in  a  chemical  point  of  view,  to  allow  of  their  incorporation 
with  any  of  the  more  well-defined  groups  of  organic  compounds.  Some  of 
them,  however,  possess  active  and  medicinal  properties,  as,  for  example,  the 
intensely  bitter  principle  of  wormwood,  aloes,  etc.,  the  purgative  principle  of 
the  root  of  the  rhubarb,  and  the  aromatic  bitter  of  the  hop,  sweet-flag,  etc. 
They  have  for  the  most  part  a  bitter  taste,  and  often  occur  crystallized ;  and 
are  generally  regarded  as  mixtures  of  various  vegetable  products. 


CHAPTER    XXIL 

ORGANIC     COLORING     PRINCIPLES. 

161.  THE  organic  coloring  matters,  with  the  exception  of  the  red  dye  ob- 
tained from  cochineal,  are  all  of  Vegetable  origin.  They  do  not,  as  a  class,  possess 
many  chemical  characters  in  common,  and  are  considered  under  one  general 
head,  by  reason  of  their  common  industrial  applications.  Many  of  the  most 
valuable  vegetable  coloring  agents  do  not  exist  naturally  in  plants,  but  are 
formed  by  subjecting  certain  vegetable  products  to  specific  chemical  treat- 
ment The  most  brilliant  and  splendid  of  the  vegetable  colors,  as  those  of 
flowers,  for  example,  are  exceedingly  evanescent,  and  are  generally  destroyed 
by  any  treatment  employed  to  extract  them ;  they  also  exist  in  the  vegetable 

*  A  few  years  since  a  man  was  convicted  in  Albany,  N.Y.,  of  murder,  by  the  adminis- 
tration of  tincture  of  aconite,  upon  what  was  supposed  to  be  reliable  chemical  testimony, 
but  which  was  afterward  shown  to  be  so  utterly  unreliable,  that  the  means  adopted  for 
detecting  the  poison  must  have  completely  removed  it,  if  present,  from  the  matters 
tested. 

QUESTIONS.— What  are  more  medicinal  than  poisonous?  What  are  antidotes  for  these 
poisons  ?  What  is  said  of  their  detection  in  the  system  ?  What  are  vegetable  extracts? 
What  examples  of  these  substances  f  From  what  source  do  we  derive  organic  coloring 
agents  ?  What  is  said  of  them  ? 

20 


458  OKGANIC     CHEMISTRY. 

tissue,  in  very  minute  quantities.  Coloring  matters  extracted  from  those  parts 
of  the  plant  which  are  removed  from  the  immediate  influence  of  the  light,  as 
the  wood,  bark,  etc.,  are  much  more  permanent,  but  less  brilliant. 

762.  The  art  of  dyeing  consists  in  impregnating  cloths  and  other  textures 
with  coloring  substances,  in  such  a  manner  that  the  acquired  colors  may  re- 
main permanent  under  the  common  exposure  to  which  the  articles  may  bo 
liable.     This  is  effected  by  producing  a  chemical  union  between  the  materials 
to  be  dyed  and  the  coloring  matter.     Different  fibrous  materials  present  veiy 
different  attractions  for  dye-stuffs,  and  absorb  coloring  matter  in  very  differ- 
ent proportions :  wool  appears  to  have  the  greatest  attraction ;  silk  comes 
next  to  it ;  then  cotton,  and,  lastly,  flax  and  hemp.     While  the  former,  there- 
fore, are  dyed  with  very  little  difficulty,  the  latter  can  only  be  made  to  per- 
manently combine  with  coloring  substances,  through  the  agency  of  indirect 
and  complicated  processes. 

763.  All  coloring  substances  used  in  dyeing  are  divided  into  two  classes, 
viz.,  substantive  and  adjective  colors.      A  substantive  color  is  ono  that  imparts  its 
tint  directly  to  the  substance  to  be  dyed,  without  the  intervention  of  a  third 
substance.     An  adjective  color,  on  the  contrary,  is  one  that  requires  the  inter- 
vention of  a  third  substance,  that  possesses  a  joint  attraction  for  the  coloring 
principle  and  for  the  substance  to  be  dyed. 

Most  of  the  substances  used  in  dyeing  belong  to  the  adjective  colors ;  and 
if  we  except  indigo,  there  is  scarcely  a  dye-stuff  in  extensive  use  that  imparts 
its  own  color  directly ;  and  by  far  the  greater  number  of  dyes  have  so  weak 
an  affinity  for  cotton  fabrics,  that  alone  they  communicate  no  color  sufficiently 
permanent  to  deserve  the  name  of  a  dye. 

The  intermediate  third  substance  which  is  used  to  effect  a  union  between 
the  dye  and  the  cloth,  is  called  a  mordant,  from  the  Latin  word  mordeo,  to 
bite,  from  an  idea  the  old  dyers  had  that  these  substances  bit  or  opened  a 
passage  into  the  fibers  of  the  cloth,  and  allowed  the  color  to  penetrate.  The 
action  of  a  mordant  may  be  illustrated  by  the  method  of  procedure  followed 
in  dyeing  cottons  black,  by  an  extract  of  logwood.  An  aqueous  solution  of 
logwood  is  very  deeply  colored,  but  imparts  no  permanent  dye  to  cotton.  If, 
however,  the  cotton  be  previously  impregnated  with  a  salt  of  oxyd  of  iron  (as 
copperas),  and  then  dipped  into  tho  extract  of  logwood,  the  coloring  principle 
of  the  latter,  by  reason  of  its  great  affinity  for  oxyd  of  iron,  unites  with  it,  and 
the  two  are  precipitated  upon  the  fibers  of  the  cloth  in  the  form  of  a  black  pre- 
cipitate or  dye.  A  dye  thus  effected  is  usually  a  fast  color,  since  it  is 
formed  in  and  incorporated  with  the  whole  structure  of  the  fiber  itself,  and  is 
not  merely  upon  its  surface ;  so  that  the  color  will  only  disappear  when  the 
texture  and  fiber  of  the  cloth  are  destroyed.  The  use  of  mordants,  further- 

QTTESTIONS. — In  what  does  the  art  of  dyeing  consist?  What  fibrous  substances  have  the 
greatest  attraction  for  dyes?  Into  what  two  classes  may  dyeing  principles  be  divided? 
What  are  substantive  colors  ?  What  are  adjective  colors?  To  which  class  do  the  dyes  in 
ordinary  use  generally  belong  ?  What  is  the  derivation  of  the  word  mordant  ?  Explain 
the  UM  of  mordants  ? 


ORGANIC    COLORING    PRINCIPLES.  459 

more,  adds  greatly  to  the  resources  of  the  dyer ;  because  a  single  coloring 
substance  will  impart  very  different  colors  with  different  mordants :  thus,  an 
extract  of  logwood  will  dye  with  iron,  black ;  with  a  solution  of  tin,  violet ; 
and  with  other  mordants,  all  the  shades  of  color  included  between  a  yellowish- 
white  and  a  violet,  a  lavender  and  a  purple,  or  a  slate-brown  and  a  black. 

764.  Calico-Printing . — The  general  process  of  calico-printing  is  as 
follows :  The  cloth  is  first  prepared,  by  bleaching  and  other  treatment,  to  re- 
ceive the  colors.     The  pattern  is  then  stamped  or  printed  upon  it  from  plates 
or  rollers,  which  have  been  previously  covered  with  different  mordants,  in  the 
same  way  that  ink  is  applied  to  types.     The  cloth  is  then  passed  through  a 
solution  of  dye,  when  those  parts  which  have  been  printed  with  the  mordant 
seize  upon  and  retain  the  colors.     The  cloth  is  afterward  washed,  when  all 
the  color  not  combined  with  mordant  disappears  from  its  surface,  and  the  pat- 
tern impressed  is  brought  out  with  distinctness. 

765.  The  most  important  coloring  matters  used  in  dyeing  are  as  follows: — 
Red    and    Violet    Coloring    Substances,  —  Madder  is   the 

ground-up  root  of  the  plant  rubia,  tinctorum.  Its  most  beautiful  coloring  con- 
stituent (madder  red,  Turkey  red),  called  garancine,  is  not  a  natural  product, 
but  results  from  subjecting  the  root  to  the  action  of  sulphuric  acid.  The  ac- 
tion of  the  acid  in  this  instance  is  often  cited  as  an  example  of  catalysis,  as  it 
does  not  enter  into  combination  with  the  coloring  principle  of  the  root,  but 
effects  a  change  in  it,  apparently  by  its  mere  presence. 

Madder  is  used  to  a  greater  extent  in  dyeing  and  printing  cottons  than  any 
other  substance,  and  with  different  mordants  it  furnishes  very  bright  and 
durable  reds,  yellows,  violets,  and  browns.  The  other  important  coloring 
substances  of  this  class  are  "Brazilwood,"  "  safflower"  (the  flowers  of  the  red 
caffron),  sandal- wood  ("  red-sanders"),  and  cochineal  The  last  is  a  dried 
insect,  the  COCTAS  cacti,  which  lives  upon  several  species  of  cactus,  peculiar  to 
warm  latitudes,  and  especially  to  Central  America.  It  yields  the  most  bril- 
liant scarlet  and  purple  colors. 

766.  Blue   Dyes,   Indig  o. — The  most  important  of  the  blue  dyes  is 
Indigo,  which  is  obtained  from  several  species  of  American  and  Asiatic  plants, 
particularly  from  those  belonging  to  the  genus  indigo/era.     The  juice  of  these 
plants  is  colorless,  but  when  their  leaves  are  digested  in  water,  and  allowed 
to  ferment,  a  yellow  coloring  substance  is  dissolved  out,  which,  by  exposure 
to  the  air,  gradually  becomes  blue,  and  is  deposited  from  the  solution  in  the 
form  of  a  thick  sediment.     This  washed  and  dried,  constitutes  the  indigo  of 
commerce. 

Commercial  indigo  is  far  from  pure,  and  in  addition  to  the  blue  coloring 
matter,  or  purejndigo,  it  contains  at  least  one  half  its  weight  of  foreign  sub- 
stances. Pure  indigo  is  quite  insoluble  in  every  liquid,  with  the  exception  of 

QUESTIONS. — How  do  they  increase  the  resources  of  the  dyer?  What  is  the  process 
of  calico-printing?  What  is  madder  ?  What  is  said  of  its  coloring  principles?  What  is 
cochineal?  What  colors  does  it  furnish?  What  other  dye-stuffs  furnish  red  colors? 
What  is  the  most  important  of  the  blue  dyes  ?  How  is  indigo,  prepared  ? 


460  ORGANIC    CHEMISTRY. 

fuming  sulphuric  acid  (Nordhausen),  with  which  it  forms  a  compound  quite 
soluble  in  water,  called  sulphindigotic  acid.  When  indigo  is  brought  in  con- 
tact with  water  and  dooxydizing  agents,  it  becomes  converted  into  a  soluble 
and  colorless  substance,  known  as  indigo  white,  which,  by  exposure  to  the  air, 
again  absorbs  oxygen,  and  resumes  its  blue  color.  This  circumstance  is  taken 
advantage  of  in  dyeing ;  thus,  the  indigo  is  mixed,  in  a  state  of  fine  powder, 
with  hydrate  of  lime  and  copperas,  and  the  whole  digested  in  water.  Under 
these  circumstances,  the  hydrated  protoxyd  of  iron,  resulting  from  the  action 
of  the  lime,  abstracts  oxygen  from  the  indigo,  and  reduces  it  to  a  state  of  a 
yellow  liquid  (white  indigo).  Cloths  steeped  in  this  liquid,  and  exposed  to  the 
air,  readily  acquire  a  deep  and  permanent  blue  tint,  by  the  formation  of  the 
blue,  insoluble  indigo  in  the  substance  of  the  fibers,  and  it  is  in  this  way  that 
the  fine  indigo-blue  colors  are  produced.  What  is  called  Saxon  blue,  a  brighter 
color  than  ordinary  indigo,  is  imparted  by  boiling  the  fabrics  in  sulphindigotic 
acid.  Among  other  prominent  blue  dyes,  may  be  mentioned  litmus,  which  is 
obtained  from  several  species  of  lichens,  by  treatment  with  ammonia — the 
plants  themselves  being  destitute  of  color.  Archil  and  cudbear  are  substances 
allied  to  litmus. 

767.  Yellow  Coloring  Substances . — The  most  valuable  dye- 
stuffs  of  this  class  are  fustic,  the  rasped  wood  of  a  West  Indian  tree  ;  querci- 
tron, obtained  from  the  bark  of  the  American  black  oak ;  the  berries  of  the 
buckthorn ;  annotto,  prepared  from  the  pulp  of  certain  South  American 
seeds ;  and  tumeric,  the  root  of  an  East  Indian  plant. 

768*  C  h  1  o  r  o  p  h  y  1  e  is  the  name  given  to  the  green  coloring  matter  of 
the  leaves  and  stems  of  plants.  It  exists  in  them  in  very  small  quantity,  and 
is  extracted  with  difficulty  in  a  state  of  purity.  It  appears  to  be  united  in 
the  vegetable  tissue  with  a  substance  resembling  wax,  and  is  insoluble  in 
water,  but  dissolves  in  alcohol  and  ether ;  hence  all  tinctures  in  pharmacy, 
prepared  from  the  fresh  stalks  and  leaves  of  plants,  possess  a  green  color. 
Chlorophyle  appears  only  in  those  parts  of  plants  which  are  exposed  to  the 
action  of  light ;  hence  this  agent  is  supposed  to  exercise  an  important  and 
direct  influence  on  its  formation.  Plants  grown  in  the  dark  are  nearly  des- 
titute of  color,  but  when  removed  into  the  sunlight  become  rapidly  green. 
The  red  and  yellow  colors  which  leaves  assume  in  autumn,  are  supposed  to 
be  due  to  the  decomposition  and  oxydation  of  the  chlorophyle,  and  the  for- 
mation of  an  acid  compound ;  but  the  information  we  possess  on  this  subject 
is  very  limited. 

Most  of  the  greens  used  in  dyeing  are  of  a  mineral  origin,  i.  e.,  the  salts 
of  chromium  and  of  copper. 

No  genuine  black  substantive  color  has  ever  been  obtained  from  plants. 

QUESTIONS.— What  is  said  of  the  solubility  of  indigo  ?  What  is  indigo  white  ?  How  is 
it  employed  in  dyeing?  How  is  "Saxon  blue"  imparted?  What  other  blue  dyes  are 
used  ?  Enumerate  some  of  the  principal  yellow  dye-stuffs  ?  What  is  chlorophyle  ?  What 
are  its  solvents?  What  agent  influences  its  formation?  What  is  the  character  of  the 
greens  used  in  dyeing? 


AND     BESINS.  461 


CHAPTER    XXIII. 

OILS;     FATS,     AND     RESINS. 

769.  Connection   between    Oils   and    Fats , — The  oils    and 
the  fats,  whether  of  animal  or  vegetable  origin,  are  regarded  as  belonging  to 
the  same  general  class  of  organic  substances ;  and  with  the  exception  of  the 
volatile  oils,  they  are  all  closely  allied  to  each  other  in  their  chemical  properties, 
and  are  composed  of  the  same  elements,  viz.,  carbon,  hydrogen,  and  oxygen, 
united  in  various  proportions.     As  a  class,  they  are  all,  however,  character- 
istically poor  in  oxygen,  but  rich  in  hydrogen,  and  some  few  of  the  volatile 
oils  contain  no  oxygen.     The  distinction  between  a  fat  and  an  oil  is  founded 
merely  upon  the  circumstance,  that  the  former  is  solid  at  ordinary  temper- 
atures, while  the  latter  continues  more  or  less  liquid ;  an  oil,  therefore,  may 
be  called  a  liquid  fat,  or  a  fat  a  solid  oil. 

The  fats  and  the  oils  are  all  highly  combustible,  and  burn  with  a  brilliant 
flame ;  they  are  insoluble  in  water ;  but  dissolve  with  more  or  less  readi- 
ness in  alcohol  or  ether,  and  when  brought  in  contact  with  paper  leave  a 
greasy  mark,  and  render  the  paper  translucent.  The  oily  substances  secreted 
by  plants,  are  principally  accumulated  in  the  seeds  and  coverings  of  the  fruit, 
although  no  portion  of  the  plant  is  entirely  destitute  of  them.  The  propor- 
tion existing  in  some  seeds  is  very  considerable.  Thus  flax-seed  contains 
about  20  per  cent,  of  oil,  Indian  corn  9  per  cent,  rape-seed  30  to  40  per  cent, 
while  the  seed  or  bean  which  furnishes  castor  oil  contains  as  much  as  60  per 
cent. 

770.  Division    of  the    Oils  , — All  oily  substances  are  divided  into 
two  classes,  viz.,  the  fixed  and  volatile  oils ;  the  former  when  exposed  to  the 
air  do  not  diminish  in  bulk,  while  the  latter  under  the  same  circumstances, 
readily  evaporate. 

771.  Volatile    Oils. — The  volatile  oils  do  not  possess   the  greasy 
feel  of  the  fat  oils,  and  are  almost  always  characterized  by  a  strong  aromatic 
odor,  and  a  pungent  burning  taste.     Many  of  them,  also,  are  highly  poisonous. 
With  alcohol  they  form  solutions  called  "  essences,"  and  from  this  circumstance 
the  oils  themselves  are  very  frequently  termed  "  essential."     They  also  dis- 
solve in  ether  and  acetic  acid,  and  mix  in  every  proportion  with  the  fixed  or 
fat  oils.     They  do  not,  however,  like  the  fat  oils,  form  soaps,  but  when  ex- 
posed to  the  air  they  are  frequently  changed  by  the  absorption  of  oxygen, 
and  converted  into  resins. 

These  oils  (with  the    exception  of  a  few  which  have  been  formed  ar- 

QUE8TIOX8.—  What  is  said  of  the  class  of  oils  and  fats?  What  of  their  composition? 
What  constitutes  the  difference  between  an  oil  and  a  fat?  What  are  their  properties ? 
What  is  said  of  the  distribution  of  the  vegetable  oils  ?  Into  what  two  classes  are  oily 
substances  divided?  What  are  the  characteristics  of  the  volatile  oils ?  What  are  es- 
sences ?  From  what  sources  are  the  volatile  oils  derived  ? 


462  ORGANIC    CHEMISTRY. 

tificially)  are  almost  exclusively  the  products  of  the  vegetable  kingdom,  and  are 
generally  obtained  by  distilling  the  plant  with  water ;  in  some  instances,  how- 
ever, they  are  extracted  from  the  cellular  tissue  containing  them  by  pressure, 
as  in  fresh  orange  or  lemon  peel.  The  boiling  points  of  almost  all  these  oils 
are  above  that  of  water,  but  their  vapors  are  carried  over  mechanically  in 
distillation  by  steam  at  212°  F.,  and  condense  with  it  in  the  receiver.  In 
this  way  are  obtained  the  oils  of  roses,  orange  flowers,  lemons,  lavender,  win- 
ter-green, peppermint,  and  many  others  which  in  smell  and  taste  more  or 
less  resemble  the  fresh  plants  from  which  they  are  derived.  The  greater 
portion  of  the  oil  floats  upon  the  surface  of  the  water  which  distils  over  with 
it,  but  the  latter  usually  retains  a  small  quantity  of  the  oil  in  solution,  and 
thus  acquires  its  peculiar  taste  and  odor.  Waters  thus  impregnated  are 
termed  "medicated,"  or  "perfumed  waters;"  rose-water,  lavender-water, 
peppermint- water,  etc.,  being  examples  of  this  character. 

The  various  perfumes  and  odors  which  plants  emit,  are  believed  to  be 
mainly  due  to  the  presence  of  some  one  or  more  of  the  volatile  oils  in  their 
structure,  which  gradually  evaporate,  and  diffuse  themselves  in  the  atmos- 
phere. The  quantity  of  oil,  however,  yielded  by  some  plants  which  possess  a 
marked  odor,  is  exceedingly  small — a  thousand  fresh  roses,  for  example,  af- 
fording by  distillation  less  than  two  grams  of  oil  (attar  of  roses).  In  some 
flowers,  as  the  jasmin,  the  violet,  and  the  tuber  rose,  the  oil  which  imparts 
fragrance  is,  moreover,  so  evanescent  and  delicate,  that  it  is  destroyed  by 
any  process  of  distillation,  and  in  such  cases  the  perfume  is  obtained  by  ar- 
ranging the  flowers  in  layers  between  cotton  imbued  with  some  fixed  oil ; 
which  latter  gradually  absorbs  the  volatile  oil  or  perfume  of  the  flower,  and  in 
turn  imparts  it  to  alcohol — thus  forming  an  odoriferous  essence.  Fatty  bodies 
perfumed  in  this  way  have  received  the  name  of  pomatums. 

The  volatile  oils  do  not  appear  to  be  uniformly  diffused  throughout  the 
whole  plant.  In  the  mint  and  thyme  they  reside  principally  in  the  leaves  and 
stems ;  in  the  sandal  and  cedar  trees  they  are  in  the  wood ;  in  the  rose,  vio- 
let, etc.,  in  the  leaves  of  the  flower ;  in  the  vanilla,  anise,  and  carraway,  they 
are  in  the  seed ;  and  in  the  ginger  and  sassafras  in  the  root.  Different  parts 
of  the  same  plant  not  unfrequently  furnish  different  oils ;  thus,  the  flowers 
of  the  orange-tree  furnish  one  kind,  the  leaves  another,  and  the  rind  of  the 
fruit  a  third. 

772.  Composition  of  the  Volatile  Oils . — The  volatile  oils 
differ  materially  from  each  other  both  in  their  composition  and  chemical  re- 
actions, and  are  conveniently  divided  into  three  classes,  viz.,  those  composed. 
of  carbon  and  hydrogen  only;  those  composed  of  carbon,  hydrogen,  and  oxy- 
gen ;  and  those  which  contain  in  addition  sulphur  and  nitrogen.  Most  of 
them  contain  at  least  two  proximate  principles,  one  of  which,  termed  stearop- 

QUESTIONS.—  How  are  they  obtained  ?  What  are  medicated  waters  ?  What  is  supposed 
to  be  the  origin  of  the  odors  of  plants?  What  of  the  quantity  of  volatile  oils  yielded  by 
plants?  What  are  pomatums?  Are  the  volatile  oils  uniformly  diffused  throughout 
plants  ?  Illustrate  this.  What  is  said  of  the  composition  of  the  volatile  oils  ? 


AND     RESINS.  463 

tene,  is  less  fusible  than  the  other,  and  may  be  separated  by  cold  in  the  form 
of  a  camphor-like  substance.  The  more  liquid  constituent,  termed  daioptene, 
on  the  contrary,  may  be  often  obtained  in  a  separate  condition  by  distilla- 
tion at  a  low  temperature. 

773.  Oils    composed    of    Carbon    and    Hydrogen . — This 
class  embraces  a  large  number  of  the  odoriferous  essences  of  plants,  and  fur- 
nishes some  of  the  most  remarkable  examples  of  isomeric  bodies  known  in 
chemistry.     Thus,  tho  oils  of  turpentine,  lemons,   oranges,  juniper,  copaiba, 
citron,  black  pepper,  and  many  others  which  possess  entirely  different  prop- 
erties, cotuain  exactly  tho  same   constituents,  united  in  exactly  the  same 
proportions — 100  parts  of  each  by  weight  containing  88'24  of  carbon  and 
11/76  of  oxygen.     These  proportions  are  expressed  by  the  formula  C5H4,  or 
by  some  multiple  of  it,  as  2(C5l£i).     In  addition  to  their  identity  in  chemical 
composition,  these  substances  also  agree  as  regards  their  density  and  boiling 
points.     The  fact,  however,  that  the  internal  arrangement  of  their  molecules 
or  particles  is  different,  is  strikingly  shown  by  their  diverse  influence  on  a  ray 
of  polarized  light,  some  of  them  causing  it  to  diverge  to  tho  right,  some  to 
the  left,  while  others  transmit  it  unaltered,  or  directly. 

774.  Oil    or    Spirits    of   Turpentine . — This  substance,  which 
may  be  regarded  as  the  type  or  representative  of  the  volatile  oils  containing 
only  carbon  and  hydrogen,  is  obtained  by  distilling  with  water  the  semi-fluid 
sap  or  pitch  called  in  commerce  crude  turpentine,  which  exudes  from  incisions 
made  in  the  wood  of  various  species  of  pine.     The  product  left  after  distil- 
lation is  a  resinous  solid,  which  is  popularly  termed  rosin. 

Oil  of  turpentine  is  a  thin,  colorless  liquid,  which  is  highly  inflammable, 
and  possesses  a  well-known  and  powerful  odor.  It  has  a  specific  gravity  of 
86,  and  boils  at  312°  F.  It  is  nearly  insoluble  in  water,  but  dissolves  freely 
in  alcohol  or  ether. 

Camphene,  which  is  extensively  used  in  lamps  as  a  substitute  of  oil,  is 
spirits  pf  turpentine  purified  by  repeated  distillations.  Burning  fluid  is  a  so- 
lution of  rectified  turpentine  or  camphene  in  alcohol — the  tendency  of  tho 
turpentine  to  smoke  being  diminished  by  the  addition  of  alcohol. 

Camphene  and  burning  fluid,  although  highly  inflammable,  are  not  in  them- 
selves  explosive ;  a  mixture,  however,  of  the  vapor  of  these  liquids  with  at- 
mospheric air  is  highly  explosive,  and  igniting  at  a  distance  at  the  approach 
of  the  slightest  spark  or  flame,  is  apt  to  communicate  fire  to  the  liquids  them- 
selves. Burning  fluid  being  much  more  volatile  than  camphene.  is  much  more 
dangerous,  and  its  use  as  an  illuminating  material  should  be  discountenanced 
and  forbidden.  The  explosive  character  of  the  mixture  of  its  vapor  and  air 
may  be  illustrated  without  danger  by  allowing  a  small  quantity  of  the  fluid 

QUESTIONS. — What  is  the  first  class  remarkable  for  ?  What  are  examples  of  this  fact  ? 
What  substance  is  regarded  as  the  type  of  this  class  ?  How  is  turpentine  obtained  ?  What 
is  the  residue  left  after  distillation  ?  What  are  the  properties  of  oil  of  turpentine?  What 
is  camphene  ?  What  is  burning  fluid  ?  Are  these  liquids  explosive?  Why  then  is  their 
employment  so  dangerous  ?  What  is  the  comparative  volatility  of  the  two  ?  What  ex- 
periment illustrates  tho  explosive  character  of  the  mixed  vapor  of  burning  fluid  and  air  ? 


464  ORGANIC     CHEMISTET. 

to  evaporate  in  a  tin  can  or  vial,  and  then  applying  a  lighted  taper  to  tha 
mouth.  If,  however,  the  mouth  of  the  can  be  tightly  corked,  under  these 
circumstances,  and  flame  be  applied  through  a  minute  orifice  in  the  side,  an 
explosion  of  great  violence  is  occasioned.  As  a  matter  of  ordinary  precau- 
tion in  using  these  liquids,  no  attempt  should  ever  be  made  to  fill  or  replen- 
ish lamps  that  are  lighted,  neither  should  any  vessel  containing  camphene 
or  burning  fluid  be  ever  opened  in  the  vicinity  of  a  flame. 

When  a  current  of  dry  hydrochloric  acid  gas  is  passed  through  oil  of  tur- 
pentine cooled  by  a  freezing  mixture,  a  white  solid  is  formed  which  resembles 
common  camphor  in  odor  and  appearance,  and  is  termed  artificial  camphor. 
It  is  from  this  circumstance,  probably,  that  the  term  camphene,  as  applied  to 
spirits  of  turpentine,  first  originated. 

Oil  of  turpentine  is  extensively  used  as  a  solvent  for  resins  in  the  manu- 
facture of  varnish,  in  the  preparation  of  paints,  and  to  some  extent  in  medi- 
cine. Many  substances,  also,  like  India  rubber,  etc.,  which  are  insoluble  iu 
alcohol,  readily  dissolve  in  it. 

The  other  more  important  oils  of  this  class  have  been  mentioned  above 
as  isomeric  with  oil  of  turpentine. 

775.  Essential    Oils    containing    Oxygen-— The  principal 
oils  of  this  nature  are  the  oil  of  bitter  almonds,  of  cinnamon,  of  roses,  lavender, 
tergamot,  and  peppermint.     In  this  class  the  proportions  of  the  several  con- 
stituents are  rarely  the  same  in  two  different  oils, 

Common  camphor,  prepared  by  distilling  the  wood  of  the  camphor-tree- 
(found  principally  in  Borneo  and  Japan),  is  regarded  as  a  solid  oil,  or  vola- 
tile fat  of  this  class.  It  partakes  of  the  general  properties  of  the  volatile  oils, 
may  be  distilled  without  decomposition,  and  evaporates  in  the  air  at  ordinary 
temperatures.  It  is  nearly  insoluble  in  water,  but  dissolves  freely  in  alco- 
hol, forming  what  are  termed  camphorated  spirits.  On  adding  water  to  this, 
nearly  all  the  camphor  is  thrown  down  in  a  minutely  divided  state.  Camphor 
taken  internally  in  other  than  very  small  doses,  acts  as  a  poison,  a  hundred 
grains  being  sufficient  to  cause  death.  "  When  small  pieces  of  perfectly  clean 
camphor  are  allowed  to  fall  upon  the  surface  of  pure  water,  they  rotate  and 
move  about  with  great  rapidity,  sometimes  for  several  hours  together ;  but 
if  while  the  camphor  is  rotating,  the  surface  of  the  water  be  touched  with 
any  greasy  substance  (a  glass  rod  dipped  in  turpentine  answers  best),  all 
the  floating  particles  quickly  dart  back,  and  are  instantly  deprived  of  all 
motion."  This  phenomenon  appears  to  be  due  to  the  continued  escape  of 
vapor  from  the  surfiaco  of  the  camphor. 

776.  Essential    Oils    containing    Sulphur, — The  oils    ob- 
tained by  distillation  from  black  mustard-seed,  from  assafoetida,  onions,  horse- 


What  precautions  should  always  ho  ohserred  in  the  use  of  these  liquids? 
What  is  the  reaction  between  turpentine  and  hydrochloric  acid  gas  ?  What  are  the  uses 
of  oil  of  turpentine  ?  What  are  other  important  oils  of  this  class?  What  are  the  princi- 
pal essential  oils  of  the  second  class?  What  is  common  camphor?  What  are  Its  proper- 
ties ?  What  are  examples  of  oils  of  the  third  class  ? 


OILS,     FATS,     AND    RESINS.  465 

radish,  garlic,  and  hops,  belong  to  this  class,  Many  of  them  are  character- 
ized by  nauseous  and  offensive  odors,  which  at  the  same  time  are  remarkably 
persistent,  The  bad  smell  imparted  to  the  breath  by  eating  onions  or  garlic, 
for  example,  is  occasioned  by  the  continued  presence  of  a  minute  quantity 
of  the  volatile  oils  of  these  vegetables  in  the  air  exhaled  from  the  lungs. 

The  volatile  oils  which  are  produced  by  the  destructive  distillation  of 
Vegetable  and  animal  substances,  are  as  a  class  called  empyfeumatic, 

The  essential  oils  are  mainly  used  in  the  preparation  of  essences,  perfumes, 
and  cordials.  The  latter  are  generally  made  of  brandy,  flavored  with  various 
aromatic  oils,  and  afterward  sweetened,  In  the  fermentation  of  perfumery,  a 
single  oil  or  essence  is  rarely  used  by  itself,  but  the  best  result  is  obtained  by 
a  skillful  mixture  of  the  odoriferous  principles  of  marty  plants.  Ectu  de  Cologne^ 
called  the  perfection  of  perfumery,  owes  its  excellence  to  the  application  of 
this  principle.* 

777.  Fats  , — F  i  x  e  d  Oils .— The  fixed  oils  are  mostly  destitute  of  either 
taste  or  smell ;  but  the  presence  of  certain  volatile  acids  imparts  odors  to  some 
of  them :  thus,  butter  contains  butyric  acid ;  goat's  fat,  an  odorous  acid  called 
hyrcic  acid;  while  the  nauseous  smell  of  whale  oil  is  due  to  the  presence  of 
an  acid  called  phocenic  acid,  They  do  not  evaporate  in  the  air,  are  decom- 
posed by  the  action  of  heat,  and  are  unctuous  and  greasy  in  their  feeling. 
They  dissolve  readily  in  ether  and  in  the  essential  oils,  but  are  not  soluble  to 
any  great  extent  in  alcohol,  and  are  entirely  insoluble  in  water.  All  the  oils 
have  an  attraction  for  oxygen,  and  when  exposed  to  light  and  air,  absorb  it 
rapidly,  and  give  out  carbonic  acid  and  hydrogen ;  this  action  may  be  suffi- 
ciently energetic  to  produce  ignition  (spontaneous  combustion),  especially 
When  the  oil  is  distributed  over  porous  substances,  tow,  cotton,  etc. 


*  "  Odors  resemble  Very  much  the  notes  of  a  musical  Instrument.  Some  blend  easily 
and  naturally  with  each  other,  and  produce  a  harmonious  impression,  as  it  Were,  on  the 
Sense  of  smell.  Heliotrope,  Vanilla,  orange-blossoms,  and  the  almond  blend  together  in 
this  way,  and  produce  different  degrees  of  nearly  similar  effect.  The  same  is  the  case 
with  citron,  lemon,  vervain,  and  orange-peel,  only  these  produce  a  stronger  impression,  or 
belong,  so  to  speak,  to  a  higher  octave  of  smells.  And  again,  patchouly,  sandal-wood, 
find  vitiVert  form  a  third  class,  It  requires,  of  course,  a  nice  or  Well-trained  sense  of 
(smell  to  perceive  this  harmony  of  odors,  and  to  detect  the  presence  of  a  discordant  note. 
But  it  is  by  the  skillful  admixture,  in  kind  and  quantity,  of  odors  producing  a  similar  im- 
pression, that  the  most  delicate  and  unchangeable  fragTandeS  are  manufactured.  When 
perfumes  which  strike  the  same  key  of  the  olfactory  nerve,  are  mixed  together  for  hand- 
kerchief use,  no  idea  of  a  different  scent  is  awakened  as  the  odor  dies  away  }  but  when 
they  are  not  mixed  Upon  this  principle,  perfumes  are  often  spoken  of  &s  becoming  sickly 
and  faint)  after  they  have  been  a  short  time  in  use.  A  change  of  odor  of  this  kind  ia 
never  perceived  in  genuine  ettu  de  Cologne.  Oil  of  lemons,  juniper,  and  rosemary  are 
among  those  which  are  mixed  and  blended  together  in  this  perfume.  None  of  them  can, 
however,  be  separately  distinguished  by  the  ordinary  sense  of  smell }  but  if  a  few  drops 
of  ammonia  bo  added  to  their  solution,  the  lemon  smell  usually  becomes  very  distinct.'4 

QUESTIONS. — What  are  their  peculiarities  ?  What  are  empyreumatic  oils?  For  whafc 
purposes  are  the  essential  oils  chiefly  used?  What  are  cordials?  In  what  does  the  per- 
fection of  perfumery  consist  ?  What  are  the  properties  of  the  fats  and  fixed  oils  ?  To 
what  are  their  odors  owing  ?  What  is  said  of  their  attraction  for  oxygen  ? 


466  ORGANIC     CHEMISTRY. 

778.  The  fixed  oils,  according  to  the  changes  which  they  undergo  through  tho 
absorption  of  oxygen,  are  divided  into  two  classes,  viz.,  the  drying  or  siccative 
oils,  and  the  unctuous  or  greasy  oils  |  or  those  which  become  hard  and  resinous 
by  exposure  to  the  air,  and  those  which  remain  soft  and  sticky  under  tho 
same  circumstances. 

779.  Drying   Oils .— L  i  n  s  e  e  d   Oil,  or  the  oil  obtained  by  expres- 
sion from  the  seeds  of  the  flax  plant,  is  a  representative  of  this  class ;  and  is 
the  oil  generally  used  for  mixing  with  paints,  and  in  the  manufacture  of  var- 
nishes.    Its  drying  properties,  which  especially  recommend  it  to  the  painter's 
use,  are  greatly  increased  by  boiling  it  for  some  time,  with  the  addition  of  a 
little  litharge  (protoxyd  of  lead),     As  thus  prepared,  it  is  known  as  "  boiled 
oil"  or  linseed-oil  varnish.     Oiled  silk  is  silk  to  which  successive  coats  of  puri- 
fied linseed  oil  have  been  applied.     Glazier's  putty  is  prepared  by  kneading 
together  boiled  linseed  oil  and  pulverized  chalk  (whiting). 

The  other  principal  drying  oils  are  those  extracted  from  rape-seed,  poppy- 
Beed,  the  seed  of  the  castor-oil  plant,  and  from  walnuts, 

Printer's  Ink  is  prepared  by  igniting  linseed  oil  in  suitable  vessels, 
and  allowing  it  to  burn  until  it  becomes  thoroughly  charred,  and  acquires  a 
viscid  consistency ;  it  is  then  mixed  with  a  certain  proportion  of  the  finest 
varieties  of  lamp-black. 

780.  Unctious   Oils ,— This  class  includes  the  oils  expressed  from  the 
fruit  of  the  olive  and  the  palm,  and  most  of  the  oils  and  fats  of  animal  origin. 
These  oils,  by  exposure  to  the  air,  are  liable  to  become  sour  and  rancid,  but 
they  do  not  solidify. 

781.  Composition  of  the  Fats  and  Fixed  0  i  1  s  .—Most  fats 
and  fixed  oils,  vegetable  and  animal,   are  mixtures  of  two,  and  generally 
three,  distinct  compounds,  each  of  which,  taken  singly,  has  all  the  properties 
of  a  fat  or  an  oil.     The  first  of  these  substances,  called  stearine  (from  artap, 
tallow),  is  solid  at  common  temperatures;  the  second,  okine  (from  t/lcioj1,  oil), 
is  liquid  at  common  temperatures ;  the  third,  called  margarine  (from  /ndpyapov, 
a  pearl),  on  account  of  its  pearly  appearance,  is  also  a  solid  at  common  tem- 
peratures.  All  the  fats  and  fixed  oils,  therefore,  may  be  regarded  as  mixtures 
of  the  fluid  oleine  with  the  solids  stearine  or  margarine.     If  the  solid  be  in 
larger  proportion  than  the  fluid,  then  the  compound  at  ordinary  temperatures 
is  a  solid,  and  resembles  tallqw  or  lard ;  if,  on  the  contrary,  the  fluid  consti- 
tuent prevails,  the  compound  has  the  characters  of  an  oil.     For  example, 
When  olive  oil  is  subjected  to  a  cold  of  40°  P.,  it  deposits  a  solid  fat,  mar- 
garine, which  may  be  separated  by  filtration  and  pressure ;  the  largest  por- 
tion of  the  oil,  however,  consisting  of  oleine^  retains  its  fluidity  at  a  much 
lower  temperature,     Again,  by  subjecting  mutton  tallow  to  pressure,  a  per- 

QUESTIONB. — Into  what  two  classes  are  the  fiied  oils  divided?  What  are  drying  oMs? 
"What  are  unctuous  oils  ?  What  is  a  type  of  the  drying  oils  ?  What  is  linseed  oil  ?  For 
•what  is  it  principally  used  ?  What  is  boiled  oil  ?  What  is  oiled  silk  ?  What  is  putty? 
What  are  the  other  principal  drying  oils  ?  What  is  printers1  ink  ?  What  are  included  in 
the  class  of  unctuous  oils  ?  What  is  the  composition  of  the  fixed  oils  ?  When  will  a  fatty 
body  have  the  characters  of  a  solid,  and  when  of  a  liquid  ? 


OILS,     FATS,     AND     RESINS.  467 

manently  fluid  oil,  okine,  is  extracted,  while  the  solid  which  remains  has  its 
melting  point  raised,  and  is  much  harder  than  the  original  tallow ;  it  consists 
of  stearine  and  margarine,  the  latter  of  which  melts  at  a  much  lower  tempera- 
ture than  the  former. 

Stearine,  margarine,  and  oleine  are,  however,  susceptible  of  further  analy- 
sis. They  are,  in  fact,  true  salts,  composed  of  an  organic  or  fat  acid,  united 
to  a  base ;  the  acid  being  peculiar  to  each  fatty  principle,  while  the  base  with 
which  it  is  naturally  united,  is  almost  always  the  same.  The  name  given  to 
this  base  is  glycerine,  and  it  is  regarded  as  the  hydrated  oxyd  of  a  radical, 
glyceryle.  In  stearino  the  existing  acid  is  called  stearic  acid ;  in  margarine, 
margaric  acid;  and  in  oleine,  oleic  acid.  Stearino  is  accordingly  the  stearato 
of  the  oxyd  of  glyceryle,  and  margarine  and  oleino  the  margarates  and  oleates 
of  the  oxyd  of  glyceryle.  Olive  oil  also  must  bo  described  as  a  mixture  of 
much  oleate  of  the  oxyd  of  glyceryle,  and  a  little  margarate  of  the  same  base. 

It  may  seem  singular  to  the  student  that  bodies  of  an  acid  character  should 
exist  in  fats  and  oils.  Such,  however,  is  the  case,  and  they  exhibit  acid 
properties  in  marked  degree,  such  as  reddening  litmus  paper,  neutralizing 
alkalies,  and  uniting  with  bases  to  form  salts. 

782.  Soaps. — When  fixed  fatty  or  oily  bodies  are  brought  in  contact 
with  alkaline  solutions  at  high  temperatures,  they  undergo  a  change  called 
saponiftcation ;  that  is  to  say,  the  strong  alkaline  bases  (potash  or  soda)  dis- 
place the  weak  base  glycerine,  and  unite  with  the  acids  existing  in  the  fats  or 
oils  to  form  a  homogeneous  mass,  called  soap.  Soaps,  therefore,  are  truo  salts, 
combinations  of  stearic,  margaric,  or  oleic  acid,  with  an  alkaline  base. 

Soaps  are  of  two  kinds,  hard  and  soft.  The  former  are  made  with  soda 
alone,  or  a  mixture  of  potash  and  soda,  while  the  latter  are  made  exclusively 
with  potash.  Soaps  made  with  potash  are  soft,  mainly  by  reason  of  the  deli- 
quescent character  of  the  potash,  which  is  unable  to  harden  in  the  presence 
of  any  considerable  quantity  of  water.  A  soda  soap,  on  the  contrary,  may  bo 
made  to  absorb  more  than  its  own  weight  of  water  without  becoming  fluid. 
Besides,  in  a  potash  soap,  the  glycerine,  which  before  saponification  was  com- 
bined with  the  fat  acids,  remains  mechanically  mixed  with  the  soap,  and  pro- 
motes its  fluidity.  In  the  manufacture  of  soda  soaps,  the  soap  is  obtained 
in  a  nearly  pure  state  by  the  addition  of  common  salt  to  the  watery  solution 
in  which  the  soap  is  suspended.  Soap  not  being  soluble  in  salt  water,  im- 
mediately separates  from  the  water  and  the  glycerine  contained  in  it,  and 
floats  upon  the  surface,  and  in  this  condition  may  bo  removed,  while  tho 
spent  lye,  glycerine,  and  salt  are  allowed  to  run  to  waste.  When  this  treat- 
ment is  applied  to  a  potash  soap,  another  change  is  occasioned  which  is 
purely  chemical.  The  salts  which  the  fatty  acids  form  with  potash  are  de- 
composed by  chloride  of  sodium,  and  a  mutual  interchange  of  acids  takes 

QUESTIONS. — What  is  the  constitution  of  stearine,  margarine,  and  oleine  ?  What  is 
glycerine  ?  What  are  stearic,  margaric,  and  oleic  acids  ?  What  is  understood  by  sapon- 
ification ?  What  is  a  soap  ?  When  are  soaps  hard  or  soft  ?  Why  are  potash  soaps  soft  ? 
How  are  soda  soaps  mad«  hard  ?  What  IM  the  chemical  composition  of  hard  and  soft  soaps  f 


468  ORGANIC     CHEMISTRY. 

place ;  and  hence,  when  a  potash  soap  is  mixed  with  a  solution  of  common 
salt,  both  the  soap  and  the  chloride  of  sodium  are  decomposed,  and  a  soda  soap, 
and  chloride  of  potassium  are  formed. 

Hard  soaps  are  generally  made  of  tallow,  and  are  mainly  mixtures  of  stear- 
ate  and  margarate  of  soda;  soft  soaps  are,  on  the  other  hand,  usually  made  of 
oils,  soft  fats,  and  are  mainly  oleates  of  potash,  with  glycerine  mechanically 
mixed  with  them.  Castile  soap  is  manufactured  of  olive  oil  and  soda,  its 
mottled  appearance  being  produced  by  the  addition  of  oxyd  of  iron.  Resins 
form  with  the  alkalies,  salts,  which  possess  characters  allied  to  those  of  the 
soaps,  and  in  the  manufacture  of  common  soaps,  a  quantity  of  resin  (rosin) 
is  mixed,  on  the  ground  of  economy,  with  the  fats.  Such  soaps  have  a  yel- 
lowish appearance,  and  are  known  as  yellow  soaps. 

Soaps,  by  reason  of  their  strong  attraction  for  water,  always  retain  a  con- 
siderable quantity  of  it  in  their  composition ;  the  proportion  In  the  best  hard 
soaps  varying  from  25  to  30  per  cent.  It  is  possible,  however,  to  prepare  a 
solid  soap  containing  more  than  its  own  weight  of  water.  Such  soaps  look 
well  when  fresh,  but  contract  greatly  on  drying.  Dealers  generally  store 
their  soap  in  cellars  and  damp  places,  since  it  is  for  their  interest  to  sell  as 
large  a  proportion  of  combined  water  as  possible. 

Soap  is  freely  soluble  in  pure  water,  but  in  salt  water,  and  all  other  saline 
solutions,  it  is  insoluble;  soap  made  from  the  oil  extracted  from  the  cocoa-nutT 
is,  however,  an  exception  to  this  rule,  as  it  dissolves  freely  in  strong  brine, 
and  is  hence  much  used  as  marine  soap.  When  a  solution  of  a  soap  having 
an  alkaline  base  is  mixed  with  a  salt  of  any  other  base,  double  decomposition 
ensues,  and  an  insoluble  compound  of  the  fatty  acids  with  tho  earthy  or  me- 
tallic bases  is  precipitated.  The  salts  of  lime  and  magnesia  contained  in  nat- 
ural waters  act  in  this  manner,  and  their  presence  in  a  water  renders  it  hard 
and  unfit  for  washing.*  The  slimy  scum  which  is  formed  by  the  addition  of 
soap  to  such  water,  is  a  compound  of  tho  fatty  acids  with  lime  or  magnesia. 
The  strong  acids  decompose  both  soap  and  fats,  uniting  to  their  bases,  and 
setting  free  the  fatty  acids. 

Ammonia  acts  far  more  feebly  upon  fatty  bodies  than  either  potash  or  soda, 

183.  Cleansing  Properties  of  Soaps. — The  detergent,  or 
cleansing  action  of  soap  depends  entirely  upon  its  alkaline  constituents. 
The  impurities  upon  the  skin,  or  on  articles  of  clothing,  always  contain  a 
certain  proportion  of  oily  matter,  which  exuding  from  the  pores  of  the  sys- 

*  The  hardness  of  a  water  maybe  easily  tested  by  adding  to  it  a  few  drops  of  a  solution 
of  soap  in  alcohol  (tincture  of  soap).  If  the  water  remains  clear,,  it  is  perfectly  soft ;  if  it 
becomes  cloudy,  it  may  be  regarded  as  hard— the  degree  of  hardness  being  proportioned 
to  the  degree  of  cloudiness  occasioned. 

QUESTIONS.— What  is  said  of  the  use  of  resin  in  the  mannfactore  of  soaps?  What 
percentage  of  water  is  contained  in  soap  ?  "Why  will  not  soaps  wash  in  salt  water  ? 
When  a  solution  of  an  alkaline  soap  is  brought  in  contact  with  an  earthy  or  metalfic  base, 
what  happens  ?  Why  will  not  soaps  wash  in  hard  water  ?  What  effect  hare  acids  upon 
soaps  and  fats?  What  is  the  action  of  ammonia?  To  what  are  the  cleansing  properties 
of  soaps  due? 


AND     RESINS.  469 

tern,  and  existing  in  the  perspiration,  acts  as  a  cementing  agent  with  what- 
ever dust  or  dirt  is  brought  in  contact  with  it.  Water  alone,  by  reason  of 
its  total  want  of  affinity  for  all  fatty  or  oily  substances,  is  unable  to  dissolve 
these  impurities,  and  effect  their  removal.  An  alkali,  on  the  contrary,  readily 
unites  with  the  greasy  and  organic  matter,  and  renders  it  soluble. 

When  a  soap  is  dissolved  in  water,  a  portion  of  its  alkali  is  set  free  (by 
the  substitution  of  water  as  a  base),  and  uniting  with  the  impurities  intended 
to  be  removed,  partially  saponifies  them,  and  renders  them  soluble  or  mis- 
cible  with  water.  The  fatty  acids  also,  by  their  lubricity,  cause  the  dissolved 
matter  to  wash  away  more  easily.  An  alkali  used  alone  would  act  more 
powerfully  than  any  soap  as  a  detergent,  but  it  would  tend  to  destroy  the 
texture  of  the  organic  substance  to  which  it  was  applied,  and  also  to  remove 
the  colors  of  dyed  fabrica  When  used  in  the  form  of  soap,  its  solvent  powers 
are  partially  neutralized.  In  washing  the  surface  of  the  body  with  soap,  its 
alkaline  constituent  not  only  effects  the  removal  of  the  dirt,  but  also  dissolves 
off  the  cuticle,  or  outer  layer  of  the  skin  itself,  which  being  mainly  composed 
of  albumen,  is  soluble  in  alkaline  solutions ;  and  thus  every  washing  of  the 
skin  leaves  a  new  and  sensitive  surface. 

What  are  called  washing  fluids  are  merely  solutions  of  the  caustic  alkalies. 
They  facilitate  washing  simply  by  providing  an  excess  of  alkali.  When  the 
water  employed  in  washing  is  somewhat  hard,  their  use  in  moderate  quan- 
tity may  be  recommended,  as  they  precipitate  the  earthy  gaits  present  in  the 
water,  and  render  it  soft.  An  excess  of  free  alkali,  however,  in  washing 
always  tends  to  injure  fibers  and  occasion  them  to  shrink.  Camphene  (recti- 
fied spirits  of  turpentine)  is  also  employed  to  some  extent  in  washing ;  it 
acts  as  a  solvent  for  grease,  and  its  use  is  in  no  way  injurious  to  fabrics. 

784.  Stearic  Acid  is  a  milk-white  solid,  inodorous,  tasteless,  and 
highly  crystalline.  Mixed  with  some  marganc  acid,  it  is  extensively  used 
for  the  manufacture  of  candles,  which  are  sold  under  the  name  of  stearine, 
or  adamantine  candles.  It  is  obtained  for  this  purpose  mainly  from  tallow 
and  lard,  by  heating  them  by  steam  in  vats  with  a  mixture  of  lime  and  water. 
Under  these  circumstances  an  insoluble  lime  soap  is  formed,  while  the  gly- 
cerine remains  dissolved  in  the  water.  This  soap  is  then  heated  separately 
with  dilute  sulphuric  acid,  which  unites  with  the  lime  to  form  an  insoluble 
sulphate,  and  leaves  the  fat  acids  in  a  separate  state  floating  opon  the  sur- 
face of  the  liquid.  These,  when  cold,  are  submitted  to  pressure,  by  which 
the  oleic  acid  is  removed,  and  the  stearic  and  margaric  acids  left  in  a  nearly 
pure  condition.  Stearic  acid  melts  at  a  temperature  of  158°  F.  Margaric 
acid  closely  resembles  stearic  acid,  but  is  more  fusible,  melting  at  a  tempe- 
rature of  about  140°  F.  Lard  oil,  extracted  from  lard  by  pressure,  is  nearly 
pure  oleine. 

QUESTIONS. — Why  will  not  pure  water  answer  as  a  detergent  ?  How  does  a  soap  act  in 
removing  dirt  ?  Why  do  we  not  use  alkalies  alone  as  detergents?  What  are  washing 
fluids  ?  What  is  their  use  ?  What  is  the  appearance  of  stearic  acid  ?  What  are  stearine 
candles?  How  is  stearic  acid  prepared?  What  is  said  of  margaric  acid?  What  is  an 
example  of  nearly  pure  oleine  ? 


470  ORGANIC    CHEMISTRY. 

"We  apply  the  term  lard  to  those  animal  fats  which  at  common,  tempera- 
tures have  a  soft  and  unctuous  consistency,  and  tallow  to  those  which  remain 
hard  ;  the  only  difference  between  the  two  is  in  the  proportion  of  the  constitu- 
ent, oleine,  which  is  greater  in  lard  than  in  tallow.  The  fats  of  carnivorous  ani- 
mals and  of  birds  are  soft  (lard),  while  that  of  ruminating  animals  is. hard 
(tallow).  Fish,  or  train  oil,  is  obtained  from  the  blubber  of  whales,  seals, 
and  various  fishes.  Spermaceti  is  a  peculiar  fat  found  in  cavities  of  the  head 
of  the  right  whale.  It  differs  from  other  animal  fats,  inasmuch  as  it  does 
not  contain  glycerine,  but  another  basic  substance  termed  ethal,  while  the 
fat  acid  combined  with  it  is  called  ethalic  acid. 

Olive  oil,  or  the  sweet  oil  of  commerce,  is  obtained  by  pressure  from  the 
fruit  of  the  olive-tree.  It  is  composed  chiefly  of  oleine  and  a  little  marga- 
rine. Palm  oil,  which  within  a  comparatively  few  years  has  become  an  im- 
portant article  of  commerce,  is  obtained  principally  on  the  West  Coast  of 
Africa,  in  immense  quantities,  from  the  fruit  of  a  species  of  palm-tree.  It 
has,  when  fresh,  a  deep  orange-red  tint,  and  an  agreeable  odor,  and  at  ordi- 
nary temperatures  has  the  consistency  of  butter.  It  consists  of  a  fluid  fat, 
oleine,  and  a  cry  stall  izable  solid,  resembling  margarine,  which  has  been  called 
palmatine,  and  which  consists  of  palmatic  acid  and  glycerine. 

Human  fat  contains  palmatine,  margarine,  and  some  oleine.* 

784  Glycerine  is  a  sweet,  syrupy  liquid,  not  volatile,  arid  readily  so- 
luble in  water  and  alcohol.  Until  within  the  last  few  years  its  properties 
have  been  overlooked,  and  it  was  not  regarded  as  applicable  to  any  useful 
purpose.  In  its  solvent  power,  however,  with  respect  to  the  metalloids,  the 
salts,  and  the  neutral  organic  bodies,  it  equals,  if  not  surpasses,  that  of  alco- 
hol or  water.  Exposed  to  the  air,  it  does  not  become  rancid,  or  readily 
dry  up.  It  also  possesses  remarkable  antiseptic  properties,  and  preserves 
animal  tissues  immersed  in  it  in  ah1  their  natural  colors.  It  has  recently 
been  extensively  applied  in  medicine  for  the  dressing  of  wounds,  burns,  and 
sores,  as  a  solvent  for  various  medicinal  principles  in  the  place  of  alcohol  or 
oils,  and  as  a  remedy  for  insect  bites.  It  may  be  obtained  in  a  nearly  pure 
state  by  saponifying  tallow  with  lime,  and  by  various  other  processes. 

785.  When  glycerine  is  strongly  heated  it  is  decomposed,  and  evolves  a 
volatile,  extremely  pungent  substance  termed  ocroleine,  which  causes  lachry- 
matioru  The  formation  of  this  body  occasions  the  disagreeable  smell  noticed 


*  Bodies  buried  in  churchyards,  or  submerged  for  a  long  time  in  water,  are  sometimes 
entirely  converted  into  a  peculiar  substance  resembling  fat,  termed  odipocere.  In  the 
removal  of  the  extensive  cemetery,  les  Innocens,  in  Paris,  in  1767,  more  than  1503  bodies, 
which  had  been  interred  in  one  pit,  were  found  in  this  condition,  and  were  to  Borne  extent 
disposed  of  to  soap-boilers,  and  manufactured  into  soap. 

QUESTIONS.— How  does  lard  differ  from  tallow  ?  From  what  sources  are  lard  and  tal- 
low obtained  ?  From  what  sources  is  train  oil  obtained  ?  What  is  spermaceti  ?  What  is 
olive  oil?  What  is  palm  oil  ?  What  are  its  constituents  ?  What  does  human  fat  consist 
of?  What  are  the  properties  of  glycerine  ?  What  is  said  of  its  solvent  powers  ?  What 
is  acroleine  ? 


OILS,     FATS,     AND     KESINS.  471 

during  the  smoldering  of  a  candle-wick,  and  it  may  be  also  perceived  dur- 
ing the  imperfect  combustion  of  all  kinds  of  fats. 

786.  Wax  . — The  term  wax  is  applied  by  chemists  to  substances  derived 
from  various  sources,  which  resemble  in  composition  and  properties  tho  wax 
forming  the  solid  portion  of  honeycomb,     It  has  long  been  a  matter  of  dis- 
pute among  naturalists,  whether  tho  bee  merely  collects  the  wax  formed  by 
plants,  or  secretes  (manufactures)  it  from  honey  (sugar)  in  the  tissues  of  its 
body.     The  latter  view  of  the  case  is  now  generally  adopted.     The  constitu- 
ents of  wax  are  the  same  as  those  of  the  fata  and  oils,  viz.,  carbon,  hydro- 
gen, and  oxygen — the  formula  for  bees-wax  being  034113402- 

Bees-wax,  in  its  natural  state,  is  yellow,  but  is  bleached  white  (white  wax) 
by  exposure  in  thin  ribbons  to  the  action  of  light,  air,  and  moisture.  It 
fuses  at  a  temperature  of  150°,  and  is  soluble  in  ether  and  spirits  of  tur- 
pentine. When  heated  with  boiling  alcohol,  it  separates  into  different  proxi- 
mate principles,  myricine  and  cerine,  the  last  of  which  separates"  from  the 
alcohol  on  cooling  in  delicate  needle-like  crystals.  It  is  doubtful  whether 
these  bodies  are  susceptible  of  saponification.  Wax  digested  with  oils,  forms 
a  kind  of  ointment  termed  cerates.  Wax  also  occurs  i;i  all  plants,  especially 
in  the  glossy  coating  or  varnish  observed  upon  the  surface  of  leaves  and  the 
skins  of  fruit  (as  in  the  skin  of  tho  apple).  From  some  species  of  plants  it 
is  obtained  in  sufficient  quantities  to  constitute  an  article  of  commerce  •  as 
the  baybernj  tallow^  or  myrica  wax,  which  is  obtained  by  steeping  the  leaves 
nnd  fruit  of  a  species  of  myrtle  in  hot  water.  The  great  demand  for  wax  is 
for  the  manufacture  of  candles,  which  are  first  molded  by  the  hand  and  then 
shaped  by  rolling  upon  a  hard  surface.  Wax  burns  with  a  beautiful  clear 
light,  and  is  the  most  expensive  material  employed  for  illumination. 

787.  Resins , — Resinous  substances  are  found  in  greater  or  less  abun- 
dance in  almost  all  plants,  and  are  regarded  as  tho  products  of  the  oxyda- 
lion  of  the  essential  oils.     Many  of  them  exude  naturally  from  fissures  or 
incisions  in  tho  bark  or  wood.     They  are-  all  insoluble  in  water,  but  dissolve 
readily  in  alcohol,  ether,  and  tho  essential  oils.     When  pure  and  free  from 
essential  oils,  they  have  no  odor  except  when  rubbed  or  heated.     They  are 
also  good  insulators  of  electricity,  and  become  electric  by  friction.     In  color 
they  are  pale  brown  or  red. 

788.  Colophony  . — Common  pine  resin  (msm),  also  termed  colophony, 
which  is  tho  residue  left  after  the  distillation  of  crude  turpentine,  is  a  good 
example  of  this  class  of  resins.     It  contains  two  distinct  bodies  having  acid 
properties,  called  pinic  and  silvic  acids,  which  may  be  separated  from  each 
other  by  treatment  with  alcohol.     These  acids  unite  with  bases  to  form  salts, 
and  their  combinations  with  tho  alkalies  are  true  soaps  (rosin  soaps).     Rosin 

QTTKSTIONS. — What  is  wax  ?  "What  is  the  origin  of  bees-wax  ?  Into  what  two  principles 
may  wax  be  divided  ?  How  is  white  wax  formed  ?  Under  what  circumstances  is  wax 
found  in  vegetables  ?  What  is  bayberry  tallow  ?  What  is  said  of  the  occurrence  of  resins  ? 
What  are  their  general  properties?  What  is  a  characteristic  example  of  this  class  of 
bodies  ?  How  is  rosin  obtained  ?  What  is  its  chemical  name  ?  What  is  its  composition  ? 
What  is  pine  oil  ? 


472  ORGANIC     CHEMISTRY. 

yields  by  distillation  a  great  variety  of  products,  the  most  important  of  which 
is  a  fixed  oil,  which  is  extensively  used  for  lubrication  and  somewhat  for 
illuminating  purposes,  under  the  name  of  sylvic,  or  pine  oil,  Rosin  is  extremely 
brittle,  and  may  be  easily  reduced  to  a  fine  powder,  in  which  condition  it  is 
used  to  increase  friction,  as  it  renders  the  surfaces  to  which  it  IB  applied 
rough  and  adhesive;  its  application  to  the  bows  of  violins,  and  to  the 
cords  of  clock  weights  to  prevent  their  slipping,  are  familiar  illustrative  ex- 
amples. Rosin  ignited  for  a  time  and  then  extinguished,  is  converted  into 
a  soft,  black,  pitchy  substance,  generally  known  as  ship's  pitch,  or  shoemaker's 
wax. 

789.  Lac. — This  important  resinous  substance,  which  is  exported  from 
the  East  Indies  to  the  extent  of  half  a  million  of  pounds  annually,  is  pro- 
duced by  the  puncture  of  the  bark  of  certain  species  of  trees  by  an  insect, 
and  by  its  elaboration  of  the  exuding  juice  into  cells  for  its  eggs.  It  occurs 
in  commerce  under  three  forms.  Thus  the  broken  off  twigs  of  the  trees 
incrusted  with  lac  constitute  stick  lac,  removed  from  the  twigs  it  is  sted  lac, 
and  when  refined  by  melting  and  straining  it  is  shellac.  Stick  lac,  owing 
to  the  presence  of  the  dead  insect  in  its  structure,  yields  by  proper  treatment 
a  dye  which  is  nearly,  or  quite  as  bright  as  that  obtained  from  cochineal. 
Lac  is  also  extensively  employed  in  the  preparation  of  varnishes,  in  the 
manufacture  of  hats  (for  stiffening  the  hat  body),  and  as  the  principal  ingre- 
dient in  sealing-wax.*  "What  is  called  gold  varnish  is  a  solution  of  shellac 
in  alcohol,  colored  yellow  by  gamboge  and  tumcric. 

Mastic,  "  Dragon's  blood,"  so  called  from  its  deep  red  color,  and  Sandarac, 
are  also  resins  largely  employed  for  the  manufacture  of  Varnishes.  Copal 
is  exceedingly  hard,  and  of  a  light  yellow  color ;  it  differs  from  the  other 
resins  in  being  almost  insoluble  in  alcohol  and  the  essential  oils.  Copal  var- 
nish is  made  by  first  fusing  the  resin,  and  then  adding  spirits  of  turpentine 
and  linseed  oil.  Gum  guiacum,  much  used  in  medicine,  is  the  product  of  the 
lignum-vitse  tree  of  the  West  Indies. 

190.  Amber . — The  source  of  amber  was  for  a  long  time  uncertain  ;  by 
some  it  was  supposed  to  be  a  carbonaceous  mineral,  but  it  is  now  Univer- 
sally considered  to  be  a  fossil  vegetable  resin,  the  product  of  a  species  of 
the  pine  family  now  extinct.  Whenever  found  in  its  natural  location  in 
the  earth,  it  is  associated  with  carbonized  wood  or  coal.  It  is  chiefly  found 
on  the  shores  of  the  Baltic  Sea,  and  is  apparently  washed  out  of  the  sand  by 
the  waves.  The  largest  block  known  is  in  the  Royal  Museum  of  Berlin, 


*  Common  red  sealing-wax  is  usually  made  of  4  parts  of  lac,  1  to  \\  of  Venice  turpen- 
tine, and  3  parts  of  vermilion,  the  whole  being  fused  together  by  a  moderate  heat.  By 
substituting  different  coloring  principles,  different  colored  Varieties  of  (sealing-wax  are 
prepared. 


QITESTIOXS.— What  is  shoemaker's  wax  ?  "What  is  lac  f  What  are  its  Varieties  f  What 
are  its  uses?  What  other  resins  are  largely  employed  for  Varnishes  ?  What  is  said  of 
copal  ?  What  is  amber  ?  Where  is  it  principally  found  ? 


OILS,     FATS,     AND     RESINS.  473 

and  weighs  13  Ibs.  Amber  often  contains  insects  so  perfectly  and  delicately 
preserved,  that  they  could  not  have  become  incorporated  in  the  mass,  ex- 
cept it  was  once  in  the  condition  of  a  volatile  oil  or  a  semi-fluid  resin.  It 
is  the  hardest  of  all  the  resins,  has  a  yellowish  color,  and  is  slightly  acted 
upon  by  alcohol  or  the  essential  oils.  Being  commonly  translucent,  and  sus- 
ceptible of  a  fine  polish,  it  is  often  made  into  ornaments,  such  as  necklaces, 
the  mouth-pieces  of  pipes,  etc.  The  beautiful  black  varnish  used  by  coach- 
makers  is  a  very  carefully -prepared  compound  of  amber,  asphaltum,  linseed 
oil,  and  turpentine.  Amber  is  a  compound  of  several  resinous  principles,  and 
a  p3culiar  acid  called  succinic  acid. 

791.  Balsams  , — Many  resinous  substances,  as  they  exude  from  trees 
or  shrubs,  are  mixed  with  an  essential  oil,  which  either  evaporates  on  com- 
ing in  contact  with  the  air,  or  is  converted  into  resin  by  the  absorption  of 
oxygen.  Such  mixtures  of  resins  and  essential  oils  are  called  balsams.  The 
crude  turpentine  or  pitch  which  exudes  from  the  pine  is  an  example  of  a 
true  balsam,  since  by  distillation  it  is  separated  into  a  volatile  oil — turpen- 
tine and  hard  resin.  Among  the  other  important  commercial  balsams  are 
*'  Canada  balsam,"  the  product  of  the  silver  fir,  "  Venice  turpentine,"  the  pro- 
duct of  a  species  of  larch,  Copaiba  balsam,  balsam  Tolu,  Peru,  and  gum  ben- 
zoin. The  three  former  are  merely  natural  varnishes,  i.  e.,  resins  dissolved  in 
volatile  oils ;  the  latter  contain  in  addition  an  acid  principle.  This  acid  in 
gum  benzoin  is  called  benzoic  acid,  and  is  chemically  interesting  by  reason 
of  the  number  and  marked  character  of  the  salts  which  it  forms  with  bases. 
Benzoic  acid  may  also  be  obtained  artificially  as  a  product  of  the  oxydation. 
of  the  oil  of  bitter  almonds.  The  gum  itself  is  very  fragrant,  and  is  the  chief 
ingredient  in  the  incense  burnt  in  Catholic  churches. 

192.  Gum  Resins  — This  term  is  applied  to  a  class  of  vegetable  pro- 
ducts which  contain  in  addition  to  a  resin  and  an  essential  oil,  a  portion  of 
gum  and  various  other  extractive  matters.  "When  they  first  escape  from  in- 
cisions in  the  stems  or  branches  of  trees  and  shrubs,  they  are  fluid  and  of  a 
light  color,  but  gradually  harden,  and  become  of  a  deeper  hue.  Most  of 
them  also  possess  a  strong  odor,  and  a  warm,  acrid  taste.  Owing  to  their 
mixed  composition,  they  are  not  perfectly  soluble  in  either  water  or  abso- 
lute alcohol,  but  are  completely  dissolved  by  proof  spirit.  This  class  of 
substances  includes  many  valuable  medicinal  principles,  such  as  myrrh,  asa- 
foetida,  aloes,  gamboge  (the  well-known  coloring  agent),  gcammony,  and 
others.  Opium  is  also  included  in  this  class. 

793.  V  a  r  n  i  s  h  is  a  solution  of  a  resinous  substance  which  is  applied  to 
the  surface  of  bodies  for  the  purpose  of  investing  them  with  a  hard,  transpa- 
rent, lustrous  coating.  When  the  solvent  for  the  resin  is  alcohol,  the  pro- 
duct is  termed  spirit  varnish,  and  when  an  essential  or  dyeing  oil,  oil  var- 

QUESTIONS.— What  are  its  properties  and  uses  ?  What  is  said  of  its  chemical  composi- 
tion ?  What  are  balsams  ?  "What  are  examples  ?  What  is  said  of  gum  benzoin  ?  What 
are  gum  resins  ?  What  are  their  properties  ?  What  are  some  of  the  principal  bodies  of 
this  class  ?  What  is  varnish  ? 


474  ORGANIC     CHEMISTRY. 

nish.     French  polish  is  an  alcoholic  solution  of  shellac,  -with  a  little  oil 
added. 

7  94.  The  Elastic  Gums . — Two  varieties  of  this  class  only  are  known 
in  commerce — caoutchouc  or  India-rubber,  and  gutta  percha.  There  are, 
however,  several  other  vegetable  products  of  a  like  character  which  have  not 
been  made  practically  available. 

Caoutchouc  is  obtained  from  the  milky  juice  afforded  by  several  species  of 
tropical  plants,  in  which  it  exists  in  the  form  of  small  globules  suspended  in 
an  aqueous  liquid,  precisely  in  the  same  manner  as  the  little  globules  of 
oily  matter  float  about  in  milk.  When  the  juice  is  exposed  to  the  air,  the 
caoutchouc  gradually  separates,  and  hardens  into  a  white  elastic  mass,  inso- 
luble in  water  or  alcohol.  The  usual  black  color  of  India-rubber  is  a  discol- 
oration occasioned  by  the  smoke  of  the  fires  over  which  the  fresh  product  is 
dried.  The  addition  of  a  little  ammonia  to  the  milky  juice  temporarily  pre- 
vents the  separation  of  the  caoutchouc,  and  under  these  circumstances  the 
caoutchouc  may  be  exported  in  tightly-corked  bottles  in  its  natural  condition. 
A  short  exposure  to  the  air,  however,  soon  occasions  its  separation  as  a 
milk-white  solid. 

The  physical  properties  of  caoutchouc  are  well  known.  It  is  soluble  in 
pure  ether,  naphtha,  benzole,  oil  of  turpentine,  and  the  bi-sulphide  of  carbon. 
At  a  temperature  a  little  above  the  boiling  point  of  water  it  melts,  but  does 
not  regain  its  solid,  elastic  state  on  cooling.  Caoutchouc  contains  no  oxygen, 
and  is  composed  of  carbon  and  hydrogen  united  probably  in  equal  propor- 
tions. 

When  caoutchouc  is  heated  in  connection  with  sulphur,  it  incorporates  a 
quantity  of  the  sulphur  into  its  structure,  and  undergoes  a  remarkable  change, 
becoming  what  is  called  vulcanized  rubber.  In  this  condition  it  is  less  liable 
to  be  hardened  by  cold  or  softened  by  heat,  and  is  also  rendered  more  elas- 
tic and  insoluble  in  ether  and  the  essential  oils.  It  is  from  this  material  that 
almost  all  India-rubber  goods  are  now  fabricated.  Vulcanized  rubber,  by 
mixture  with  a  proportion  of  bituminous  or  pitchy  matter,  and  some  earthy 
material  like  magnesia,  may  be  converted  into  a  hard,  black,  lustrous  sub- 
stance, which  works  like  ivory,  and  is  extensively  used  for  the  manufacture 
of  combs,  pencil-cases,  knife-handles,  etc. 

FiG.  232.  AS  caoutchouc  is  unaffected  by  most  chemical 

agents,  and  is  at  the  same  time  supple  and  flexible, 
"~"~  it  admits  of  many  useful  applications  in  practical 
chemistry.     Short  flexible  tubes  for  the  connection 


of  apparatus  are  easily  formed  by  wrapping  a  piece  of  sheet  rubber  over  a 
glass  tube  or  rod  (see  Fig.  232),  and  cutting  off  the  superfluous  portions  with 
a  pair  of  scissors  (see  Fig.  233).  On  pressing  together  and  gently  warming 

QUESTIONS. —What  substances  arc  included  in  the  class  of  elastic  gums  ?  From  what 
source  is  caoutchouc  obtained  ?  What  is  its  natural  condition  and  color  ?  What  is  said 
of  its  solubility?  What  is  its  chemical  composition?  What  is  vulcanized  rubber? 
What  effect  has  the  addition  of  sulphur  upon  the  qualities  of  rubber  ? 


NUTRITION   AND   GROWTH   OF   PLANTS.        475 

the  fresh-cut  edges,  they  cohere,  and  form  a  tube,  FIG.  233. 

which  firmly  tied  at  both  ends,  binds  two  separate 
glass  tubes  air-tight  with  each  other.  (See  Fig. 
234.) 

Most  of  the  caoutchouc  at  present  used  is  obtained 
from  the  country  bordering  on  the  banks  of  the 
Amazon,  South  America. 

795.  Gutta  Pe  re  ha.  —This  substance,  like 
caoutchouc,  is  obtained  from  the  milky  juice  which 
exudes  from  several  species  of  trees  peculiar  to 
Southern  Asia.  At  ordinary  temperatures  it  is 
slightly  elastic  and  as  tough  and  hard  as  wood ;  but 
when  immersed  in  warm  water,  it  softens  and  be- 
comes highly  plastic  and  ductile,  regaining  its  original  hardness  on  cooling. 
This  property  allows  it  to  be  molded  with  great  facility  into  many  articles  of 
utility  and  ornament.  Gutta  percha  possesses  a  dirty  white  color,  and  a  pe- 
culiar leathery  smell ;  it  is  highly  inflammable,  and  is  insoluble  in  water  or 
alcohol,  but  dissolves  in  ether,  the  essential  oils,  chloroform,  and  bi-sulphuret 
of  carbon. 


FIG.  234. 


CHAPTER    XXIV. 

THE     NUTRITION     AND     GROWTH     OF     PLANTS. 

796.  Elements  of  Vegetable  Organization,  —  The  ele- 
ments which  constitute  the  organic  structure  of  plants  are,  as  has  been  already 
stated,  carbon,  hydrogen,  oxygen,  and  nitrogen — the  three  former  being 
largely  in  excess. 

In  addition  to  these,  all  plants  contain  various  inorganic,  or  rather  mineral 
substances,  the  presence  of  which  in  their  structure  is  essential  to  a  healthy 
growth  and  organization.  The  number  and  the  nature  of  these  mineral 
substances  are  ascertained  by  analysis  of  the  ashes  (the  incombustible  part) 
which  plants  yield  by  combustion.  They  are  mainly  potassa,  soda,  lime,  mag- 
nesia, and  sesquioxyd  of  iron,  combined  with  carbonic  acid,  sulphuric  acid,  silicic 
acid,  phosphoric  acid,  and  various  chlorides.  The  ashes  of  all  cultivated  plants 
contain  these  mineral  substances ;  but  the  proportions  vary  with  the  nature 
of  the  plant.  Thus  silica  abounds  in  the  stalks  of  grains  and  grasses,  phos- 
phoric acid  in  the  seeds  of  grain-bearing  plants,  potash  in  leaves  and  many 
edible  roots,  and  lime  in  leguminous  plants,  peas,  beans,  etc. 

QUESTIONS. — What  is  gutta  percha  ?  What  are  its  properties  ?  "What  are  the  elements 
that  make  up  the  organic  structure  of  plants?  What  other  substances  are  regarded  as 
essential  constituents  ?  How  may  we  ascertain  the  nature  of  the  mineral  substances 
which  enter  into  the  composition  of  plants  ?  Do  all  plants  contain  the  same  mineral  con- 
stituents ?  Illustrate  this. 


476  ORGANIC     CHEMISTRY. 

The  mineral  constituents  of  plants  do  not  necessarily  exist  in  the  living 
tissues  in  the  same  form  as  in  the  ashes  atibrded  by  the  combustion  of  these 
tissues.  Thus,  sulphur  and  phosphorus  appear  to  exist  uncombined  in  albu- 
minous matter,  while  the  earthy  bases  are  very  generally  united  in  the  struc- 
ture of  plants  with  vegetable  acids.  In  the  process  of  combustion,  however, 
the  latter  become  converted  into  carbonates,  while  the  sulphur  and  the  phos- 
phorus unite  with  oxygen  to  form  acids,  which  in  turn  generally  unite  with 
one  of  the  bases  present  to  form  salts  characteristic  of  these  elements. 

797.  Sources    of    Nutriment    to   Plants  .—Plants  obtain  their 
nutriment  partially  by  their  leaves  and  partly  by  their  roots.     The  former  are 
furnished  with  a  great  number  of  microscopic  pores,  or  stomata*  while  in 
the  latter  the  nutritious  matter  penetrates  the  cell-walls  of  the  rootlets  by 
the  force  of  endosmosis.     It  must  be,  therefore,  evident  that  the  plant  can 
only  absorb  its  nutriment  in  a  liquid  or  aeriform  condition. 

798.  The  hydrogen  and  oxygen  which  plants  contain  are  derived  princi- 
pally from  water  which  is  absorbed  as  a  liquid  by  the  roots  from  the  earth, 
or  as  vapor,  from  the  air,  by  the  leaves.     The  substances  which  make  up  the 
great  bulk  of  the  structure  of  all  plants,  viz.,  cellulose,  lignine,  starch,  sugar, 
and  gum,  contain  oxygen  and  hydrogen  in  exactly  the  same  proportions  as 
they  exist  in  water,  and  they  may  in  fact  be  regarded  as  merely  compounds 
of  carbon  (their  other  constituent  element)  with  water.     The  presence  of 
water  in  a  liquid  condition  in  the  plant  is,  moreover,  indispensable  to  its  de- 
velopment, since  all  the  solid  ingredients  of  plants  are  assimilated  from  the 
sap,  which  is  rendered  liquid  by  water.     Plants,  however,  absorb  through 
their  roots  much  more  water  than  is  applied  to  the  enlargement  of  their 
structure,  and  in  such  cases  a  constant  evaporation  takes  place  from  their 


799.  The  carbon  existing  in  plants  is  entirely  derived  from  carbonic  acid, 
carbon  itself  being  insoluble  in  water.  Plants  absorb  carbonic  acid  principally 
from  the  air  through  their  leaves.  Although  but  2  measures  of  this  gas  are 
contained  in  5,000  of  air,  its  aggregate  supply,  by  reason  of  the  great  extent 
of  the  atmosphere,  is  very  large,  and  has  been  estimated  to  exceed  seven 
tons  for  each  acre  of  the  earth's  surface.  The  immensely-extended  surface 
presented  by  the  leaves  of  plants  enables  them  to  withdraw  carbonic  acid 
from  the  atmosphere  in  a  very  rapid  manner. 


•  In  the  leaf  these  pores  are  found  mainly  upon  the  under  side.  In  the  white  lily,  where 
they  are  unusually  large,  and  are  easily  seen  by  a  simple  microscope  of  moderate  power, 
there  are  about  60,000  to  the  square  inch  on  the  epidermis  of  the  lower  surface  of  the 
leaf,  and  only  about  3,000  in  the  same  space  upon  the  upper  surface.  More  commonly, 
there  are  few  or  none  upon  the  upper  side,  direct  sunshine  being  unfavorable  to  their 
operation.  Their  immense  numbers  make  up  for  their  minuteness.  They  are  said  to 
vary  from  less  than  1,000  to  170,000  to  the  square  inch  of  surface.— GRAY. 

QUESTIONS.— Do  they  exist  in  the  tissues  in  the  same  form  as  in  the  ashes  of  plants? 
Through  what  organs  do  plants  obtain  their  nutriment?  In  what  conditions  is  nutriment 
only  absorbed  by  plants  ?  From  what  source  do  plants  derive  oxygen  and  hydrogen  ? 
What  is  said  of  the  existence  of  water  in  plants? 


NUTRITION    AND    GROWTH    OF    PLANTS.      477 

Carbonic  acid  is  also  supplied  to  plants  from  the  soil  through  their  roots. 
Humus,  in  the  course  of  its  decomposition,  continually  evolves  carbonic  acid ; 
and  the  air  in  all  soils  rich  in  decaying  vegetable  matter  always  contains  a 
much  larger  proportion  of  carbonic  acid  than  an  equal  bulk  of  the  general 
atmosphere.  Carbonic  acid  does  not,  however,  enter  into  and  circulate  in 
the  structure  of  plants  as  a  gas,  but  always  in  a  state  of  solution.  In  the 
leaf  the  moisture  with  which  the  tissues  are  saturated  becomes  the  medium 
of  its  absorption ;  in  the  case  of  the  root,  it  is  taken  up  naturally  in  solution 
in  water.  Some  chemists  maintain  that  the  soluble  forms  of  humus  (crenic 
and  apocrenic  acids)  are  directly  absorbed  by  roots,  and  thus  become  sources 
of  nutriment  to  the  growing  plant.  This  theory,  from  the  fact  that  it  has 
been  strenuously  opposed  by  Liebig  and  other  authorities,  has  not  been  gen- 
erally received,  but  the  most  recent  investigations  appear  to  substantiate  its 
correctness. 

The  carbonic  acid  absorbed  by  the  plant,  either  by  its  leaves  or  roots,  is 
decomposed ;  its  carbon  constituent  being  retained  and  assimilated,  while  the 
oxygen  originally  combined  with  it  is  restored  to  the  atmosphere.  This  de- 
composition takes  place  mainly  in  the  leaves  of  plants,  and  is  effected  solely 
tinder  the  influence  of  light.  It  goes  on  most  actively  when  the  plant  is  ex- 
posed to  the  direct  action  of  the  rays  of  the  sun,  but  is  entirely  suspended 
during  the  night.  It  is  also  checked  in  a  very  marked  degree  during  the 
daytime,  when  the  light  of  the  sun  is  intercepted  by  thick  clouds. 

Plants,  therefore,  in  the  daytime  continually  absorb  carbonic  acid  and  exhale 
oxygen. 

In  the  night  this  process  is  to  a  degree  reversed  ;  carbonic  acid  is  absorbed 
as  before,  but  the  influence  of  light  being  withdrawn,  it  is  again  restored  to 
the  air  unchanged.  Oxygen,  also,  as  the  result  of  certain  processes  allied  to 
oxydation,  is  at  the  same  time  abstracted  to  a  very  small  extent  from  the  at- 
mosphere. The  action  of  oxygen  under  such  circumstances  is  illustrated  by 
the  fact  that  the  leaves  of  certain  plants  which  are  bitter  in  the  evening  are 
sour  in  the  morning,  inasmuch  as  the  products  formed  during  the  day  become 
acid  by  oxydation  at  night;  when,  however,  the  assimilation  of  carbon  is 
recommenced  under  the  influence  of  light,  the  excess  of  oxygen  is  neutral- 
ized, and  the  original  bitter  properties  are  restored.  Furthermore,  if  during 
the  night  a  plant  be  covered  by  a  bell-glass,  the  atmosphere  contained  in  it 
will  be  found  to  contain  a  larger  amount  of  carbonic  acid  than  before.  This 
is  occasioned  by  the  oxygen  of  the  air  surrounding  the  plant  effecting  an 
oxydation  on  its  surface,  and  thus  producing  a  certain  quantity  of  carbonic 
acid ;  the-  amount,  however,  is  very  unequal  in  different  plants,  and  is  most 
abundantly  produced  by  such  as  contain  a  large  proportion  of  easily  oxyd- 
izable  volatile  oil  in  their  glandular  vessels.  Flowers  and  fruits  also  form  an 

QUESTIONS.— What  is  the  source  of  carbon  to  plants  in  the  soil  ?  In  what  condition 
does  carbonic  acid  exist  in  plants  ?  What  becomes  of  the  carbonic  acid  absorbed  by 
plants?  Under  what  circumstances  does  its  decomposition  take  place  ?  State  the  action 
of  plants  by  day.  "What  takes  place  at  night  ?  How  may  the  decomposition  of  carbonic 
acid  be  illustrated  ? 


478  ORGANIC    CHEMISTRY. 

exception  to  the  usual  action  of  vegetation,  as  they  absorb  oxygen  from  the 
atmosphere,  and  evolve  carbonic  acid.* 

The  decomposition  of  carbonic  acid  by  the  green  portions  of  plants  may 
be  easily  demonstrated  by  placing  fresh  leaves  hi  a  bell  glass  partially  filled 
with  water,  and  partially  with  carbonic  acid  gas ;  on  exposing  the  glass  to 
the  sunshine,  the  carbonic  acid  disappears,  and  after  some  time  is  replaced 
by  a  rather  smaller  quantity  of  oxygen,  which  may  be  tested  hi  the  usual  man- 
ner. 

The  carbonic  acid  withdrawn  from  the  ah*  by  the  action  of  vegetation  is 
constantly  reproduced  and  restored  to  the  atmosphere  by  the  respiration  of 
animals,  and  by  the  processes  of  decay  and  combustion ;  and  these  two  classes 
of  phenomena  so  completely  compensate  and  balance  each  other,  that  the 
proportional  quantity  of  oxygen  and  carbonic  acid  present  in  the  atmosphere 
remains  ever  essentially  unchanged.  (§  330.) 

800.  It  is  the  generally  received  opinion  that  plants  derive  their  nitrogen 
entirely  from  the  soil,  by  means  of  their  roots,  in  the  form  of  ammonia,  al- 
though certain  eminent  French  chemists  maintain  that  this  element  is  in  part 
supplied  directly  from  the  atmosphere.     The  sources  of  supply  of  ammonia 
to  soils  are  numerous ;  it  is  absorbed  and  condensed  from  the  atmosphere  by 
dew,  rain,  and  snow,  and  also  by  the  clay  and  humus  of  the  Boil  itself.     It 
is  an  abundant  product  of  the  decomposition  of  all  nitrogenized  animal  and 
vegetable  substances,  and  is  undoubtedly  produced  to  some  extent  by  the 
direct  contact  of  humus  with  the  nitrogen  of  the  air. 

In  what  manner  the  assimilation  of  ammonia  takes  place  in  the  vegetable 
kingdom  is  not  certainly  known.  Its  decomposition,  however,  furnishes 
plants  with  an  additional  source  of  hydrogen.  The  quantity  of  nitrogen  con- 
tained in  plants  is  comparatively  small,  and  it  is  found  chiefly  in  the  sap  and 
in  the  seeda  In  2,500  Ibs.  of  hay  there  are  984  Ibs.  of  carbon  and  only  32 
Ibs.  of  nitrogen. 

801.  Plants  derive  their  mineral,  or  earthy  constituents  from  the  soil,  and 
the  solution  of  these  substances  in  water,  which  is  necessary  for  their  absorp- 
tion by  root-fibers,  is  greatly  facilitated  by  the  action  of  carbonic  acid. 
(§  432). 

802.  Soils  owe  their  origin  to  the  disintegration  or  gradual  crumbling 
down  of  rocks,  by  the  action  of  water,  air,  frost,  and  various  other  agencies. 
Through  the  action  also  of  air,  moisture,  and  carbonic  acid,  the  stony  parti- 

*  There  is  a  common  belief  that  plants  in  flower  at  night  deteriorate  the  air,  and  that, 
therefore,  their  presence  in  sleeping  apartments  is  objectionable.  The  ill  effects  noticed, 
if  actually  occurring,  are  probably  due,  not  to  the  formation  of  carbonic  acid,  but  to  the 
volatilization  of  certain  volatile  oils,  many  of  which,  in  even  very  small  quantities,  act 
powerfully  upon  the  animal  system. 

QUESTIONS. — How  is  the  carbonic  acid  withdrawn  from  the  air  by  plants  restored  ? 
From  what  source  do  plants  obtain  their  nitrogen  ?  Do  plants  absorb  nitrogen  directly 
from  the  atmosphere  ?  From  what  source  do  plants  derive  their  mineral  constituents  ? 
What  is  the  origin  of  soils  ?  Through  what  agency  are  certain  of  the  mineral  constituents 
of  a  soil  rendered  soluble  ? 


NUTRITION     AND    GROWTH     OF    PLANTS.       479 

cles  which  make  up  a  soil  are  chemically  decomposed,  and  certain  of  their  min- 
eral constituents,  potash,  soda,  etc.,  are  rendered  soluble  and  capable  of  assimi- 
lation by  plants.  The  most  abundant  constituent  of  soils  is  silica  (sand), 
which  frequently  forms  nine  tenths  of  their  entire  weight.  Good  arable  land, 
however,  always  contains  a  large  proportion  of  alumina  (clay),  and  in  soils 
underlayed  by  limestone  or  calcareous  rocks,  the  proportion,  of  carbonate  of 
lime  present  is  often  very  considerable. 

The  relative  proportions  of  sand,  clay,  and  lime  in  soils  give  to  them  cer- 
tain peculiar  physical  characters.  A  soil  in  which  sand  predominates  is  light 
and  porous ;  an  excess  of  clay,  on  the  other  hand,  renders  it  heavy  and  re- 
tentive of  moisture.  The  best  soils  are  those  in  which  the  earthy  constitu- 
ents are  so  proportioned  that  the  light,  porous  qualities  of  one  are  balanced 
by  the  close,  retentive  properties  of  the  other. 

The  quantity  of  organic  matter  (humus)  derived  from  the  decomposition  of 
animal  or  vegetable  substances  present  in  a  soil,  essentially  modifies  its  char- 
acter. The  average  amount  of  organic  matter  contained  in  soils  is  about  5 
per  cent.  Fertile  alluvial  soils,  or  those  deposited  from  water,  are  generally 
characterized  by  the  presence  of  a  much  larger  proportion,  and  in  some  peaty 
soils,  the  amount  may  exceed  70  or  80  per  cent. 

803.  Although  plants  obtain  a  large  proportion  of  their  nutriment  from 
the  air,  yet  as  they  abstract  from  the  soil  considerable  quantities  of  earthy 
matter,  which  is  only  replaced  naturally  by  the  slow  disintegration  of  min- 
eral substances,  it  is  evident  that  the  long-continued  cultivation  of  the  same 
plant  upon  the  same  soil  may  so  far  exhaust  its  soluble  mineral  constituents 
as  to  render  it  unfruitful.  This  is  especially  the  case  where  large  crops  are 
raised  year  after  year,  and  entirely  removed  from  the  soil  to  furnish  food  for 
men  and  animals.  As  different  plants,  however,  require  for  their  nourishment 
different  mineral  substances,  or  different  quantities  of  the  same  substance,  a 
soil  which  has  become  unfitted  for  the  growth  of  one  plant,  may  still  contain 
the  elements  necessary  for  the  support  of  another ;  and  hence  a  succession  of 
crops  of  different  vegetables  may  be  raised  upon  the  same  soil,  when  two 
successive  crops  of  the  same  vegetable  could  scarcely  be  obtained.  This  sys- 
tem of  cultivating  different  plants  in  succession,  upon  the  same  soil,  is  termed 
the  rotation  of  crops,  and  the  period  of  time  over  which  the  rotation  is  al- 
lowed to  extend  is  usually  several  years.  During  the  interval  which,  under 
these  circumstances,  elapses  between  two  successive  crops  of  the  same  na- 
ture, the  soil  has  time  to  renew  itself;  or  in  other  words,  it  regains  through 
the  gradual  decomposition  of  its  insoluble,  stony  compounds,  the  constituents 
originally  abstracted  from  it.  In  England,  wheat  is  ordinarily  grown  upon 
the  same  soil  only  once  in  four  or  five  years,  the  intermediate  crops  being 


QUESTIONS.— What  is  the  most  abundant  constituent  of  soils?  What  influence  has  an 
excess  of  sand  upon  a  soil  ?  What  clay  ?  What  is  the  composition  of  the  best  soils  ? 
What  is  the  average  quantity  of  organic  matter  in  soils?  How  does  the  growth  of  plants 
tend  to  impoverish  a  soil  ?  What  is  understood  by  the  rotation  of  crops  f  How  does  the 
system  of  rotation  tend  to  benefit  a  soil? 


480  OBGANIC     CHEMISTRY. 

turnips,  barley,  oats,  and  potatoes,  crops  which  require  but  a  small  quantity 
of  the  mineral  constituents  which  are  essential  to  the  growth  of  wheat. 

The  resuscitation  of  an  exhausted  soil  is  also  often  effected  by  allowing  it 
to  fallow,  or  remain  without  a  crop,  exposing  it  at  the  same  time  (by  plow- 
ing) to  the  action  of  air  and  moisture. 

804.  Manures , — The  method,  however,  of  obtaining  from  the  soil  the 
largest  produce,  consists  in  presenting  to  the  plants  cultivated  upon  it  all  the 
materials  requisite  for  their  nutrition  in  sufficient  quantity,  and  in  the  condi- 
tion which  will  most  readily  admit  of  their  absorption.  This  is  accomplished 
through  the  agency  of  manures. 

The  most  valuable  and  energetic  of  all  manures  are  the  excrements  of 
men  and  animals,  inasmuch  as  they  are  capable  of  yielding  to  the  soil,  through 
their  decomposition,  a  large  quantity  of  ammonia  and  carbonic  acid,  and  the 
principal  mineral  substances  which  enter  into  the  composition  of  plants.  By 
acting  as  ferments,  they  also  assist  in  rendering  useful,  materials  which  with- 
out them  would  be  far  less  beneficial.  The  flesh  and  blood  of  dead  animals, 
fat  and  oily  matters,  hair,  wool,  skin,  horns,  hoofs,  and  bones,  are  also  highly 
efficacious  as  manures.  Gwno,  which  is  the  decomposing  excrement  of  sea- 
birds,  owes  its  value  principally  to  the  ammonia  and  phosphate  of  lime  which 
it  is  capable  of  yielding  to  plants.  These  two  ingredients,  hi  the  best  varieties 
of  guano,  constitute  about  one  third  of  its  entire  weight.  Animal  substances 
which  decompose  most  readily,  such  as  excrement,  blood,  flesh,  etc.,  yield  am- 
monia and  carbonic  acid  most  rapidly,  and  constitute  the  most  powerful 
manures;  those,  on  the  contrary,  which  decompose  more  slowly,  are  less 
powerful,  but  more  lasting  in  their  effects. 

Animal  manures  exposed  to  air  are  liable  to  deterioration  by  the  volatiliza- 
tion and  escape  of  their  ammonia.  They  may  also,  when  incorporated  with 
the  soil,  prove  injurious  by  evolving  a  greater  quantity  of  ammonia  and  car- 
,  bonic  acid  than  plants  require  or  can  absorb.  Agriculturalists  express  this 
when  they  speak  of  a  manure  as  being  too  strong.  These  evils  may  be  in  a 
great  measure  prevented  by  incorporating  with  the  strong  manure  a  consid- 
erable quantity*  of  vegetable  refuse,  straw,  weeds,  leaves,  peat,  etc.,  which 
substances,  being  less  prone  to  decomposition,  check  the  otherwise  too  rapid 
putrefaction.  The  animal  products  at  the  same  time  react  upon  the  vege- 
table substances,  and  gradually  bring  them  into  such  a  state  as  renders  them 
also  most  valuable  additions  to  the  soil.  Common  farm-yard  manure  is  an 
example  of  a  mixture  of  this  character.  The  loss  of  ammonia  may  also  be 
effectually  prevented  by  adding  to  manures  a  small  quantity  of  a  weak  solu- 
tion of  any  acid,  or  gypsum  (sulphate  of  lime),  or  copperas  (sulphate  of  iron). 


QUESTIONS. — What  is  fallowing?  In  what  manner  can  the  largest  produce  be  obtained 
from  the  soil?  What  are  the  most  valuable  of  manures?  Why  are  animal  manures  es- 
pecially valuable  ?  What  is  guano  ?  To  what  does  it  mainly  owe  its  value  as  a  manure  ? 
"What  is  said  of  the  comparative  effect  of  different  animal  manures?  Under  what  circum- 
stances will  animal  manures  deteriorate  ?  When  are  they  said  to  be  too  "  strong  ?"  How 
may  these  evils  be  obviated  ? 


NUTRITION     AND     GROWTH     OF    PLANTS.      481 

805.  Vegetable  manures,  under  which  head  are  included  vegetable  refuse 
of  all  kinds,  straw,  leaves,  sea-weed,  and  green  crops  which  are  merely  sown, 
to  be  plowed  in,  yield  by  their  decomposition,  when  mixed  with  the  soil, 
carbonic  acid  and  small  quantities  of  ammonia  and  the  mineral  constituents 
of  plants.     They  also  render  a  soil  porous  and  retentive  of  moisture  and  am- 
monia.    They  are  most  advantageously  used  when  employed  in  combination 
with  some  kind  of  animal  manura 

806.  Mineral  manures  are  generally  used  for  specific  purposes.     Of  these 
the  most  important  is  lime.     This  substance  acts  mechanically  by  giving  a 
proper  consistency  to  soils,  and  chemically,  by  facilitating  the  decompositiou 
and  promoting  the  solubility  of  the  more  insoluble  mineral  and  vegetable  com- 
pounds.    Quicklime  is  especially  useful  in  soils  rich  in  humus — peaty  or  mossy 
soils.     Soils  of  this  kind  generally  contain  an  excess  of  acid,  which  greatly 
interferes  with  their  fertility ;  this  acid  is  neutralized  by  the  addition  of  lime. 
Quicklime,  however,  should  never  be  mixed  with  animal  manures,  as  it  tends 
to  promote  the  escape  of  ammonia.     Gypsum,  or  marl  which  contains  lime 
in  combination,  may  be  used  in  such  cases  with  beneficial  results.     Wood 
ashes  act  upon  soils  and  manures  in  the  same  manner  as  lime ,  they  are, 
however,  more  valuable  than  lime,  as  they  contain  alkaline  salts  and  phos- 
phoric acid.     Hard  coal  ashes  have  but  little  value  as  manures ;  they  do  not 
contain  any  appreciable  quantity  of  alkaline  salts  or  phosphoric  acid,  and 
consist  mainly  of  silica,  alumina,  oxyd  of  iron,  and  a  small  percentage  of 
sulphate  of  lime.     Phosphate  of  lime  is  an  exceedingly  valuable  manure,  and 
as  it  is  found  in  almost  ah1  plants,  it  may  be  applied  with  advantage  to  almost 
all  cultivated  soils.     It  exists  abundantly  in  bones  and  in  guano,  and  in 
smaller  quantity  in  all  organic  manures  and  in  the  ashes  of  plants.     Phos- 
phate of  lime  is  the  special  mineral  constituent  of  wheat,  and  its  presence  in  a 
soluble  condition  in  a  soil,  is  necessary  for  the  successful  cultivation  of  this 
cereal.      Gypsum  or  sulphate  of  lime  is  a  valuable  addition  to  soils  which  do 
not  contain  it.     It  is  partially  useful  as  supplying  lime  and  sulphuric  acid, 
and  partially  as  an  agent  for  fixing  ammonia.     It  is  especially  adapted  for 
clover,  bean,  and  pea  crops. 

A  thorough  tillage,  or  a  complete  pulverization  and  separation  of  the  par- 
ticles of  a  soil,  will  go  far  toward  compensating  for  a  lack  of  manures.  With 
every  increase  in  the  comminution  of  the  particles  of  a  soil,  an  increased 
power  is  given  to  the  soil  for  the  absorption,  retention,  and  condensation  of 
moisture,  ammonia,  and  carbonic  acid,  an  opportunity  for  the  free  permeation 
of  atmospheric  air,  a  facility  to  the  rootlets  of  plants  for  extension,  and  a 
consequent  increased  facility  for  receiving  and  appropnating  nourishment. 
This  fact  is  strikingly  illustrated  by  a  comparison  of  the  sterile  soils  of  New 

QUESTIONS. — What  is  the  action  of  vegetable  manures  ?  How  may  they  be  most  advan- 
tageously used  ?  What  is  said  of  lime  as  a  manure  ?  Upon  -what  soils  is  the  use  of  lime 
especially  beneficial?  When  should  lime  not  be  used?  What  is  said  of  the  fertilizing 
action  of  wood  ashes  ?  What  of  hard  coal  ashes  ?  What  of  phosphate  of  lime  ?  What 
of  gypsum  ?  What  is  said  of  the  importance  of  thorough  tillage  and  pulverization  of  a 
soil  ?  How  is  this  illustrated  ? 

21 


482  ORGANIC    CHEMISTRY. 

England  and  the  fertile  ones  of  the  West.  Both  have  been  formed  from  the 
disintegration  of  the  same  varieties  of  rocks,  and  both  contain  the  same  min- 
eral constituents  in  nearly  the  same  proportion.  In  the  former,  however,  the 
mineral  panicles  are  extremely  coarse,  but  in  the  latter  they  are  nearly  in  the 
state  of  an  impalpable  powder.  The  fertile  soils  of  the  "West  also  contain  a 
large  percentage  of  humus  in  an  advanced  stage  of  decomposition,  while  very 
often  the  humus  in  the  soils  of  New  England  is  in  a  state  allied  to  charcoal, 
and  completely  insoluble. 


CHAPTER    XXV, 

ANIMAL     ORGANIZATION     AND     PRODUCTS. 

807.  Animal    Organization  ,— Inasmuch  as  all  animals  derive  their 
sustenance,  either  directly  or  indirectly,  from  the  vegetable  kingdom,  the  ele- 
ments which  enter  into  their  composition  are  essentially  the  same  as  those 
contained  in  plants.     Most  animal  substances  are,  however,  more  complex 
in  their  nature  than  substances  of  vegetable  origin,    and   as  a  necessary 
consequence,  they  are  less  permanent,  and  the  products  of  their  decomposition 
are  more  numerous.     Water  and  fat  are  almost  the  only  substances  which 
contain  but  two  or  three  elements  that  exist  in  the  animal  organism — almost 
all  the  others  being  also  rich  in  nitrogen,  sulphur,  and  phosphorus. 

808.  Proximate  Animal    Constituents  . — The  chief  proximate 
constituents  that  are  found  in  the  animal  system  are  albumen,  fibriue,  caseine, 
gelatine,  fat,  water,  and  phosphate  of  lime.     The  proportions  of  solids  and 
fluids  in  the  animal  body  are  very  unequal.     A  man  of  lf)4  Ibs.  weight  con- 
tains 116  Ibs.  of  water,  and  only  38  Ibs.  of  dry  matter.     By  slow  desiccation 
this  water  may  be  got  rid  of,  when  the  body  will  assume  the  condition  pre- 
sented by  the  mummies  of  Egypt  and  Peru.     The  fluids  of  the  body,  as  they 
exist  in  the  living  tissues,  are  not  simply  water,  but  watery  solutions  of  va- 
rious organic  and  inorganic  substances. 

Of  the  proximate  animal  constituents  named  above,  albumen,  fibrine,  and 
caseine  appear  to  have  essentially  the  same  composition  and  properties  as 
the  substances  of  the  same  name  originating  in  vegetable  tissues.  The  two 
first  are  diffused  throughout  the  whole  body ;  the  third  is  found  only  as  a 
special  secretion. 

809.  Albumen . — The  best  example  of  animal  albumen  is  to  be  found 
in  the  white  of  an  egg.     This,  when  evaporated  to  dryness,  yields  about  one 

QUESTIONS. — What  are  the  elements  of  animal  substances  ?  In  what  respects  do  animal 
substances  differ  from  vegetable  ?  What  are  the  chief  proximate  constituents  of  the  ani- 
mal system  What  is  the  relation  between  the  solids  and  the  fluids  in  the  animal  body  ? 
What  is  said  of  the  composition  and  distribution  of  animal  albumen,  fibrine,  and  caseine  ? 
What  is  the  best  example  of  animal  albumen  ? 


ANIMAL  ORGANIZATION  AND  PRODUCTS.   483 

eighth  of  solid  albumen,  the  rest  being  water.  The  ashes  of  albumen  thus 
obtained  contain  common  salt,  carbonate,  phosphate  and  sulphate  of  soda,  and 
phosphate  of  lime,  which  saline  substances  constitute  about  5  per  cent,  of  the 
weight  of  the  white  of  the  egg,  or  1-J-  per  cent,  of  the  weight  of  the  dried  albu- 
men. The  yolk  of  eggs  consist  essentially  of  albumen,  holding  in  suspension 
drops  of  yellow  oil.  This  oil  forms  about  two  thirds  of  the  weight  of  the 
yolk  in  a  dried  state,  and  may  be  extracted  from  the  coagulated  yolk  by 
pressure,  or  by  digestion  in  alcohol. 

When  albumen  is  agitated  with  water,  little  solid  bodies  are  formed,  which 
under  the  microscope  resemble  the  cells  which  make  up  the  cellular  tissue  of 
animals,  and  are  perhaps  the  nearest  approach  to  an  organic  structure  that 
man  has  yet  been  able  to  produce  artificially. 

810.  Fibrineis  found  in  the  animal  body  in  two  distinct  states,  viz.,  in 
a  solid  condition  in  muscular  flesh,  and  as  a  fluid  in  the  blood.  A  piece  of 
lean  beef  washed  in  cold  water  until  it  is  perfectly  white,  affords  us  an  ex- 
ample of  fibrine  hi  the  first  condition,  associated  with  membraneous  matter, 
nerves,  fat,  etc.  It  may  be  extracted  from  the  blood  in  a  purer  condition, 
by  strongly  agitating  that  fluid,  in  its  recent  and  warm  state,  with  a  bundle 
of  twigs.  The  fibrine  adheres  to  these  latter  in  the  form  of  long,  elastic 
strings,  and  is  removed  and  cleansed  by  washing  with  cold  water.  In  this 
condition  it  contains  only  a  little  fat,  pIG>  237. 

which  may  be  extracted  by  ether. 

The  lean  part  of  the  muscles  of  all 
animals  consists  chiefly  of  fibrine,  and 
it  is,  therefore,  the  principal  constituent 
of  animal  flesh.  Fig.  235  represents 
the  structure  of  muscle  as  seen  under 
the  microscope,  the  cross  wrinkles 
showing  the  way  in  which  the  fibers  contract  in  the  living  animal.  Fibrine 
derives  its  name  from  its  peculiar  fibrous  appearance,  but  under  the  micro- 
scope it  appears  to  be  composed  of  small  globules  arranged  in  strings.  When 
pure,  it  is  quite  tasteless,  and  insoluble  both  in  hot  and  cold  water,  but  by 
long-continued  boiling  it  is  partially  dissolved.  By  drying  it  shrinks  pro 
digiously  in  volume,  loses  about  80  per  cent,  of  water,  and  becomes  transpa- 
rent and  horny,  and  in  this  condition  may  be  preserved  for  an  indefinite  pe- 
riod. Fibrine,  when  hi  solution,  assumes  the  solid  form  spontaneously,  as 
as  soon  as  it  is  withdrawn  from  the  influence  of  life.  It  is  this  which 
causes  blood  to  coagulate  almost  as  soon  as  it  is  drawn  from  the  veins — the 
coagulation  being  a  net-work  of  fine  fibers  of  fibrine  inclosing  the  liquid  se- 


QuESTio-srs.— Of  what  does  the  white  of  an  egg  consist  ?  What  is  the  composition  of  the 
yolk  ?  What  phenomenon  of  albumen  is  mentioned  ?  In  what  conditions  is  fibrine  found 
in  the  animal  economy  ?  How  may  it  be  prepared  in  a  state  approaching  to  purity?  Of 
what  part  of  the  animal  system  does  it  form  the  principal  part  ?  What  is  the  origin  of  its 
name  ?  What  are  its  properties  ?  What  is  said  of  fibrine  in  solution  ?  What  causes  the 
coagulation  of  the  blood  ? 


484  ORGANIC    CHEMISTRY. 

rum  and  coloring  principle  of  the  blood.  Owing  to  this  circumstance,  little 
or  nothing  is  known  of  fibrine  in  the  soluble  state,  but  it  is  believed  that  the 
chemical  composition  of  soluble  and  insoluble  fibrine  is  somewhat  different. 
Its  composition  is  represented  by  the  formula  C^HsioNsoOmPS. 

811.  C  a  s  e  i  n  e  in  the  animal  system  occurs  only  in  milk.    Its  composi- 
tion and  properties  have  been  already  described.     (§  706.) 

812.  Gelatine  .—Various  parts  of  the  animal  body,  particularly  the  skin, 
the  tendons,  cartilage,  and  the  soft  portions  of  the  bones,  dissolve  completely 
by  long  boiling  in  water,  and  produce  a  liquid  which  solidifies  on  cooling  to  a 
jelly.     The  substance  so  produced  is  termed  gelatine.     Chemists  do  not  regard 
it  as  existing  naturally  in  the  system,  inasmuch  as  it  is  never  found  in  the 
fluids  of  the  body,  as  might  be  expected  from  its  ready  solubility  in  warm 
water ;  but  it  is  supposed  to  be  produced  by  a  specific  chemical  change  of 
some  of  the  albuminous  principles  by  the  action  of  the  hot  water  and  the 
oxygen  derived  from  the  air.     The  gelatine  extracted  from  cartilage  appears 
to  differ   somewhat   from   that  extracted  from  animal  membranes  proper, 
and  has  received  the  distinctive  name  of  chondrine.     The  term  cartilage  is  ap- 
plied to  a  dry,  elastic  tissue,  very  widely  distributed  in  the  animal  economy, 
"which  sometimes  serves  to  connect  the  ends  of  bones  which  move  upon  each 
other,  and  sometimes  constitutes  prolongations  of  the  bones  themselves,  as  for 
example,  in  the  ribs,  thus  increasing  their  elasticity. 

Gelatine  is  an  important  constituent  of  the  animal  body,  and  is  obtained  from 
almost  all  solid  parts  of  it,  but  more  especially  from  the  tendons,  ligaments, 
the  inner  skin,  and  from  bones  and  horns.  It  is  very  rich  in  nitrogen,  and 
contains  some  sulphur,  but  it  is  not  allied  to  the  proteine  group  of  substances. 
Its  formula  is  CisIIioN^OsS.  Gelatine  is  exclusively  an  animal  product,  and 
is  never  found  in  plants,  pectiue  being  the  vegetable  jelly  principle. 

Common  glue  is  dried  gelatine,  and  is  prepared  by  boiling  refuse  skin  and 
bones,  and  evaporating  the  solution.  The  liquor  yields  on  cooling  a  thick 
jelly,  which  is  cut  by  wires  into  thin  layers,  and  dried  by  exposure  to  the 
air.  Isinglass,  which  is  the  purest  variety  of  gelatine,  is  the  dried  swimming, 
or  air-bladder  of  several  varieties  of  fish,  especially  of  the  sturgeon.  Gelatine 
is  also  extracted  from  the  tender  and  ligamentous  part  of  calves'  feet,  for  tho 
purpose  of  forming  the  well  known  "calves'  foot  jelly." 

A  dilute  solution  of  gelatine  prepared  from  clippings  of  hides  constitutes 
the  size  which  is  usually  applied  to  paper  to  fill  up  its  pores,  and  thus  pre- 
vent the  spreading  of  ink.  The  difference  between  writing  and  printing  paper 
consists  simply  in  the  fact,  that  the  former  is  sized,  while  the  latter  is  not* 

*  A  cheaper  kind  of  sizing  for  paper  is  also  prepared  by  boiling  resin  with  a  strong  so- 
lution of  potash.  This  is  first  added  to  the  paper  pulp,  and  when  it  has  become  thor- 
oughly incorporated,  a  solution  of  alum  is  poured  in.  The  alumina  displaces  the  potash 
in  combination  with  the  resin,  and  forms  a  more  insoluble  compound  in  the  fibers  of  tho 
paper- 

QUESTIONS — What  is  said  of  caseine?  How  is  gelatine  prepared  ?  What  is  gelatine? 
What  is  said  of  the  distribution  and  composition  of  chondrine  ?  What  is  cartilage  ?  What 
is  glue?  What  is  isinglass  ?  What  is  size?  For  what  purpose  is  size  applied  to  paper  ? 


ANIMAL    ORGANIZATION    AND    PRODUCTS.      485 

Gelatine  is  largely  employed  as  an  article  of  food,  in  soups,  jellies,  etc.,  but 
it  possesses  very  little  nutritive  value.  In  an  indirect  way,  under  the  condi- 
tions of  a  restricted  diet  usually  met  with  in  a  sick  room,  its  administration 
in  the  form  of  jellies,  etc.,  appears  to  be  beneficial,  as  it  seems  to  protect  some 
of  the  constituents  of  the  body  from  waste. 

Gelatine  united  with  tannic  and  gallic  acids  produces  insoluble  com- 
pounds, and  tho  application  of  this  principle  to  the  manufacture  of  leather 
has  been  already  noticed.  Skins  may,  however,  be  converted  into  leather  by 
other  methods;  as  by  impregnating  them,  after  they  have  been  freed  from 
fatty  matters  by  digestion  in  alkalies,  with  a  solution  of  common  salt  and 
alum,  and  then  working  them  with  various  oils.  Glove  leather  is  prepared 
iti  this  manner  ;  the  still  softer  chamois,  or  wash-leather  is  obtained  by  work- 
ing the  skins  for  a  long  time  with  the  brains  of  certain  animals  or  the  yolks 
of  eggs — the  effect  in  both  instances  being  due  to  the  action  of  certain  pecu- 
liar oily  or  fatty  substances. 

813.  G  1  y  c  o  c  o  1 1 , — By  boiling  gelatine  with  dilute  sulphuric  acid,  and 
afterward  separating  the  acid  by  chalk,  a  very  remarkable  change  is  effected — 
the  gelatine  being  converted  into  a  sweet,  crystallizable  substance,  which  is 
termed  glycocoll,  or  sugar  of  gelatine. 

814.  Brain    and    Nerves  ,— The  substance  of  the  brain,  nerves,  and 
spinal  marrow  differs  from  that  of  all  the  other  animal  textures.     It  appears 
to  be  albumen  in  a  peculiar  state,  associated  with  certain  remarkable  fatty 
substances,  and  in  the  brain  especially  a  large  amount  of  unoxydized  phos- 
phorus is  believed  to  bo  present.     Only  about  one  fifth  part  of  the  nervous 
tissue,  however,  is  solid  matter.     The  phosphorus  contained  in  the  brain  ia 
said  to  amount  to  3  or  4  per  cent,  of  its  entire  weight. 

815.  The    Skin  of  animals  consists  of  two  layers,  the  skin  proper,  called 
also  the  cutis,  and  the  derma,  which  envelopes  the  muscles  and  the  bones ; 
and  the  outer  layer,  the  epidermis,  or  cutick,  which  originates  from  the  for- 
mer, and  consists  mainly  of  albuminous  cells,  which  losing  their  liquid  con- 
tents by  evaporation,  gradually  become  flattened  scales  at  the  surface.     These 
undergo  constant  exuviation,  and  are  constantly  replaced  from  beneath,  tho 
superficial  ones  becoming  dry  and  horny  (scarf  skin),  and  serving  as  a  pro- 
tection to  the  sensitive  or  true  skin  underneath.     The  lowest  portion  of 
the  cuticle,  resting  on  the  cutis,  is  called  the  rete  mucosum,  and  contains  the 
pigment  which  in  the  dark  races  imparts  color  to  the  skin.     This  pigment 
seems  to  be  produced  by  the  agency  of  sun-light  and  continued  high  tem- 
perature, and  contains  a  large  percentage  of  carbon. 

The  cuticle,  or  outer  skin  of  most  animals  is  perforated  by  numerous  small 
orifices,  through  some  of  which  hairs  pass,  while  others  give  passage  to  the 
fluids  of  perspiration,  or  allow  certain  oily  fluids  to  exude.  "  In  the  human 

QUESTIONS. — What  is  the  nutritive  value  of  gelatine  ?  How  is  leather  formed  other 
than  by  tanning?  What  is  glycocoll?  What  is  said  of  the  composition  of  the  brain  and 
nerves?  Of  what  does  the  skin  consist?  How  is  the  epidermis  formed?  What  is  the 
rete  mucosum  ?  What  is  said  of  the  pores  of  the  skin  ? 


486 


ORGANIC     CHEMISTRY. 


FiG.  236. 


system  the  pores  are  more  numerous  in  some  parts  of  the  body  than  in  others, 
but  the  outer  skin  of  a  full-grown  man  is  sprinkled  over  with  about  seven 
millions  of  them,  while  the  united  length  of  certain  spiral  vessels  connected 
with  them  is  reckoned  at  28  miles."  Through  the  pores  of  the  skin,  also, 

air  enters  and  escapes  continually  in 
a  healthy  state  of  the  body,  as  it  does 
from  the  air-vessels  of  the  lungs. 

Fig.  236  represents  a  vertical  sec- 
tion of  the  skin  greatly  magnified,  a 
being  the  cuticle,  or  outer  skin,  b  d 
the  true  skin,  e  the  sweat  glands  and 
their  ducts,  the  outlets  at  the  surface 
being  pores,  /  hairs,  g  cellular  tissue. 
816.  Horny  M  a  1 1  e  r .— Hair, 
wool,  bristles,  feathers,  nails,  claws, 
and  hoofs  of  animals  are  regarded  as 
having  the  same  general  chemical 
composition  as  that  of  the  epidermis, 
of  which  they  may  be  considered  as 
appendages.  They  are  insoluble  in 
water,  but  soften  in  boiling  water, 
and  entirely  dissolve  by  continued 
digestion  in  caustic  alkalies.  They 
contain  several  oily  or  fatty  sub- 
stances, generally  colored,  from  which 
they  derive  their  peculiar  hue. 

Each  hair  originates  in  a  little  flask-shaped  follicle  (/  Fig.  236),  which  is 
formed  by  a  depression  of  the  cutis,  and  lined  by  a  continuation  of  the  cuticle. 
The  hair  grows  by  constant  prolongation  from  this  follicle,  and  its  color  is 
due  to  a  peculiar  colored  oil,  which  in  black  hair  contains  a  considerable  quan- 
tity of  iron.  The  surface  of  the  hair  is  scaly,  and  not  smooth,  as  it  appears 
to  the  naked  eye ;  and  in  the  case  of  wool,  which  is  a  modification  of  hair, 
the  edges  of  the  fiber,  seen  under  a  microscope,  have  the  appearance  of  a 
fine  saw,  with  the  teeth  sloping  in  a  direction  from  the  roots  to  the  points. 
"Were  a  number  of  thimbles  with  uneven  edges  inserted  into  each  other,  a 
cylinder  would  result  not  dissimilar  in  outline  from  a  filament  of  merino 
wool,  the  appearance  of  which,  under  the  microscope,  is  represented  by  Fig. 
237.  This  peculiar  structure  of  wool  gives  it  the  property  of  felting,  so  that 
when  a  mass  of  wool  is  alternately  compressed  and  relaxed,  the  little  imbri- 
cations or  scales  of  the  fibers  lay  hold  of  and  match  into  each  other,  and  thus 
compact  the  whole  into  a  solid  tissue,  or  felt.  Some  varieties  of  hair,  included 
under  the  term  fur,  have  also  sufficiently  roughened  surfaces  to  enable  them 

QUESTIONS. — What  is  said  of  the  composition  of  hair,  horns,  etc.  ?  What  of  the  origin 
of  hair  ?  To  what  does  hair  owe  its  color  ?  What  is  the  external  structure  of  hair  ? 
Why  does  wool  felt? 


ANIMAL     ORGANIZATION     AND    PRODUCTS.      487 


to  felt.    Fig.  238  exhibits  the  appearance  of  the  hair  of  the  seal  (a)  and  of  a 
species  of  caterpiller  (6),  pIG.  238. 

when  viewed  under  the 


PiG.  237. 


microscope. 

817.  Bones.— The 
bones  of  animals  are 
composed  of  organic 
matter,  which  is  essen- 
tially the  same  as  car- 
tilage, and  of  earthy 
matter,  consisting  chief- 
ly of  phosphate  and 
carbonate  of  lime — the 
latter  constituting  in 
mammalia  about  two 

thirds  of  the  weight  of  the  bone.*  The  organic 
and  earthy  bases  contained  in  bones  may  be  easily  separated  from  each  other. 
Thus  when  a  bone  is  digested  for  some  days  in  a  dilute  solution  of  hydro- 
chloric acid,  the  earthy  salts  dissolve  out,  leaving  the  cartilage  soft  and  flexi- 
ble, but  retaining  exactly  the  shape  of  the  bone.  To  accomplish  this  per- 
fectly, it  is  necessary  to  renew  the  liquor  several  times,  and  finally  to  wash 
the  cartilage  with  fresh  water  until  no  trace  of  acid  remains.  The  cartilage 
may  also  be  removed  by  heating  the  bone  for  some  time  in  an  open  fire  with 
free  access  of  air — the  organic  matter  in  this  way  being  burned  away,  while 
the  bone-earth  remains. 

The  bones  of  mammalia  and  of  birds  agree  very  closely  in  chemical  com- 
position, but  the  bones  of  fishes  vary  considerably  as  regards  the  relative  pro- 
portions of  contained  earthy  and  organic  matter.  In  what  are  called  the 
cartilaginous  fishes,  sharks,  etc.,  the  bones  are  almost  entirely  destitute  of 
calcareous  salts,  and  in  the  bones  of  all  fishes  the  proportion  of  cartilaginous 
matter  is  always  greater  than  in  those  of  other  vertebrated  animals ;  hence 
the  flexibility  of  the  bodies  of  fishes.  The  composition  of  fish-scales  resembles 
that  of  bone,  since  they  contain  from  40  to  50  per  cent,  of  phosphate  of  lime, 
from  3  to  10  per  cent,  of  carbonate  of  lime,  and  from  40  to  55  per  cent,  of 
organic  matter. 

*  The  following  is  an  average  composition  of  the  bones  of  a  healthy  adult  man : — 

Cartilage 32-17 

Blood  vessels 1  -13 

Phosphate  of  lime 51-04 

Carbonate  of  lime 11  '30 

Fluoride  of  calcium 2-00 

Phosphate  of  magnesia 1  "16 

Soda,  chloride  of  sodium 1-20 

160-00 


QUESTIONS. — What  is  the  composition  of  bones  ?    How  may  the  constituents  of  bones  be 
separated  ?    How  do  the  bones  of  mammalia,  birds,  and  flshes  correspond  ? 


488  ORGANIC     CHEMISTRY. 

818.  The   Teeth  have  essentially  the  same  composition  as  the  bones, 
except  that  they  contain  less  cartilage.     The  white  external  part  of  the  tooth 
beyond  the  gum,  called  the  enamel,  is  almost  wholly  composed  of  phosphate 
of  lime,  carbonate  of  lime,  and  a  small  quantity  of  fluoride  of  calcium,  and 
contains  only  a  trace  of  animal  matter, 

819.  Shells  are  composed  of  a  mixture  of  carbonate  and  phosphate  of 
lime.     The  shells  of  Crustacea,  lobsters,  crabs,  etc.,  usually  contain  from  50 
to  60  per  cent  of  carbonate  of  lime,  from  4  to  5  per  cent,  of  phosphate,  and 
the  balance  animal  matter.     The  shells  of  mollusca,  oysters,  clams,  etc,,  on 
the  contrary,  are  nearly  pure  carbonate  of  lime,  and  contain  scarcely  any 
phosphates  or  organic  matter. 

820.  M  i  1  k.  —  This  peculiar  liquid  is  secreted  by  the  female  of  the  class 
mammalia  for  the  support  of  its  young,  and  seems  to  contain  the  game  con- 
stituents, although  in  somewhat  different  proportions,  in  all  the  different 
species  of  animals  producing  it.     Milk  is  wonderfully  adapted  for  the  office 
it  is  naturally  intended  to  discharge,  vizu,  that  of  providing  materials  for  the 
rapid  growth  and  development  of  the  young  mammalian  animal  •  inasmuch 
as  it  contains  caaeine,  a  nitrogenous  matter  nearly  identical  in  composition 
with  muscular  flesh,  fat,  sugar,  and  various  salts,  the  most  important  constitu- 
ent of  the  latter  being  phosphate  of  lime.     This  last  is  held  in  complete  solu- 
tion in  the  slightly  alkaline  liquid,  and  sustains  an  important  relation  to  the 
formation  and  growth  of  bone.    The  following  analysis  exhibits  the  com- 
position of  1,000  parts  of  cow's  milk  in  a  fresh  state  : 

Water  .....................  .  ......................  873-00 

Caseine  ...........................................  48-20 

Fat  (butter)  .......................................  30-00 

Milk  sugar.  .......................................  43-90 

Phosphate  of  lime,  magnesia,  and  iron  ..............  2-80 

Chlorides  of  potassium  and  sodium,  with  a  little  free 

Boda  in  combination  with  caseine  ...............  2  '10 


"Woman's  milk  contains  more  sugar,  but  less  caseine  and  butter  than  the 
milk  of  the  cow.  The  latter  is  not  so  well  adapted  to  the  functional  wants 
of  the  child,  but  may  be  improved  by  diluting  it  with  water  and  sweetening 
it  with  sugar,  the  effect  of  which  is  to  reduce  the  percentage  of  the  nitrogen- 
ized  element,  the  caserne,  and  render  it  more  suitable  for  digestion  and  assimi- 
lation. "  Milk,  moreover,  is  not  suitable  as  the  sole  nourishment  of  adult 
life,  since  it  does  not  contain  in  sufficient  quantity  those  phosphorized  com- 
pounds which  are  necessary  to  repair  the  waste  of  the  tissues,  which  at  this 
period  are  more  active  than  in  infancy." 

When  milk  is  viewed  under  a  microscope  of  moderate  power,  it  is  seen  to 
consist  of  a  perfectly  transparent  liquid,  in  which  are  suspended  numerous 


QUESTIONS.— What  is  the  composition  of  the  teeth  ?  Of  shells  ?  "What  is  mflk?  What 
is  its  natural  office ?  What  is  its  general  composition?  In  what  respect  does  -woman's 
milk  differ  from  cow's  ?  What  is  the  appearance  of  milk  under  the  microscope  ? 


ANIMAL     ORGANIZATION    AND    PBOBUCTS,      489 


globules  of  fat,  as  is  represented  in  Fig,  FIG.  239. 

239.  These  globules  are  the  butter,  and 
mainly  give  to  milk  its  opaque,  white 
appearance.  When  milk  is  allowed  to 
stand,  the  globules,  by  virtue  of  their 
low  specific  gravity,  rise  to  the  surface, 
and  form  a  layer  of  cream,  and  by  strong 
agitation  or  churning,  they  may  be  fur- 
ther made  to  coalesce  into  a  mass,  and 
form  "butter."  It  is  also  believed  that 
each  fat  globule  is  inclosed  in  a  little  sack 
of  caseine,  which  is  ruptured  by  the  agita- 
tion. During  the  operation  of  churning, 
oxygen  is  absorbed  from  the  air,  the 
temperature  rises,  and  the  milk,  if  not  already  acid,  turns  sour. 

Butter  consists  of  a  mixture  of  margarine,  oleine,  and  a  peculiar  volatile, 
odoriferous  principle  termed  butyrine,  which  contains  butyric  acid.  In  order" 
that  butter  should  keep  well,  it  is  necessary  that  the  buttermilk  should  be 
thoroughly  freed  from  it,  since  the  caseine  and  albumen  contained  in  this 
readily  undergo  decomposition,  and  produce  an  acid  fermentation  which  sep- 
arates the  butyric  acid  and  other  volatile  acids,  and  imparts  to  the  butter  a 
disagreeable,  rancid  taste.  This  same  object,  L  e.,  the  preservation  of  butter, 
can  be  also  attained  by  melting  the  butter,  when  the  watery  part  subsides 
and  carries  with  it  the  azotized  matter.  The  flavor  of  the  butter  is,  however, 
somewhat  impaired  by  this  process. 

821.  Milk,  when  in  a  fresh  state,  is  always  feebly  alkaline ;  but  it  soon 
sours  in  the  air,  particularly  in  warm  weather— lactic  acid  being  developed. 
The  presence  of  this  acid  causes  the  caseine  to  coagulate,  or  become  inso- 
luble, when  it  separates  in  clots,  carrying  the  fatty  globules  with  it.     Milk  in 
this  condition  is  said  to  be  turned.     This  change  may  be  prevented,  without 
injuring  the  quality  of  the  milk,  by  the  addition  of  a  minute  quantity  of  car- 
bonate of  soda. 

822.  C  h  e  e  s  e  is  a  mixture,  in  various  proportions,  of  coagulated  cascino 
and  butter.     The  caseous  matter  ig  separated  in  the  form  of  cheese,  by  leav- 
ing the  milk  for  some  little  time  at  a  temperature  of  120°  F.  in  contact  with 
a  piece  of  the  lining  membrane  of  the  stomach  of  a  calf,  which  is  called  ren- 
net.    This  by  its  presence  is  believed  to  cause  a  sort  of  acid  fermentation, 
which  causes  the  milk  to  separate  into  a  solid  white  opaque  curd,  and  a  thin, 
translucent  whey,  the  former  consisting  chiefly  of  caseine  and  butter,  and  the 
latter  of  water,  holding  in  solution  most  of  the  saline  constituents  of  the 
milk,  together  with  the  milk  sugaf.     The  coagulum  thus  obtained  is  sepa- 

QTTESTIONB. — In  what  condition  does  butter  exist  in  milk  ?  How  is  buttef  collected  In 
a  separate  state?  What  is  its  composition?  Why  is  butter  containing  butter-milk  liable 
to  deteriorate?  How  does  the  melting  of  butter  tend  to  preserve  it?  What  ia  the  chem- 
ical condition  of  milk  ?  What  causes  it  to  coagulate  ?  What  is  cheese  ?  How  is  it  manu- 
factured? 


490 


ORGANIC     CHEMISTRY. 


rated  from  the  whey  by  straining ;  then  drained,  mixed  with  a  portion  of  salt, 
.  and  sometimes  other  condiments,  and  subjected  to  pressure.  The  product  is 
cheese,  which,  when  kept  for  several  months  in  a  cool  situation,  undergoes  a 
kind  of  putrefaction,  and  .obtains  thereby  a  peculiar  taste  and  odor.  The 
goodness  of  cheese  depends  upon  the  proportion  of  cream  left  in  the  milk, 
and  upon  the  method  of  its  manufacture. 

823.  B  1  o  o  d.— "  The  blood  is  the  general  circulating  fluid  of  the  animal 
body,  the  source  of  all  nutriment  and  growth,  and  the  general  material  from 
which  all  the  secretions,   however  much  they  may  differ  in  properties,  are 
derived.     It  also  serves  the  scarcely  less  important  office  of  removing  and 
carrying  off  from  the  body  principles  which  are  hurtful,  or  no  longer  re- 
quired." 

In  all  vertebrated  animals,  viz.,  man,  mammals,  birds,  reptiles,  and  fishes, 
the  blood  has  a  bright  red  color ;  while  in  the  invertebrata,  as  insects,  the 
Crustacea,  mollusca,  and  zoophytes,  it  is  very  often  colorless,  but  sometimes 
tinged  with  red,  yellow,  green,  or  other  hues.  » 

824.  Composition    of  the    Blood  .—The  blood,  as  seen  under  the 
microscope,  circulating  in  the  vessels,  appears  to  consist  of  a  colorless  liquid, 
holding  in  suspension  little  globules,   called  corpuscles,  or  cells.     Some  of 
these,  hi  man,  are  white,  but  most  are  red,  and  give  to  the  blood  its  color. 
The  red  corpuscules  vary  in  size  and  shape  in  different  animals,  and  the  mi- 
croscopist,  taking  advantage  of  this  circumstance,  is  enabled,  even  after  the 
lapse  of  years,  to  distinguish  in  the  dried  stain,  human  from  animal  blood, 
and  also  to  pronounce  with  certainty  whether  a  particular  spot  is  occasioned 

by  blood  or  some  other  liquid. 

In  man  they  appear  as  circular 

flattened  disc,  having  an  average 

diameter  of  l-3200th  of  an  inch, 

and  a  thickness  of  l-124,000th. 

In  reptiles  they  are  elliptical  and 

larger  than  in  man.      Fig.  240 

represents  their   appearance  in 

human     blood    magnified    500 

diameters,  and  Fig.  241  their  ap- 
pearance in  the  blood  of  a  frog, 

magnified  250  diameters.    When 
dried,  they  form,  in  man,  on  an  average,  about  13  per  cent,  of  the  whole 
weight  of  fresh  blood. 

In  man  and  all  warm-blooded  animals,  the  color  of  the  blood  in  the  arteries 
is  of  a  bright  scarlet,  while  in  the  veins  it  is  dark  red.  These  changes  of 
color  are  primarily  due  to  the  action  of  atmospheric  oxygen  upon  the  blood, 
while  passing  through  the  lungs, 


FIG.  240. 

^y 
&    ®^ 


/? 


QUESTIONS. — What  is  the  Wood  ?  What  is  said  of  its  color?  "What  is  its  appearance 
under  the  microscope  ?  What  is  said  of  the  blood  corpuscles  ?  What  is  Baid  of  the  color 
of  the  blood  in  the  veins  and  arteries  ? 


ANIMAL  ORGANIZATION  AND  PRODUCTS.   491 

The  fluid  of  the  corpuscles  contains  the  coloring  matter  of  the  blood,  which 
is  called  hoematine,  particles  of  fat,  a  colorless  substance  called  globuline,  which 
resembles  caseine  in  its  properties  and  composition,  and  various  saline  mat- 
ters. Hcematine  is  remarkable  for  containing,  as  an  essential  ingredient,  oxyd 
of  iron,  which  may  be  easily  extracted  and  tested  by  igniting  a  little  dried 
clot  of  blood  in  a  crucible,  and  digesting  the  residue  with  hydrochloric  acid  ; 
the  solution  thus  obtained,  gives  Prussian  blue,  with  ferrocyanide  of  potassium. 

The  colorless  corpuscles  of  the  blood  are  supposed  to  contain  principally 
fat. 

The  colorless  liquid  surrounding  the  blood  corpuscles  is  water,  holding  in 
suspension  or  solution  a  great  number  of  different  substances,  viz.,  albumen, 
fibrine,  fat,  and  a  great  number  of  salts,  such  as  the  phosphates  of  soda, 
lime,  and  magnesia,  the  carbonates  and  sulphates  of  potash  and  soda,  and 
the  chlorides  of  potassium  and  sodium.  It  also  contains  several  gases,  oxy- 
gen, carbonic  acid,  and  nitrogen,  arising  from  the  action  of  air  in  the  lungs. 
A  healthy,  full-grown,  average  sized  man,  contains  about  20  Ibs.  of  blood  ; 
1,000  parts  of  which  consist  of  700  to  790  parts  water,  60  to  TO  albumen,  2 
or  3  fibrine,  1*4  to  3  of  fat,  and  10  of  mineral  salts. 

The  heat  of  the  blood  depends  in  a  great  degree  upon  tho  activity  of  the 
process  of  respiration.  In  man,  when  in  a  state  of  health,  its  temperature  re- 
mains, under  almost  all  circumstances,  in  the  extreme  cold  of  the  polar  re- 
gions and  under  the  tropics,  at  about  98°  F.  In  birds,  the  temperature  is 
sometimes  as  high  as  108°  F.  In  fishes,  it  is  about  that  of  the  water  in 
which  they  live.  Animals  whose  temperature  is  but  little  higher  than  tho 
medium  in  which  they  live  are  called  cold-blooded,  while  those  whose  tem- 
perature is  warmer  than  the  air  which  surrounds  them,  are  called  warm- 
blooded. 

In  its  ordinary  state,  the  blood  has  a  decidedly  alkaline  reaction,  a  saline 
taste,  and  a  peculiar  odor.  When  taken  from  the  living  animal,  it  soon  un- 
dergoes spontaneous  coagulation,  and  separates  into  two  portions ;  one,  a 
pale,  yellowish,  slimy  fluid,  called  the  serum,  the  other  a  gelatinous,  red 
mass,  called  the  dot,  or  coagulum.  The  former  contains  nearly  all  the  albu- 
men and  saline  constituents  of  tho  blood,  while  the  latter,  as  before  stated, 
is  produced  by  the  coagulation  of  the  fibrine,  which,  "  although  constituting, 
when  dry,  a  very  small  proportion  of  the  whole,  yet  in  the  bulky  and  swol- 
len condition  in  which  it  .separates,  is  voluminous  enough  to  entangle  in  its 
net- work  of  fibers  the  whole  of  the  coloring  matter,  and  cause  its  mechanical 
separation."  The  cause  of  the  coagulation  is  not  fully  determined ;  the  ad- 
dition of  certain  saline  substances,  such  as  a  saturated  solution  of  chloride 
of  sodium,  cither  retards  or  prevents  it ;  while  alum,  and  the  oxyds  of  zinc  and 

QUESTIONS. — What  is  the  composition  of  the  blood  corpuscles  ?  What  of  tho  fluid  sur. 
rounding  the  corpuscles  ?  What  quantity  of  blood  is  contained  In  a  healthy  man  ?  What 
are  the  general  constituents  of  the  blood?  What  is  said  of  the  heat  of  the  blood?  What 
are  -warm  and  cold-blooded  animals  ?  What  change  does  the  blood  undergo  when  drawn 
from  the  veins  ?  What  is  the  serum  ?  What  tho  clot  ? 


492  ORGANIC     CHEMISTRY. 

copper,  promote  it.  The  blood  of  persons  also  who  have  died  a  sudden,  vio- 
lent death  by  some  kinds  of  poison,  or  from  mental  emotion,  is  usually  found 
in  a  fluid  state.* 

825.  Nutrition  . — The  constant  waste  of  the  animal  body  consequent 
on  the  discharge  of  the  various  functions  necessary  to  the  support  of  life,  re- 
quires that  an  equally  constant  supply  of  new  material  should  be  afforded, 
from  which  the  repairs  and  renewals  of  the  system  may  be  effected.     This 
end  is  accomplished  through  the  agency  of  food7  which  in  all  animals  con- 
sists of  protein  in  its  various  forms  (albumen,  fibrine,  caseine,  etc.),  starch, 
sugar,  gum,  and  fat,  to  which,  in  the  case  of  flesh-eating  animals,  gelatine 
must  be  added.    Pood,  or  nourishment  from  without,  can,  however,  be  only 
made  available  for  the  wants  of  the  system  by  being  first  converted  into 
blood,  and  this  is  effected  through  the  agency  of  various  processes,  which  are 
collectively  termed  digestion. 

826.  Digestion  . — The  various  acts  of  the  function  of  digestion  are  as 
follows : — From  the  mouth,  where  the  food  is  chewed  by  the  teeth  and  moist- 
ened by  the  saliva,  it  passes  into  the  stomach. 

The  saliva  is  secreted  by  glands  which  open  into  the  interior  of  the  mouth, 
and  consists  chiefly  of  water,  holding  in  solution  about  1  per  cent,  of  saline 
matter.  The  quantity  of  saliva  produced  in  a  full-grown,  healthy  man,  in  the 
course  of  24  hours,  varies  from  8  to  21  ounces.  Its  chief  office  seems  to  be 
to  dilute  the  food  and  assist  mastication  and  deglutition ;  but  it  is  also  sup- 
posed to  act  chemically,  through  the  agency  of  a  peculiar  organic  substance 
contained  hi  it,  termed  pytaline,  which,  like  diastase,  is  capable  of  converting 
the  starch  and  gum  of  the  food  into  sugar.  Its  action,  however,  in  this  re- 
spect, is  probably  very  limited. 

The  food,  having  reached  the  stomach,  is  subjected  to  the  action  of  a  pe- 


*  "No  other  component  part  of  the  organism,"  says  Liebig,  "can  be  compared  to 
the  blood,  in  respect  to  the  feeble  resistance  -which  it  offers  to  external  influences.  It  is 
not  an  organ  which  is  formed,  but  an  organ  in  the  act  of  formation ;  indeed  it  is  the  sum 
of  all  the  organs  which  are  being  formed.  The  chemical  force  and  the  vital  principle 
hold  each  other  in  such  perfect  equilibrium,  that  every  disturbance,  however  trifling,  or 
from  whatever  cause  it  may  proceed,  effects  a  change  in  the  blood.  In  fact,  it  possesses 
so  little  permanence*  that  it  can  not  be  removed  from  the  body  without  immediately  suf- 
fering a  change,  and  can  not  come  in  contact  with  any  organ  in  the  body  without  yielding 
to  its  attraction.  The  slightest  action  of  a  chemical  agent  upon  the  blood  exercises  an 
injurious  influence  ;  even  the  momentary  contact  of  the  air  in  the  lungs,  although  ef- 
fected through  the  medium  of  cells  and  membranes,  alters  the  color  and  other  qualities 
of  the  blood.  Every  chemical  action  propagates  itself  through  the  mass  of  the  blood : 
for  example,  the  active  chemical  condition  of  the  constituents  of  a  body  undergoing  de- 
composition, fermentation,  putrefaction,  or  decay,  disturbs  the  equilibrium  of  the  chem- 
ical force,  and  the  vital  principle  in  the  circulating  fluid.  Numerous  modifications  in  the 
composition  and  condition  of  the  compounds  produced  from  the  elements  of  the  blood  re- 
Bult  from  the  conflict  of  the  vital  force  with  the  chemical  affinity,  in  their  incessant  en- 
deavor to  overcome  each  other." 

QUESTIONS.— What  is  the  office  of  food  ?  Of  what  does  the  food  of  animals  conbist  ? 
"What  change  ia  necessary  to  render  food  efficacious  ?  What  is  the  first  process  of  di- 
gestion I  "What  is  the  saliva  2  What  is  its  constitution  2  What  its  action  ! 


ANIMAL    ORGANIZATION    AND    PRODUCTS.      493 

culiar  fluid,  called  the  gastric  juice,  which  flows  out  of  minute  openings  in 
the  inner  surface — or  mucous  membrane,  as  it  is  called— of  the  stomach. 
This  fluid  possesses  the  power  of  dissolving,  at  the  temperature  of  the  body, 
the  nitrogenized  alimentary  principles,  such  as  albumen,  fibrine,  etc.,  but  ex- 
erts no  solvent  action  upon  starchy  or  fatty  substances.  These  last,  however, 
through  the  joint  action  of  the  saliva  and  the  uniform  warmth  and  motion  of 
the  muscular  walls  of  the  stomach,  are  all  brought  into  a  semi-fluid  state.  In 
what  manner  the  gastric  juice  is  enabled  to  effect  the  reduction  of  nitrogen- 
ized food  to  a  nearly  fluid  condition,  is  not  known.  It  is  said  to  contain 
free  hydrochloric  acid,  and  an  organic  principle  called  pepsin,  and  to  the 
joint  influence  of  these  two  the  solvent  power  of  the  gastric  juice  has  been 
attributed.* 

The  amount  of  gastric  juice  secreted  by  the  stomach  of  a  well-fed,  grown 
man,  has  been  estimated  at  from  60  to  80  ounces  in  every  24  hours. 

Digestion  generally  commences  immediately  after  the  introduction  of  food 
into  the  stomach,  and  is  usually  finished  in  about  four  hours — the  food  being 
converted  into  a  grayish,  gruel-like,  slightly  acid  pulp,  called  chyme.  This 
chyme  passes  from  the  stomach  into  the  upper  part  of  the  small  intestines, 
called  the  duodenum,  where  it  is  moistened  by  two  saliva-like  liquids,  the  bile 
and  the  pancreatic  juice,  which  are  secreted  by  peculiar  organs  termed  res- 
pectively the  gall-bladder  and  the  pancreas.  The  action  of  the  bile  on  the 
food  is  not  well  known,  but  the  pancreatic  juice  acts  instantaneously  on  tho 
non-nitrogenous  alimentary  substances,  converting  starch,  etc.,  into  sugar, 
and  the  fatty  matters  into  an  emulsion  which  renders  them  fit  for  absorption. 
After  undergoing  the  action  of  these  liquids,  the  nutritious  matter  presents  a 
uniform  milky  appearance,  and  is  termed  chyle.  In  this  condition  it  is  nearly 
all  absorbed  by  a  system  of  vessels  called  the  lacfeals,  which  terminate  in  a 
common  reservoir — the  thoracic  duct — which  in  man  is  about  the  size  of  a 
large  goose-quill  The  thoracic  duct  terminates  in  a  large  vein  near  the  left 
shoulder,  and  into  this  the  chyle  is  discharged  and  passes  forward  to  tho 
lungs,  where  it  assumes  a  red  color  and  becomes  blood,  f 

*  Some  years  since  a  French  Canadian  by  the  name  of  St.  Martin,  -was  severely  injured 
in  the  side  by  the  explosion  of  a  gun,  but  the  wound  finally  healed,  leaving:  a  permanent 
orifice  in  the  -rails  of  the  stomach  through  -which  food  could  be  introduced,  and  all  the  phe- 
nomena of  the  digestion  observed.  From  the  stomach  of  this  person,  also,  gastric  juice 
has  been  taken  out  by  means  of  a  little  cup,  and  chemically  examined.  Professor  F.  S. 
Smith,  of  the  Pennsylvania  Medical  College,  who  examined  the  gastric  juice  thns  obtained 
in  1857,  states  that  it  contains  hardly  any  hydrochloric  acid,  but  much  lactic  acid ;  and  to 
this  latter  agent  he  ascribes  the  constant  acid  reaction  of  the  stomach.  It  has  also  been 
shown  by  observations  made  through  this  subject,  that  the  food  introduced  into  the  stom- 
ach is  caused  to  revolve  continually  around  its  interior,  the  revolutions  requiring  a  period 
of  from  one  to  three  minutes. 

t  It  is  not  to  be  understood  that  all  food  lingers  in  the  stomach  for  the  space  of  several 

QUESTIONS.— What  change  does  the  food  undergo  in  the  stomach  ?  What  is  the  gastric 
juice  ?  What  quantity  of  gastric  juice  is  secreted  by  the  stomach  ?  What  period  is  usu- 
ally required  for  digestion  ?  What  is  chyme  ?  What  takes  place  when  the  food  leaves 
the  stomach  ?  What  is  the  function  of  the  bfle  and  pancreatic  juices?  What  is  chyle? 
What  becomes  of  the  chyle  ? 


494  ORGANIC     CHEMISTRY. 

That  part  of  the  food  (chyle)  which  is  insoluble,  or  unfit  for  assimilation,  is 
left  unabsorbed  by  the  lacteals,  and  passes  oft'  through  the  intestines  in  the 
form  of  excrementitious  matter.  ''How  effectual  the  digestive  process  is  in 
exhausting  what  we  eat  of  its  nutritive  matter  may  be  judged  of  from  the 
fact,  that  a  healthy,  grown  man,  fed  with  ordinary  diet,  rejects  of  undigested 
and  of  wasted  or  used  up  matter,  both  taken  together,  only  from  four  to  six 
ounces.  And  this  rejected  matter  consists  of — 

Water 3    to  4J  oz. 

Organic  matter OJ  to  1£   " 

Mineral  matter,  chiefly  phosphates Oi  to  Of    " 

Total 4    to  6    oz. 

Or  he  discharges  one  to  one  and  a  half  ounces  of  dry  solid  matter  daily." — 
JOHNSON.* 

826.  Respiration . — All  animals  as  well  as  vegetables  require,  for  the 
proper  performance  of  their  various  functions  and  their  continued  existence 
in  a  living  state,  a  free  supply  of  atmospheric  air  as  well  as  a  supply  of  food. 
It  is  also  necessary  that  this  air  should  have  free  access  to  the  interior  of  their 
structure,  and  the  act  or  process  by  which  this  is  accomplished  is  termed 
Respiration, 

The  organs  by  which  the  act  of  respiration  is  performed  differ  essentially 
in  different  species  of  animals.  In  the  lowest  types  of  the  animal  kingdom, 
as  the  polypes,  respiration  is  accomplished  exclusively  through  the  skin.  In- 
sects also  draw  in  air  into  then*  system,  or  in  other  words,  breath,  by  means 
of  organs  called  trachece,  or  wind-pipes — tubes  which  penetrate  in  various 
directions  through  their  bodies,  and  terminate  externally  in  little  orifices 
called  stomata.  If  we  smear  the  body  of  an  insect,  as  a  wasp,  with  thick  oil, 
we  close  up  the  stomata,  and  the  insect  speedily  dies  of  suffocation.  All 
vertebrate  animals  are  endowed  with  localized  organs  of  respiration,  which 
are  termed  lungs,  or  gills.  In  man  and  the  higher  animals,  the  "  lungs  con- 
sist of  two  rounded,  oblong,  somewhat  flattened  masses,  of  very  cellular  sub- 
stance, situated  in  the  cavity  of  the  chest,  and  communicating  with  the  at- 


hours.  Soups  and  nutritious  fluids  which  require  no  "breaking  down"  in  the  stomach, 
pass  from  the  stomach  into  the  intestines  in  a  very  short  period.  Neither  is  nutriment 
taken  up  wholly  through  the  lacteals  of  the  intestines,  but  a  certain  portion,  in  a  fluid 
state,  by  the  action  of  endosmotic  force,  passes  through  the  walls  of  the  stomach,  and  is 
mingled  with  the  general  blood. 

*  The  cause  of  the  peculiar  odor  of  fcecal  matter  is  in  great  measure  unknown,  although 
scientific  ardor  has  induced  some  chemists  to  undertake  most  repulsive  investigations  with 
a  view  of  obtaining  information  on  the  subject.  By  treating  fresh  night  soil  with  alcohol 
two  principles  have  been  extracted,  viz.,  a  crystalline,  slightly  alkaline  substance,  named 
esxretine,  and  an  acid  called  excretolic  acid ;  but  little,  however,  is  known  concerning  them. 
It  has  also  been  ascertained  that  when  albuminous  compounds  are  heated  with  hydrate 
of  potash,  and  the  residue  distilled  with  sulphuric  acid,  an  odor  characteristic  in  an  in- 
tense degree  of  fecal  matter  is  produced. 

QUESTIONS. — "What  becomes  of  the  unassimilated  matter  ?  What  is  respiration?  How 
is  respiration  effected  in  different  animals  ?  What  is  the  constitution  of  the  lungs  in  man 
and  the  higher  animals  f 


ANIMAL    ORGANIZATION     AND     PRODUCTS.      495 


FlG.  242. 


rnospherc  through  the  wind- 
pipe, or  trachea).  The  general 
form  of  the  human  lungs  is 
represented  in  Fig.  242.  Tho 
air  or  wind-pipe,  a  &,  as  it  de- 
scends from  the  throat,  branch- 
es off  into  large  (bronchial) 
tubes,  c  c,  and  these  again  into 
smaller  and  still  smaller,  and 
finally  into  hair-like,  or  capil- 
lary vessels.  These  capillary 
tubes,  in  turn,  communicate 
with  little  air-cells  contained 
in  an  elastic  membrane,  so 
minute  that  the  number  exist- 
ing in  the  lungs  of  a  full-grown 
man  is  estimated  at  600  mil- 
lions, and  between,  or  imbed- 
ded in  these  cells,  blood-vessels 
equally  minute  are  distributed 
in  every  direction.  Tho  ap- 
pearance of  the  air-cells  and  blood-vessels  of  the  lungs,  as  seen  tinder  the 
microscope,  is  represented  in  Fig.  243. 

The  motion  of  the  lungs  in  respiration  is  analogous 
to  the  motion  of  the  leather  of  a  pair  of  bellows. 
When  we  inhale,  the  cavity  of  the  chest  or  thorax  ia 
expanded  by  muscular  action,  and  a  vacuum  is  formed 
around  the  lungs,  in  consequence  of  which  the  exter- 
nal air  instantly  rushes  in  and  penetrates  to  the  re- 
motest parts  of  the  cellular  substance.  When  we  ex- 
hale* the  thorax  contracts,  and  the  air  contained  in  tho 
lungs  is  expelled,  the  muscles  of  tho  wind-pipe  at  the 
same  time  contracting  in  order  to  assist  the  process. 
In  ordinary  respiration,  a  man  makes  17  or  18  respi- 
rations per  minute,  during  each  of  which  ho  draws 
in  about  20  cubic  inches  of  air,  or  between  3  and  4 
thousand  gallons  per  day.  In  man  also  the  skin  is  to 
some  extent  a  respiratory  organ,  through  wliich  air 
enters  and  escapes,  as  it  docs  from  the  air-vessels  of 
the  lungs,  though  less  rapidly.* 


FiG.  243. 


*  When  a  portion  of  the  skin  has  been  burned,  it  is  no  longer  capable  of  exercising  the 
Function  of  respiration,  and  the  lungs  are  therefore  obliged  to  perform  extra  duty,  and 
Buffer  in  consequence.  Hence  diseases  of  the  lungs  arc  a  frequent  result  of  extensive 
burns. 

QUESTIONS.— What  is  the  mechanical  action  of  breathing  ?  What  amount  of  air  enters 
the  lungs  by  respiration  ?  Is  the  skin  a  respiratory  organ  ? 


496  OBGANIC    CHEMISTKY. 

The  composition  of  the  air  which  escapes  from  the  lungs  is  not  the  samo 
as  that  which  enters,  and  is  found  to  contain  a  greatly  increaeed  quantity  of 
carbonic  acid  and  vapor  of  water,  and  a  diminished  percentage  of  oxygen ; 
the  quantity  of  nitrogen,  however,  remains  nearly  unaltered. 

The  amount  of  pure  carbon  which  is  thrown  off  from  the  lungs  of  a  full-grown 
man,  in  the  form  of  carbonic  acid,  in  a  space  of  24  hours,  varies  from  5  to 
15  ounces ;  while  the  quantity  which  escapes  from  the  skin  also  during  the 
same  period,  by  respiration,  is  estimated  at  from  50  to  60  grains.  Tho 
amount  of  water  exhaled  from  the  lungs  and  skin  in  24  hours  probably 
averages  about  3  or  4  pounds. 

The  lungs  extract  or  absorb  from  the  air  which  enters  them  from  one 
seventh  to  one  fifth  of  its  oxygen,  and  the  absolute  weight  of  the  oxygen 
thus  introduced  into  the  system  in  a  day,  is  estimated  to  be  equal  to  about 
one  fourth  of  the  weight  of  the  whole  food,  solid  and  liquid,  which  an  ani- 
mal consumes.  The  absorption  of  oxygen  takes  place  in  the  minute  air- 
cells  of  the  lungs,  through  the  thin  membraneous  walls  of  which  it  passes  by 
the  action  of  endosmosis  into  the  adjacent  blood-vessels,  and  combines  with 
the  blood  contained  in  them,  imparting  to  it  the  bright  scarlet  color  which  is 
characteristic  of  arterial  blood. 

827.  Uses  of  Respiration . — From  what  has  been  already  said,  it 
must  appear  evident  that  the  principal  object  of  respiration  is  to  introduce 
oxygen  into  the  blood,  which  contains  the  nutritive  portion  of  the  food  taken 
into  the  stomach.  The  purpose  which  oxygen  subserves  in  the  blood  is 
three-fold  :— 

I.  It  assists  in  'building  up  the  substance  of  the  "body.     The  composition  of 
gluten,  albumen,  and  the  other  nitrogenized  vegetable  principles,  is,  as  ha3 
been  before  stated,  very  nearly  the  same  as  that  of  the  corresponding  prin- 
ciples in  animal  tissues ;  yet  chemical  investigations  have  shown  that  the 
former  require  to  be  combined  with  a  certain  proportion  of  oxygen  before 
they  can  become  incorporated  in  the  substance  of  the  body.     This  oxygen 
is  supplied  through  the  lungs,  but  the  quantity  thus  used  for  restorative  pur- 
poses is  small 

II.  It  assists  in  removing  waste  and  effete  matters  from  the  system.     The 
expenditure  of  every  kind  of  force  in  the  animal  system  is  accompanied  by, 
or  requires  an  expenditure   or  change  in  animal  matter.     The  particles  of 
matter  which  have  once  undergone  such  change,  or  have  once  discharged 
their  functions,  become  inoperative,  or  waste,  and  their  removal  from  the  sys- 
tem is  necessary  to  a  continuance  of  healthy  action.     Now  the  agent  which 
mainly  effects  the  change  in  the  first  instance,  and  removal  of  the  waste  prc- 

QTTESTIONS.— -What  is  the  composition  of  the  air  which  escapes  from  the  lungs?  What 
amount  of  carbon  passes  from  the  system  by  respiration?  What  amount  of  water  is  ex- 
haled from  the  longs  and  skin  ?  What  proportion  of  oxygen  is  absorbed  by  the  lungs 
from  the  air  ?  In  what  part  of  the  lungs  does  the  absorption  of  oxygen  take  place  ?  What 
is  the  use  of  respiration  ?  What  purpose,  subserved  by  oxygen  in  the  blood,  is  first  men- 
tioned ?  What  is  the  second  end  attained  to  2  How  does  oxygen  remove  waste  matterg 
from  the  system  ? 


ANIMAL    ORGANIZATION    AND  PRODUCTS.      497 

ducts  in  the  second,  is  the  oxygen  absorbed  by  the  blood  in  the  lungs. 
Thus  muscle,  by  the  addition  of  oxygen,  becomes  decomposed,  and  passes  in 
a  state  of  solution  into  the  veins,  from  whence  it  is  secreted  by  various  organs, 
and  finally  thrown  out  from  the  system. 

Urine  . — The  channel  through  which  most  of  the  products  of  the  de- 
composition of  the  azotized  bodies  and  many  of  the  waste  mineral  salts  pass 
out  of  the  body,  is  the  urine.  This  liquid,  which  is  secreted  by  the  kid- 
neys from  the  blood,  also  serves  to  remove  any  superfluous  water  from  the 
system.  Its  principal  constituents  are  two  complex  organic  substances 
termed  urea  and  uric  acid,  which  are  composed  of  carbon,  hydrogen,  nitro- 
gen, and  oxygen,  and  readily  furnish  by  their  decomposition  various  salts  of 
ammonia.  In  addition  to  these  products,  urine  contains  phosphates  of  lime, 
magnesia,  and  soda,  sulphates  of  potash  and  soda,  chloride  of  sodium,  lactic 
acid,  and  certain  imperfectly  known  organic  principles,  including  a  coloring 
and  an  odoriferous  substance.  All  these  substances  exist  in  the  urine  dis- 
solved in  water,  which  constitutes  more  than  nine  tenths  by  weight  of  the 
whole  secretion. 

III.  The  absorption  of  oxygen  produces  animal  heat.  This  is  accomplished 
by  the  oxydation  or  combustion  of  the  constituents  of  the  non-nitrogenized 
food  existing  in  the  blood.  The  reasons  which  lead  us  to  this  inference  may 
be  briefly  stated  as  follows : — 

If  a  fat  animal  be  deprived  of  nourishment  for  some  days,  it  will  rapidly 
diminish  in  weight.  This  result  is  the  necessary  consequence  of  the  fact, 
that  the  animal  is  continually  throwing  off  carbonic  acid  and  water  from  the 
lungs  and  skin,  and  urea  and  mineral  constituents  through  the  excretory 
organs,  and  receiving  no  food  to  replace  them. 

If  we  examine  the  condition  of  an  animal  after  this  period  of  starvation,  we 
find  the  loss  of  weight  and  substance  is  most  remarkable  in  the  fat  of  the 
body,  which  has  diminished  in  far  greater  proportion  than  any  of  its  other 
constituent  substances.  Careful  examination  also  shows  that  this  fat  has 
not  passed  off  as  liquid  or  solid  excrement,  but  has  been  converted  in  the 
blood,  by  oxydation,  into  carbonic  acid  and  water,  and  in  this  condition  has 
been  breathed  away  through  the  lungs  and  skin.  If,  however,  instead  of 
starving  the  animal,  we  give  it  abundance  of  fat  in  its  food,  then  the  fat  of 
its  own  body  will  suffer  no  diminution,  but  the  oxygen  taken  into  the  blood 
will  transform  the  fat  of  the  food  into  carbonic  acid  and  water,  and  these  will 
be  breathed  out  of  the  lungs  as  before.  The  same  end  will  also  be  attained 
if  instead  of  fat  we  give  food,  like  starch  and  sugar,  which  is  analogous  to 
fat  in  its  composition. — JOHNSON. 

Now  when  carbon  and  hydrogen  compounds,  i.  e.,  fat,  starch,  sugar,  etc., 
are  oxydized  or  burned  in  the  open  air,  carbonic  acid  and  vapor  of  water  are 
produced,  and  heat  is  evolved.  The  same  action  must  necessarily  be  attended 
with  the  same  results  in  the  body,  and  we  have,  therefore,  an  explanation  of 

QUESTIONS.— What  is  urine  ?  What  is  the  composition  of  this  secretion  ?  What  third 
purpose  is  subserved  by  oxygen?  How  does  the  absorption  of  oxygen  occasion  animal 
heat?  What  reasons  lead  to  this  inference  ? 


498  ORGANIC     CHEMISTRY. 

the  phenomenon  of  animal  heat  Furthermore,  all  experiments  show  that  the 
amount  of  heat  generated  by  burning  (oxydating)  a  certain  quantity  of  fat, 
etc.,  is  the  same,  whether  the  combustion  takes  place  in  a  furnace  or  in  the 
animal  system. 

The  oxydation  of  fat  and  the  other  constituents  of  the  blood  is  supposed  to 
take  place  mainly  in  the  minute  vessels  or  passages,  termed  capillary  vessels, 
which  unite  the  ultimate  subdivisions  of  the  veins  and  arteries,  and  are  dis- 
tributed over  every  part  of  the  body  where  nervous  influence  is  perceptible. 
Jn  these,  the  arterial  blood,  coming  from  the  lungs  and  possessing  a  scarlet 
color,  gives  up  its  oxygen  to  the  substances  with  which  it  is  brought  in  con- 
tact, and  receives  in  return  the  products  of  oxydation,  carbonic  acid  and 
water.  It  also  changes  in  color  from  a  bright  to  a  dark  red,  and  returning 
through  the  veins  to  the  lungs,  through  the  action  of  the  heart,  passes 
into  the  minute  blood-vessels  of  the  lungs,  which  are  surrounded  by  the  air- 
cells.  Here  the  carbonic  acid  and  excess  of  water  pass  out  through  the 
walls  of  the  membraneous  tissue  inclosing  them  through  endosmotic  action, 
and  by  the  act  of  exhalation  are  forced  into  the  air ;  while  -at  the  same  time 
oxygen  from  without  is  by  similar  means  carried  inward,  and  the  blood,  re- 
stored to  its  arterial  condition,  returns  upon  its  circuit  to  eSect  the  same 
changes  and  undergo  the  same  transformation. 

Animals  whose  respiratory  organs  are  small  and  imperfect,  and  which,  there- 
fore, consume  but  a  comparatively  small  amount  of  oxygen,  possess  a  bodily 
temperature  but  little  elevated  above  that  of  the  medium  in  which  they  live ; 
animals,  on  the  contrary,  whose  lungs  are  large  in  proportion  to  their  bodies, 
and  respire  frequently,  possess  the  highest  bodily  temperature.  In  man, 
the  mean  temperature  of  the  body  is  about  98°  F.  The  temperature  of  a 
healthy  child,  who  consumes  proportionally  more  oxygen  and  respires  more 
frequently  than  an  adult  person,  is  somewhat  higher,  102°  F.  In  birds  the 
temperature  is  from  104°  to  108°  F.  The  temperature  of  the  same  animal 
also  at  different  times,  varies  with  the  activity  of  the  respiration.  "When  the 
blood  circulates  slowly,  and  the  temperature  is  low,  the  quantity  of  oxygen 
consumed  is  comparatively  small ;  when,  on  the  contrary,  the  circulation  by 
vigorous  exercise  or  labor  is  accelerated,  a  large  quantity  of  oxygen  disap- 
pears, and  the  animal  heat  rises. 

828.  Nature  and  Functions  of  Food , — A  careful  consider- 
ation of  all  the  facts  connected  with  the  subjects  of  nutrition  and  respiration, 
has  led  to  the  division  of  all  animal  nutriments  into  two  great  classes,  viz., 
those  which  are  devoted  to  the  repair  and  nutriment  of  the  body,  and  those 
whose  duty  it  is  to  furnish  animal  heat  by  combustion  in  the  blood.  The 
former  have  been  termed  by  Liebig  the  plastic  elements  of  nutrition,  and  the 
latter  the  elements  of  respiration. 

QUESTIONS Explain  the  manner  in  which  the  oxydation  of  matter  takes^lace  through 

the  circulation.  What  relation  exists  between  the  frequency  of  respiration  and  the  ani- 
mal temperature?  How  does  vigorous  exercise  increase  the  temperature  of  the  system? 
Into  what  two  classes  are  all  animal  nutriments  divided  ?  What  are  called  plastic  ele- 
ments of  nutrition  ? 


ANIMAL    ORGANIZATION    AND    PRODUCTS.      499 

The  substances  included  in  the  first  class  are  exclusively  the  protein  com- 
pounds, viz.,  vegetable  fibrine  (gluten),  vegetable  albumen,  vegetable  caseine,  ani- 
mal flesh  and  blood.  These  only  have  the  power  of  reproducing  muscular 
and  nervous  material,  and  these  only  can  afford  nourishment  and  support  in 
the  strict  sense  of  the  term.  In  a  state  of  great  purity,  these  bodies,  however, 
are  not  alone  sufficient  for  the  due  maintenance  of  the  vital  powers.  The  ex- 
periment has  been  frequently  tried  on  animals,  and  always  with  a  negative 
result.  Certain  of  the  non-azotized  substances,  and  certain  saline  compounds 
which  are  always  present  in  natural  food,  are  also  required. 

The  elements  of  respiration  are  fat,  starch,  gum,  sugar,  alcohol,  etc.  Gelatine 
also  probably  belongs  to  this  class,  inasmuch  as  it  has  never  been  found  in 
the  blood,  and  is  supposed  to  be  converted  in  the  process  of  digestion  into 
sugar  and  ammonia  compounds.  These  substances  alone,  are  still  less  capa- 
ble of  supporting  life  than  the  simple  protein  principles. 

829.  The  quantity  of  food  required  by  an  animal  for  purposes  of  nutrition 
or  respiration  varies  greatly  under  different  circumstances.     When  the  waste 
of  muscular  or  nervous  material  is  great,  a  large  supply  of  nitrogenized  food, 
or  that  rich  in  the  elements  of  nutrition  will  be  required.     When  the  body  is 
exposed  to  severe  cold  or  to  violent  exercise,  the  loss  must  be  met  by  a  pro- 
portionate increase  in  food  rich  in  the  elements  of  respiration.     In  the  food 
most  abundantly  provided  by  nature  for  animals,  the  cereal  grains,  vegetables, 
and  ordinary  meat,  both  forms  of  nutriment  abound.     In  tropical  countries, 
where  the  loss  of  animal  heat  is  small,  and  where  muscular  power  and  mo- 
tion are  less  required  and  employed,  the  waste  of  the  body  is  greatly  dimin- 
ished, and  a  comparatively  small  quantity  of  food,  both  for  fuel  and  nourish- 
ment, is  required.     The  inhabitants  of  such  countries,  therefore,  live  mainly 
on  rice  and  fruits — substances  which  contain  a  large  amount  of  oxygen,  and 
are  therefore  less  adapted  to  furnish  animal  heat  by  oxydation  in  the  blood. 
The  desire  for  animal  food,  under  such   circumstances,  is  very  slight,  and  is 
sometimes  altogether  absent.     In  cold  countries,  on  the  contrary,  a  greater 
quantity  of  the  elements  of  respiration  is  needed  to  generate  the  proper 
amount  of  heat,  and  at  the  same  time,  as  the  air  is  much  colder  and  therefore 
more  condensed,  a  larger  quantity  of  oxygen  is  taken  into  the  lungs  at  each 
inspiration.     The  inhabitants  of  such  countries,  therefore,  consume  enormous 
quantities  of  food  of  a  fatty  nature — substances  rich  in  hydrogen  and  emi- 
nently combustible,  and  which,  weight  for  weight,  generate  a  larger  amount 
of  heat,  when  oxydated  or  burned  in  the  blood,  than  any  other  products  that 
can  be  taken  as  food.     Navigators  exposed  to  the  intense  cold  of  the  Arctic 
regions,  share  to  a  certain  extent  with  the  Esquimaux,  the  same  liking  for 
blubber  and  train  oil,  which  in  milder  latitudes  they  regard  with  aversion. 

830.  The  fat  and  oils  found  in  animal  tissues  appear  to  bo  stores  of  respi- 

QTJESTIONS.— Can  these,  substances  in  a  state  of  purity  alone  suffice  for  food  ?  What 
are  the  elements  of  respiration  ?  What  is  said  of  the  quantity  of  food  required  by  ani- 
mals for  the  purposes  of  nutrition  or  respiration  ?  What  effect  has  climate  on  the  wants 
of  the  system  ?  What  is  said  of  the  accumulation  of  fat  and  oils  in  the  animal  system  ? 


500  ORGANIC    CHEMISTRY. 

ratory  food,  laid  up  by  nature  against  time  of  need.  They  accumulate  most 
in  the  system  when  lat  itself,  or  the  compounds  containing  its  elements,  are 
supplied  in  excess  as  food,  and  when  the  animal,  through  lack  of  active  exer- 
tion, absorbs  but  little  oxygen,  and  consequently  experiences  but  little  waste.* 

When  the  supply  of  food  is  wholly  withheld  from  the  animal,  the  fat,  as 
the  most  combustible  substance,  and  the  one  most  capable  of  supplying  car- 
bon and  hydrogen  to  meet  the  wants  of  respiration,  rapidly  disappears.  When 
this  has  all  been  consumed,  the  muscles  are  next  attacked,  and  last  of  all  the 
substance  of  the  brain  and  nerves ;  then  insanity  intervenes,  and  the  animal 
dies,  like  a  lamp  or  candle  that  has  been  burnt  out. 

831.  The  main  difference  between  beef  and  bread,  which  two  substances 
may  be  regarded  as  the  representatives,  or  types  of  animal  and  vegetable 
food,  are,  first,  that  the  flesh  does  not  contain  starch,  which  is  so  large  an  in- 
gredient in  vegetable  products ;  and  second,  that  the  proportion  of  flbrine  in 
ordinary  flesh  is  about  three  times  greater  than  its  corresponding  element, 
gluten  (vegetable  fibrine),  is  in  bread.  It  therefore  follows,  that  a  pound  of 
beef-steak  is  as  nutritive  as  three  pounds  of  wheaten  bread,  in  so  far  as  the 
nutritive  value  of  food  depends  upon  this  one  ingredient.  In  meat,  also,  fat 
to  a  certain  extent  represents  and  replaces  the  starch  of  vegetable  food. 

The  relative  nutritive  value  of  the  different  meats  is  as  follows :  beef  is  the 
most  nutritious,  then  chicken,  pork,  mutton,  and  veal.  Of  vegetable  produc- 
tions, the  cereals  generally  rank  first  as  respects  nutritive  value  ;  after  them 
come  the  seeds  of  leguminous  plants,  peas,  beans,  etc. ;  then  the  cabbage,  onion, 
turnips,  carrots,  potatoes,  rice,  and  watery  fruits.  "  The  dried  potato  is  less 
nutritive,  weight  for  weight,  in  the  sense  of  supporting  the  strength  and  en- 
abling a  man  to  undergo  fatigue,  than  any  other  extensively  used  food  of 
which  the  composition  is  known,  with  the  exception  of  the  rice  and  of  the 
plantain."  Fish  in  general  contains  more  fibrine  and  less  fat  than  flesh-meat, 
and  is  highly  nutritious. 

Salted  meat  is  less  nutritious  than  fresh  meat.  The  application  of  salt  to 
meat  causes  the  fibers  to  contract,  and  the  juices  to  flow  out  from  its  pores. 
Hence  fresh  flesh  over  which  salt  has  been  strewed  is  found,  after  the  lapse 
of  a  little  time,  to  be  swimming  in  its  own  brine,  although  not  a  drop  of 
water  has  been  added.  The  juice  thus  extracted  contains  a  large  proportion 
of  the  nutritive  constituents  of  the  meat,  i.  e.,  albuminous  compounds,  with 
the  alkaline  and  earthy  phosphates.  Hence  the  continued  and  exclusive  use 
of  salt  provisions  occasion  a  disease  called  the  scurvy,  in  which  the  blood 
becomes  impaired  mainly  through  a  lack  of  the  soluble  mineral  salts  which  are 
removed  from  the  meat  by  the  brine. 

*  This  principle  is  applied  in  the  fattening  of  animals,  by  compelling  them  to  remain 
inactive  by  confinement  in  stalls  or  pens,  and  at  the  same  time  supplying  them  plenti- 
fully with  rich,  oily  food.  ^ 

QUESTIONS.— What  takes  place  when  the  animal  is  deprived  of  food  ?  What  is  the  dif- 
ference between  beef  and  bread  as  respects  nutritive  qualities  ?  What  is  the  relative 
values  of  different  meats  and  vegetables?  What  is  said  of  salted  meat  ? 


ANIMAL    ORGANIZATION    AND    PRODUCTS.       501 

The  preservation  of  fresh  meat  by  salting  is  due  to  a  separation  of  its 
water,  to  an  exclusion  of  air  through  a  contraction  of  the  fibers  of  the  meat, 
and  upon  the  formation  of  a  compound  of  the  flesh  and  the  salt,  which  does 
not  readily  undergo  decay. 

832.  Relation    between    Animals    and    Plants . — All  the 
various  forms  of  matter  which  are  essential  to  the  existence  of  living  organ- 
isms are  hi  a  constant  state  of  circulation.     Thus,  the  essential  constituents 
in  the  formation  of  vegetable  products  are  carbonic  acid,  ammonia,  and  water. 
Plants  absorb  these  from  the  soil  or  from  the  atmosphere,  and,  under  the  in- 
fluence of  sun-light  and  the  vital  principle,  rearrange  and  organize  them  into 
vegetable  tissue,  starch,  sugar,  fat,  and  the  protein  compounds.     These  sub- 
stances constitute  the  food  of  animals,  and  after  employment  in  their  systems, 
and  after  passing  through  various  decompositions,  they  are  again  restored  to 
the  earth  and  the  atmosphere  in  the  form  of  carbonic  acid,  water,  and  ammo- 
nia :  and  are  once  more  rendered  capable  of  assimilation  by  plants.     Thus  an 
uninterrupted  and  perpetual  chain  of  vital  phenomena  is  established  from  in- 
animate matter  to  the  living  plant,  and  from  the  h'ving  plant  to  the  living, 
sentient  animal,  and  the  products  of  one  order  of  beings  become  the  suste- 
nance of  the  other. 

833.  Conclusion  . — "  "What  has  been  called  organic  chemistry  is  no- 
thing but  a  name,  and  a  wrong  one.     There  is  really  no  such  science ;  it  is 
only  the  chemistry  of  inorganic  forms,  of  substances  that  have  been  living 
but  are  now  dead — of  the  mere   refuse  and  remains  of  organization.     The 
composition  of  those  favored  materials  from  which  the  vegetable  world  weaves 
its  tissues — water,  carbonic  acid,  and  ammonia — is  known.     The  composition 
of  the  proximate  principles  which  are  extractablo  by  easy  processes  from  dead 
plants  and  animals,  is  also  known.     But  the  composition  of  the  truly  living 
tissues  neither  is,  nor  can  be  understood.     They  die  the  moment  chemistry 
puts  her  finger  on  them.     She  can  trace  the  constructive  elements  into  the 
structure  of  the  living  animal  or  plant,  and  out  of  it,  but  not  in  it.     What 
may  be  their  mode  of  arrangement,  or  of  their  possible  ingredients  in  matter 
which  is  genuinely  alive,  scientific  investigation  fails  to  reveal.     The  living 
frame  of  the  meanest  animal  or  plant  is  sacred  and  enchanted  ground,  where 
the  chemist  can  only  take  the  shoes  off  his  feet  and  confess  the  sanctity  and 
inviolability  of  life." 

QUESTIONS.— How  does  salt  preserve  meat  ?  What  is  said  of  the  relation  of  animals 
and  plants?  What  does  organic  chemistry  really  consider  ?  Do  we  actually  know  the 
composition  of  a  living  tissue  ? 


APPENDIX. 


Apparatus  — The  apparatus  essential  for  illustrating  and  facilitating 
the  study  of  chemistry,  need  not  be  of  necessity  expensive  or  complex.  With 
the  somewhat  popular  idea,  however,  that  a  course  of  experimental  chem- 
istry can  be  successfully  conducted  with  an  apparatus  improvised  from  a  few 
bottles,  tobacco-pipes,  and  glass  tubing,  the  author  has  no  sympathy.  Chem- 
ical experiments  are  most  easily  and  successMly  performed  with  apparatus 
especially  constructed  for  the  purpose,  and  what  is  saved  in  expense  by 
using  imperfect  and  unsuitable  materials,  will  be  more  than  lost  in  time  and 
vexation  of  spirit.  It  is  no  doubt  true  that  many  eminent  chemists  have  in- 
stituted important  investigations,  and  performed  brilliant  experiments,  with 
exceedingly  simple  or  imperfect  apparatus ;  but  it  is  also  equally  true,  that 
the  tact  and  ability  required  to  overcome  the  inherent  difficulties  of  such  an 
undertaking,  have  been  deemed  sufficiently  singular  to  occasion  especial 
comment.  In  short,  it  is  only  the  operator  rendered  skillful  by  long  expe- 
rience and  practice  who  is  able  to  work  successfully  in  chemistry  with  poor 
materials,  and  not  the  tyro. 

We  believe,  therefore,  the  most  practical  advice  that  can  be  given  to  teachers 
and  students  who  are  lacking  in  experience,  is  to  procure  the  very  best  appa- 
ratus their  resources  will  admit  of,  as  being  hi  the  end  the  cheapest  and  most 
serviceable. 

In  purchasing  apparatus  it  will  be  found  advisable,  also,  to  first  send  to 
some  one  or  more  of  the  prominent  dealers  hi  Boston,  New  York,  or  Phila- 
delphia, for  an  illustrated  and  priced  catalogue  of  their  stock.  In  this  way 
the  purchaser  will  be  enabled  to  make  his  selections  most  judiciously  and 
economically. 

The  following  articles  will  be  found  most  serviceable  and  indispensable  for 
a  short  course  of  chemical  experimentation : — A  copper  flask,  with  adjustable 
tube  and  collar,  for  generating  oxygen  gas;  a  retort  stand  with  movable 
rings  of  various  sizes ;  a  glass  (4  oz.)  spirit-lamp;  2  dozen  test  tubes  and 
stands;  2  wide-mouth,  stoppered  glass  jars,  or  receivers;  2  tail  and  plain 
cylindrical  air-jars  (see  Fig.  87) ;  4  to  6  flat-bottom,  thin  glass  flasks,  suitable 
for  generating  hydrogen,  hydrosulphuric  and  carbonic  acid  gases  (see  Figs. 
101,  126,  130);  1  one  quarter  pint  stoppered  retort  and  receiver ;  1  one  half 
pint  do.,  plain ;  a  gas-bag,  provided  with  stop-cock  and  bubble-pipe ;  a  set 
of  small  porcelain  basins ;  glass  tubing  and  small  glass  rods  for  stirrers,  etc. ; 


APPENDIX.  503 

2  small  glass  funnels ;  a  deflagrating  ladle  or  spoon ;  a  small  wedge-wood 
mortar  and  pestle ;  a  blow-pipe ;  platinum  foil  and  wire ;  filtering-paper ; 
test  papers ;  set  of  cork-borers  ;  a  steel  spatula ;  a  strip  of  sheet  caoutchouc ; 
a  round  and  a  three-cornered  file  for  filing  corks,  cutting  glass  tube,  etc. ;  a 
nest  of  earthen  crucibles ;  and  two  small  porcelain  crucibles. 

A  pair  of  gasometers,  oxygen  and  hydrogen,  arranged  in  such  a  way  as  to 
admit  of  being  used  conjointly  as  a  compound  blow-pipe  (see  Fig.  102)  are  al- 
most indispensable.  They  are  now  made  of  small  size,  and  at  a  very  moder- 
ate expense,  and  constitute  an  exceedingly  durable,  serviceable,  and  orna- 
mental article  of  laboratory  furniture.  A  Berzelius  spirit-lamp  (see  Fig.  173) 
will  obviate,  to  a  great  degree,  the  necessity  of  ever  using  a  furnace.  The 
operator  can  easily  arrange  a  pneumatic  trough  after  any  of  the  models  given 
on  page  197,  to  suit  his  own  convenience. 

In  addition  to  the  articles  thus  specified,  there  are  many  others,  such  as  a 
small  galvanic  battery,  an  apparatus  for  decomposing  water,  specific  gravity 
bottles,  thermometers,  scales  and  weights,  etc.,  etc.,  the  necessity  for  which 
will  depend  in  a  great  measure  upon  the  extent  and  fullness  of  the  course 
of  experimentation  prescribed  or  adopted. 

In  regard  to  chemical  reagents,  the  following  is  a  list  of  the  more  impor- 
tant :  the  acids,  sulphuric,  hydrochloric,  nitric,  acetic  and  oxalic ;  potassium, 
sodium,  ammonia  (aqua),  carbonate  of  ammonia,  sal-ammoniac,  phosphorus, 
caustic  potash,  carbonate  of  soda,  black  oxyd  of  manganese,  chlorate  of  pot- 
ash, alum,  sulphur,  bone-black,  iodine,  bleaching  powder,  acetate  (sugar)  of 
lead,  iodide  of  potassium,  sulphate  of  copper  (blue  vitriol),  sulphate  of  iron 
(green  vitriol),  borax,  bi-chromate  of  potash,  ferrocyanide  of  potassium  (yel- 
low prussiate  of  potash),  fluor  spar,  arsonious  acid,  metallic  antimony,  fine 
iron-wire,  sheet  zinc,  tin  foil,  copper  turnings,  chloride  of  barium,  chloride  of 
strontium,  lime  water,  metallic  mercury,  chloride  of  mercury  (corrosive  subli- 
mate), saltpeter,  nitrate  of  silver,  alcohol,  ether,  and  bees- wax. 

Of  the  above-mentioned  reagents,  it  is  recommended  to  have  the  following 
(in  solution)  arranged  upon  a  convenient  stand,  or  tray,  in  clear  glass  bottles, 
fitted  with  ground  glass  stoppers,  and  of  the  capacity  of  about  a  half  pint : 
sulphuric  acid  dilute ;  do.  strong  (oil  of  vitriol) ;  nitric  dilute ;  do.  concen- 
trated ;  hydrochloric  acid ;  acetic  acid ;  oxalic  acid ;  aqua  ammonia ;  carbonate 
of  ammonia ;  chloride  of  ammonium  (sal  ammoniac) ;  chloride  of  barium  ; 
lime  water ;  caustic  potash ;  caustic  soda ;  carbonate  of  soda ;  sulphate  of 
copper ;  ferrocyanide  of  potassium  ;  chlorine  water ;  chloride  of  mercury  (cor- 
rosive sublimate) ;  bi-chromate  of  potash ;  sulphiudigotic  acid  ;  acetate  of 
lead ;  perchloride  of  iron ;  alcohol  and  ether.  Also  the  following  in  solution 
in  1  or  2  ounce  bottles :  iodide  of  potassium  ;  nitrate  of  silver ;  chloride  of 
platinum.  Reagent  bottles  suitable  for  this  purpose,  with  printed  labels  and 
formula,  may  be  obtained  of  all  dealers  in  chemical  apparatus. 

Most  of  the  reagents  needed  for  ordinary  chemical  experiments  are  ex- 
ceedingly cheap,  and  may  be  procured  of  any  druggist. 

The  teacher  would,  however,  do  well  to  bear  in  mind,  that  if  his  resources 
in  apparatus  and  chemical  reagents  are  limited,  he  can  supply  himself,  almost 


504  APPENDIX. 

without  cost  and  with  but  little  trouble,  with  abundant  materials  for  render- 
ing his  instructions  both  interesting  and  practical  Thus,  he  has  in  the  com- 
mon varieties  of  coal,  gas-carbon,  plumbago  (black-lead),  coal-tar  and  coal- 
oils,  all  readily  accessible — the  best  materials  for  illustrating  the  study  of 
carbon ;  and  in  wood-ashes,  common  potash,  carbonate  of  soda,  Jime,  mar- 
ble, spar,  oyster-shells,  gypsum,  chalk,  Epsom  salts,  common  salt,  and  alum, 
the  best  illustrations  of  the  alkalies,  the  alkaline  earths,  and  their  compounds. 
In  like  manner,  specimens  of  most  of  the  ores,  the  common  metals,  and  their 
oxyds,  the  products  of  the  smelting  furnace,  the  glass-house,  and  the  pottery, 
with  a  great  variety  of  organic  compounds,  may  be  easily  collected  ;  and  it 
is  by  such  simple  and  common  objects  that  the  applications  of  chemistry  to 
the  wants  and  employment  of  every-day  life  are  made  most  familiar. 

The  operator  will  also  find  it  an  advantage,  in  preparing  and  arranging 
apparatus,  to  have  some  work  on  chemical  manipulations  for  consultation ; 
such  as  Morffit's,  Noad's,  or  Williams'  Chemical  Manipulations,  or  Bowman's 
Practical  Chemistry. 


THE  present  work  constitutes  the  third  of  a  Series  of  Educational  Text- 
books on  Scientific  Subjects,  arranged  upon  the  same  general  plan  by  the 
same  author — the  two  others  being  "  Wells'  Natural  Philosophy,"  and 
"  Wells'  Science  of  Common  Things." 

It  has  been  the  aim  of  the  author  to  render  these  works,  in  the  highest 
sense  of  the  term,  practical,  and  at  the  same  time  interesting  to  the  student. 
Advantage  has  also  been  taken  of  the  very  latest  results  of  scientific  discovery 
and  research. 


INDEX. 


Acid,  tartaric, 
uric,  497 


ACETYLE,  444 

Acetates,  44T 
Acid,  acetic,  445 

antimonic,  381 

arsenic,  382 

arsenious,  381 

benzoic,  473 

fooracic,  27T 

butyric,  429 

carbonic,  290 

chloric,  247 

chromic,  363 

citric,  452 

crenic,  425 

cyanic,  293 

ferric,  361 

fluosilicic,  280 

formic,  447 

fulminic,  299 

gallic,  454 

humic,  425 

hydrochloric,  242 

hydrocyanic,  298 

hydrofluoric,  257 

hydrofluosilicic,  281 

hydrosulphuric,  266 

hypochloric,  247 
hypochlorous,  245 
hyponitric,  234 
hyposulphurous,  265 
lactic,  429 
mallic,  452 
manganic,  363 
margaric,  467-469 
muriatic,  242 
nitric,  228 
nitro-muriatic,  245 
nitrous,  234 
oleic,  467-453 
oxalic,  451 
pectic,  416 
phosphoric,  274 
phosphorous,  275 
prussic,  293 
pyroligneous,  410 
silicic,  279 
stearic,  467-469 
succinic,  473 
snlphindigotic,  460 
sulphuric,  262 
sulphurous,  260 
tannic,  452 


452 


valerianic,  449 
Acids,  classification  of,  ITS 
defined,  174 
vegetable,  450 
Acidification,  theory  of,  445 
Aconite,  457 
Acroleine,  470 
Actinism,  126 
Adhesion,  14 

and  chemical  action,  32 
force  of,  33 

influence  of  on  boiling  point,  97 
Adipocere,  470 
Aeriform  bodies,  18 
Affinity,  characters  of,  159 
defined,  16 

degrees  of,  how  manifested,  160 
illustrations  of,  16 
measure  of  the  force  of,  159 
Air,  analysis  of,  227 
.     composition  of,  224 

does  not  exist  without  vapor,  92 
how  he*ted,  72 
in  water,  216 

influence  of  on  boiling  point,  9T 
organic  bodies  in,  226 
Alabaster,  348 
Albumen,  421 

animal,  482 
Albuminous  substances,  423 

nutritive  value  of, 

424 

Alchemists,  views  of,  157 
Alcohol,  433 

absolute,  439 
amylic,  448 
methylic,  447 
sources  of,  443 
wine,  439 

Alcoholometer,  28,  440 
Aldehyde,  445 
Alkalies,  defined,  174 

general  properties  of,  842 
metals  of,  327 
organic,  455 
Alkalimetry,  338 

Alkaline  earths,  properties  of,  330 
Allotropism,  183,  196 
Alloys,  what  are,  326 
Altitudes,  how  measured  by  boiling  point, 

Alum,  351 


506 


INDEX. 


Alum  baskets,  "how  produced,  46 

relations  to  heat,  74 
Alumina,  351 

silicate  of,  353 
Aluminum,  351 
Amalgams  denned,  326 
Amalgamation,  388 
Amber,  472 
Amethyst,  279 
Ambrotypes,  400 
Ammonia,  340 

carbonate  of,  340 
in  air,  225 
Ammonium,  339 

chloride  of,  340 
sulphide  of,  342 
Ammoniac,  Sal,  340 
Amorphous  bodies,  what  are?  44 
Amyle,  447 

Analysis,  proximate,  405 
Anhydrous,  meaning  of,  218 
Animal  nutrition,  485 

organization,  482 
Anode  and  cathode,  141 
Antimony,  380 

wine  of,  381 
Aqua  ammonia,  342 

regia,  245 
Arabine,  416 
Arbor  saturni,  160 
Ardent  spirits,  438 
Argals,  452 
Argand  burners,  321 
Aridium,  167 
Arsenic,  381 

tests  for,  383 
Arsenious  acid,  381 
Ashes  of  plants,  478 
Asphaltum,  412 
Aspirator,  construction  of,  227 
Assaying,  394 

Athermanous  substances,  74 
Atmosphere,  history  of,  223 

pressure  of,  95,  96 
Atom,  chemical  meaning  of,  172 
Atoms,  estimated  size  of,  173 

what  are,  13 
Atomic  theory,  169 

weights,  table  of,  167 
Axes  of  crystals,  52 
Azote,  220 


B 

Balance,  construction  of,  26 

use  of,  23 
Balsams,  473 
Barium,  343 


Barometer  guage,  108 
Bases  denned,  174 


organic,  456 
Basorine,  416 
Battery,  galvanic,  142 

Bunsen's,  145 

Daniel's,  145 

Grove's,  145 

Smee's,  143 

sulphate  of  copper,  144 

trough,  143 
,  471 


Beaumfe,  registration  of,  28 
Beer,  434 

lager,  436 
Bees-wax,  471 
Benzoine,  473 
Benzole,  411 
Bismuth,  380 
Bitumen,  412 
Black,  Joseph,  223 
Bleaching,  history  of,  249 
theory  of,  239 
powder,  246 

Blood,  constitution  of,  490 
Blow-pipe,  322 

oxyhydrogen,  207 
Blue-pill,  356 
Bodies,  compound,  10 
Boilers,  incrustations  in,  cause  of,  215 

steam,  construction  of,  67 
Boiling,  influence  of  atmosphere  on,  95 
point,  91 

influence  of  adhesion  on,  97 
air  on  water,  97 
Bombs,  asphyxiating,  450 
Bones,  composition  of,  487 
Bouquet  of  wines,  438 
Boracic  acid,  277 
Borax,  278 
Boron,  276 

Brain  and  nerves,  485 
Brass,  379 
Brandy,  439 
Bread,  440 

making,  441 

stale,  442 

toasted,  442 

Brewing,  process  of,  435, 436 
Bricks,  composition  of,  353 
British  gum,  416 
Britannia  metal,  377 
Brimstone,  258 
Bromine,  255 
Bronze,  379 
Brucia,  456 
Bullion,  what  is,  394 
Burning  fluid,  463 
Butter,  489 
Butyric  acid,  429 


Cadmium,  372 
Calcium,  344 

chloride  of,  349 
Calico-printing,  459 
Calomel,  386 
Caloric  denned,  56 
Calorimetry,  77 
Camphene,  463 
Camphor,  artificial,  464 
common,  464 
Candle,  chemistry  of,  317,  318 

combustion  of,  318 
Candles,  adamantine,  469 
Capillary  attraction,  14 

illustrations  of,  15, 16 
Caoutchouc,  474 
Caramel,  419 
Carbon,  282 

a  deodorizer,  288 


INDEX. 


507 


Carbon,  bi-sulphide  of,  296 
Carbonates,  295 
Carbonic  acid,  290 

solidification  of,  293 
solvent  properties  of,  292 
Carbonic  oxyd,  295 
Carburetted  hydrogen  (ligbt),  300 

(heavy),  301 
Cartilage,  484 
Case-hardening,  366 
Caseine,  422 
Cassias,  purple  of,  393 
Catalysis,  161 
Celestine,  344 
Cell  life,  407 
Cells,  formation  of,  406 

size  of,  406 
Cellular  tissue,  407 
Cellulose,  407 
Cementation  (of  steel),  367 
Cements,  345 

and  mortars,    properties  of,  on 
what  depend,  32 

hydraulic,  346 
Cerates,  471 
Charcoal,  287 

adhesive  action  of,  33 
Cheese,  composition  of,  489 
Chemical  action  a  source  of  heat,  62 

what  is,  21 
Chemistry  defined,  21 

inorganic,  156 
Chlorate  of  potash,  186 
Chlorates,  properties  of,  247 
Chloric  acid,  247 
ether,  448 
Chlorimetry,  246 
Chlorine,  235 

history   and    preparation.    235, 
236 

and  hydrogen,  242 

compounds  of,  241 

disinfecting  action  of,  240 

liquid,  237 

peroxyd  of,  247 

relations  to  combustion,  237, 233 

solution,  237 
Chloroform,  448 
Chlorophyle,  460 
Chrome  yellow,  369 
Chromium,  363 
Chyle,  493 
Chyme,  493 
Cinchonine,  456 
Cinnabar,  385 

Circuit,  compound  galvanic,  148 
Citric  acid,  452 
Clay,  353 
Cleavage,  55 
Coal,  anthracite,  286 
bituminous,  287 
mineral,  286 
origin  of,  286 


how  measured,  306 

purified,  304,  305 
Cobalt,  370 
Cochineal,  459 
Cognac,  oil  of,  449 
Cohesion,  14 

and  chemical  action,  29 


Coin,  standard  silver  and  gold,  391 

Coke,  287 

Cold,  greatest  artificial,  60 

how  obtained,  103 
what  is,  57 
Collodion,  408 

process,  in  photography,  400 
Colophony,  471 

Coloring  principles,  organic,  45T 
Colors,  "  fast,"  what  are,  458 

of  the  solar  spectrum,  124 
substantive  and  adjective,  458 
Columbium,  380 

Combination,  chemical,  cause  of,  158 
Combustibles,  what  are,  312 
Combustion,  189,  307,  312 

and  explosion,  313 
light  of,  315 
products  of,  314 
spontaneous,  189 
Compound  Radicals,  404 
Compounds,  chemical,  158 

nomenclature    of, 

176 

Compression  a  source  of  heat,  62 
Concrete,  346 
Condensation  defined,  89 
Conduction  of  heat,  63 

illustrations  of,  63,  64 
Contagion,  431 
Convection,  68 

Cooking,  adaptation  of  water  for,  216 
Copper,  377 

acetate  cf,  379 
alloys  of,  379 
nitrate  of,  379 
oxyds  of,  378 
sulphate  of,  378 

prevention  from  corrosion,  by  sea- 
water,  155 
Copal,  472 
Copperas,  362 
Cordials,  465 
Corrosive  sublimate,  386 
Cotton  fibers,  407 
Cream  of  tartar,  452 
Creosote,  410 
Crocus,  361 
Crops,  rotation  of,  479 
Crystal,  rock,  279 
Crystals,  axes  of,  63 

cleavage  of,  55 

formation  of  in  solid  bodies,  50 
native,  50 

primary  forms  of,  52 
properties  of,  44 
secondary  forms  of,  52 
what  are,  44 
Crystallization,  44 

circumstances  which  influ- 
ence, 45,  46,  47 
purification   by  means  of, 

theory  of,  52 
water  of,  49 
Crystallography,  52 
Cryophorus,  the,  103 
Capillation,  389 

Current,  voltaic,  what  determines  the  di- 
rection of,  140 
Cyanogen,  296 


508 


INDEX. 


Daguerreotypes,  how  taken  in  the  dark,  129 

Daguerreotype  process,  398 

Dalton,  Dr.,  originates  the  atomic  theory, 

169 

Decay,  424 
Decrepitation,  50 
Deliquescence,  49 
Dew,  formation  of,  72 

never  falls,  73 

point,  what  is  the,  73 
Dextrine,  414 
Diamond,  282 
Diamonds,  artificial  formation  of,  284 

form  and  weight  of,  283 
Diastase,  415 

Diathermanous  bodies,  74 
Diffusion  of  gases,  39 
Digester,  Marcet's,  106 
Digestion,  492 
Dimorphism,  54 
Disease,  occasion  of,  433 
Distillation,  99 
Dobereiuer's  lamp,  206 
Donarium,  167 
Drummond  light,  207 
Drying  and  distillation,  100 
Dye-stuff:!,  459 


Earths,  alkaline,  343 

metals  of,  350 
Earthenware,  358 
Ebullition,  conditions  of,  94 

defined,  91 
Eraorescence,  49 
Elasticity,  17 
Electricity  a  source  of  heat,  62 

and  chemical  action,  131 
conductors    and  non-conductors 

of,  133 

fundamental  law  of,  132 
nature  of,  130 

ordinary    and  galvanic,  charac- 
teristics of,  146 
positive  and  negative,  132 
quantity  and  intensity  of,  146 
two  conditions  of,  131 
velocity  of,  134 
voltaic,  134 

Electrolysis  and  electrolytes,  150 
Electro-chemical  decomposition,  148 

theory  of, 

148 

metallurgy,  152 
plating  and  gilding,  153 
Electrodes,  explanation  of,  148 
Element,  chemical,  156 
Elements,  classification  of,  157 

electro-chemical,  order  of,  151 

positive  and  negative,  137 
metallic,  324 
natural  condition  of,  157 
nomenclature  of,  176 
number  of,  9 
table  of,  167 

Emery,  composition  of,  851 
Enamel,  357 


Endosmosis  defined,  86 

illustrations  of,  37 
Endosmotic  action,  influence  of,  38 

force,  38 

English  system  of  weights,  24 
Epsom  salts,  350 
Eremacausis,  425 

Equivalent  proportions,  law  of,  164 
Equivalents,    cliemical,    practical    illustra- 
tions of  the  use  of,  168 
scale  of,  166 
Essences,  461 
Essential  oils,  461 
Ether,  443 

a  form  of  matter,  19 
chloric,  448 
nitrous,  444 
cenanthic,  438 
sulphuric,  443 
varieties  of,  444 
Ethyle,  443 
Eudiometer,  209 
Eupion,  410 

Evaporation,  conditions  of,  91 
defined,  91 
freezing  by,  103 
Expansion  by  heat,  force  of,  79 

theory  of,  77 
Extracts,  fruit,  449 


Fallowing,  480 
Fats,  466 
Fermentation,  427 

acetous,  428 
alcoholic,  428 
viscous,  429 
Fibrine,  483 
Figures,  sensitive,  93 
Filters,  formation  of,  36 
Filtrate,  what  is  a,  30 
Filtration,  cause  of,  35 
Fire,  theory  of  the  ancients  concerning,  807 
annihilators,  2i)l 
damp,  300 
Fixed  oils,  465 
Flax  fibers,  407 
Flame,  59 

blow-pipe,  323 
oxydizing  and  reducing,  323 
structure  of,  318 

Flannels,  why  used  as  protection  against  ex- 
treme temperatures,  66 
Flint,  what  is,  279 
Fluidity  an  effect  of  heat,  87 
Fluorine,  256 
Fluor-spar,  256 
Flux,  definition  of,  278 
Food,  nature  and  functions  of,  498 
Force  converted  into  heat,  61 
definition  of,  12 
indestructible,  19,  20 
varieties,  13 

Forces,  classification  of,  20 
molecular,  13 
natural,  12 

Forests,  influence  of  on  evaporation,  92 
Formic  acid,  447 
Formyle,  448 


INDEX. 


509 


Fowler's  solution,  382 
Freezing  mixtures,  102, 103 
French  system  of  weights,  24 
Friction,  cause  of,  32 

heat  produced  by,  61 
Frost,  73 
Fuel,  economy  of,  67 

how  saved  in  culinary  operations,  101 
Fuller's  earth,  354 
Furnace,  reverberatory,  33T 
Fusel  oil,  448 


Galena,  373 
Gallic  acid,  454 
Galls,  nut,  452 
Galvanic  circuit,  139 

theory  of,  139 
current,  resistances  to,  145 
Galvanism,  134 

how  discovered,  135 
Garanctne,  459 
Garlic,  artificial  oil  of,  450 
Gas  carbon,  286 

how  differs  from  a  vapor,  89 
illuminating,  302 
"  laughing,"  232 
meter,  construction  of,  306 
origin  of  the  term,  223 
Gases,  absorption  of  by  water,  112 
conduction  of  heat  in,  65 
diffusion  of,  39 
endosmotic  action  of,  39 
expansion  of  by  heat,  81 
how  heated,  69 
liquefaction  of,  111 
management  of,  196 
what  are,  18 
Gasometers,  198 
Gauge,  steam,  108 
Gelatine,  484 

Germination,  conditions  of,  434 
Gin,  439 

Glass  and  pottery,  355 
colored,  357 
crown,  355 
Hint,  356 
soluble,  280 
Glauber  salts,  336 
Glow-worms,  114 
Glucose,  419 
Glue,  484 
Gluteji,  422 
Glycerine,  467,  470 
Glycocoll,  485 
Gold,  392 

compounds  of,  393 
fine,  394 
fulminating,  393 
leaf,  394 

Grain  weight,  how  originated,  24 
Gramme,  value  of,  25 
Graphite,  285 
Gravitation,  12 

Gravity  and  chemical  phenomena,  22 
Guano,  480 
Gum,  416 

Arabic,  416 
Senegal,  416 


Gum  tragacanth,  416 

guiacum,  472 

resins,  473 
Gums,  elastic,  474 
Gun-cotton,  407 

powder,  332 

expansive  force  of,  332 
how  manufactured,  332 
Gutta-percha,  475 
Gypsum,  348 


H 


Hair,  composition  of,  486 

dyes,  454 
Haloid  salts,  179 
Hardness,  how  measured,  81 

scale  of,  31 
Hartshorn,  340 

Hayes,  Dr.,  on  air  in  sea-water,  21T 
Heat,  absorption  of,  72 

amount  transmitted  to  the  earth  by 

the  sun,  70 
analysis  of,  127 
and  chemical  action,  56 
and  cold,  extremes  of,  produce  similar 

sensations,  57 
apparent  effects  of,  7T 
capacity  for,  76 
communication  of,  63 
diffusion  of,  57 

disappearance  of  in  liquefaction,  100 
vaporization,  101 

distinguishing  characteristics  of,  56 
effects  produced  by  the  absorption  of 

102 

evolved  by  combustion,  313 
imponderable,  57 
latent,  56, 150 

how  converted  into  sensible, 

114 

measurement,  theory  of,  82 
produced  by  chemical  action,  62 
radiant,  disposition  of,  71 
ratio  between  sensible  and  latent,  110 
reflection  of,  71 
refraction  of,  127,  128 
sources  of,  60 
specific,  75 

standard  for  comparing,  76 
variations  of,  76 
of  atoms,  172 
theory  of,  58 

mechanical,  58 
vibratory,  68 
transmission  of,  T4 
two  conditions  of,  56 
unit  of,  61 

universal  influence  of,  75 
Hematite,  361 
Horny  matter,  486 
Humus,  425 

Hydrate,  what  is  an,  214 
Hydrochloric  acid,  242 
Hydrofluoric  acid,  257 
Hydrogen,  199 

chemical  characteristics  of,  208 
combustion  of,  203 
explosive  compounds  of,  204 
peroxyd  of,  218 . 


510 


INDEX. 


Hydrogen,  phosphuretted,  275 
seleniuretted,  268 
sulphuretted,  266 
Hydrometer,  28 
Hydrosulphuric  acid,  266 

practical  value  of,  29 
Hygrometer,  Daniel's,  94 

hair,  93 
Hygrometers,  principle  nnd  construction  of, 

Hypochlorous  acid,  245 
Hyposulphites,  266 


Ice,  heat  required  to  melt,  101 

influence  of  wind  on  the  formation  of, 

of  salt-water,  why  fresh,  43 

cream,  how  frozen,  103 
Iceland  spar,  properties  of,  119 
Ignis  fatuus,  276 
Illumination,  materials  for,  81T 
Ilmenium,  380 
Incandescence,  59 
Incense,  473 
India-rubber,  474 
Indigo,  459 
Inertia  defined,  11 
Ink,  blue,  298 

printer's,  466 

why  does  not  spread  on  sized  paper  36 

spots,  removal  of,  451 
Inks,  composition  of,  453 

sympathetic,  370 
Insulation,  133 
Iodine,  253 

distinctive  test  for,  256 
Iridium,  396 
Iron,  360 

cast,  362 

galvanized,  371, 156 

in  the  blood,  491 

malleable,  364,  368 

ores  of,  361 

oxyds  of,  360 

pyrites,  362 

specular,  361 

Bulphuret,  362 

tenacity  of,  325 

wrought,  364 

why  adapted  for  castings,  49 
Isinglass,  484 
Isomerism,  182 

two  conditions  of,  182 
Isomorphism,  54 

examples  of,  852 


Jelly,  calves'  foot,  484 
Joule's  experiments  on  heat,  61 


Kakodyle,  450 
Kyanizing,  38T 


Lac,  472 

Lacteals,  491 

Lactic  acid,  429 

Lactine,  420 

Lager  beer,  436 

Lamp,  Berzelius'  spirit,  322 

Dobereiner's,  206 

safety,  320 

vTic,ks'nwhy  nofc  oyerflow,  36 
Lamp-black,  288 
Lamps,  Argand,  321 
Lard,  composition  of,  470 

use  of  steam  in  manufacturing,  110 
Laudanum,  456 
Lavoisier,  310,  311 
Lead,  372 

action  of  on  water,  373 

alloys  of,  375 

carbonate  of,  374 

chromate  of,  369 

sulphate  of,  375 

white,  374 

Lead  pencils,  how  made,  286 
Lead  tree,  160 
Leather,  453 

smell  of,  when  burned,  cause  of, 

Lettuce,  active  principle  of,  456 

Light,  action  of  on  chlorine  and  hydroeen 

238 
matter,  116 

and  heat,  relations  of,  59, 128 

artificial,  requisites  for  the  produc- 
tion of,  320 

corpuscular  theory  of,  113 

degradation  of,  129 

decomposition  of  124 

divergence  of,  116 

Drummond,  207 

electric,  114 

influence  of  on  vegetation,  130 

in  its  chemical  relations,  112 

law  of  diminution  of,  116 

magnetization  of,  124 

most  intense  artificial,  114 

nature  of,  112 

polarization  of,  120 

how  explained,  121 

polarized,  beautiful  phenomena  of, 

how  discovered,  122 
practical  applications  of, 

properties  of,  121 
properties  of,  115 
propagation  of,  115 
reflection  of,  117 
refraction  of,  118 
solar,  calorific  and  chemical  elements 

of,  126 
three  principles  contained  in, 

sources  of,  113 

velocity  of,  116 

undulatory  theory  of,  113 
Lignine,  409 
Lime,  344 

carbonate  of,  346 

caustic,  344 


INDEX. 


511 


Lime,  chloride  of,  246 
gas,  349 

hyposulphite  of,  349 
slacked,  345 
sulphate  of,  348 
superphosphate  of,  2TO 
Linseed  oil,  46l> 
Liquefaction  defined,  89 
Liquids,  cohesion  of,  how  shown,  30 
conduction  of  heat  in,  65 
expansion  of,  by  heat,  80 
how  cooled,  81 
limpid,  30 
temperature  of  in  the  spheroidal 

state,  98 

vapor  produced  by  different,  110 
viscous,  30 
what  are,  18 
Liquors,  artificial,  449 
Litharge,  374 
Lithium,  339 
Litmus,  175,  460 
Loam,  354 

Locomotive  boilers,  construction  of,  6T 
Luminosity  defined,  117 
Lunar  caustic,  390 
Lungs,  structure  and  use  of,  494 


M 


Madder,  459 
Magnesia,  350 

carbonate  of,  350 
sulphate  of,  350 
Magnesium,  349 
Malleable  iron  castings,  365 
Malic  acid,  452 
Malt,  435 
Manganese,  367 
Manures,  480 

animal,  480 
mineral,  481 
vegetable,  481 
Margarine,  466 
Marl,  354 
Marsh -gas,  300 
Mastic,  472 
Matches,  272 
Matter  defined,  9 

divisibility  of,  10 
ethereal  condition  of,  19 
indestructible,  19 
properties  of,  21 
three  forms  of,  17 
Meat,  diseased,  433 
Meats,  method  of  preserving,  439 
Mechanical  action  a  source  of  heat,  61 
Mercaptans,  449 
Mercury,  385 

alloys  of,  387 
chlorides  of,  386 
nitrates  of,  387 
sulphide  of,  387 
fulminating,  300 
Metal,  fusible,  326 
Metalloids,  characteristics  of,  184 

enumeration  of,  184 
Metals,  action  of  nitric  acid  upon,  231 
classification  of,  327 
good  conductors  of  heat,  64 


Metals,  noble,  385 

of  the  alkalies,  327 

oxydatipn  of,  188 

properties  of,  325 

protection  from   corrosion  by  gal- 
vanic agency,  154 

transmutation  of,  modern  views  of, 
157 

strength  of,  how  affected  by  vibra- 
tions, 51 

Meteors,  composition  of,  185 
Meter,  gas,  construction  of,  306 
Meter,  what  is  a,  25 
Methyle,  436 
Miasm,  431 
Mildew,  432 
Milk,  488 

swill,  439 

Mines,  extinguishment  of  fires  in,  291 
Minium,  374 

Moistening  a  source  of  heat,  63 
Molasses,  418 
Molecules  defined,  10 
Molybdenum,  380 
Morphia,  455 
Mortars,  345 
Mother  liquor,  48 
Mucilage,  416 
Muntz  metal,  379 
Muriates,  242 
Music,  how  connected  with  the  composition 

of  the  atmosphere,  226 
Musical  tones  of  burning  hydrogen,  206 


Naphtha,  412 
Naphtaline,  411 
Nascent  state,  162 
Natural  philosophy,  20 
Neutral  bodies,  175 
Nickel,  370 
Niobium,  380 
Niter,  331 

sweet  spirits  of,  444 
Nitrates,  231 
Nitric  acid,  chemical  action  of,  230 

history,  properties,  and  prepa- 
ration, 228,  229 
Nitrogen  and  oxygen,  compounds  of,  227 

chloride  of,  248 

deutoxyd  of,  233 

history  of,  220 

instability  of,  in  composition,  221 

iodide  of,  221 

origin  of,  in  plants,  220 

preparation  and  properties  of,  228 

protoxyd  of,  231 

use  of,  in  the  atmosphere,  225 
Nitro-benzole,  411 

Nomenclature,  chemical,  origin  of,  176 
Nordhausen  sulphuric  acid,  264 
Norium,  167 
Nutrition,  492 
Nux  vomica,  456 


O 


Ocean  currents,  influence  and  cause  of,  69 
Ochres,  354 


512 


INDEX. 


Odors,  classification  of,  465 
Oil,  "  coup,"  411 
fusel,  448 
linseed,  466 
pine,  472 
Seneca,  412 
Oils,  drying,  466 

empyreumatic,  465 
fixed, 466 
mineral,  412 
unctuous,  466 
volatile,  461 
defiant  gas,  301 
Oleine,  466 
Opium,  456 
Organic  chemistry,  401 

bodies,  nature  of,  401 
substances,  origin  of,  403 
structure,  405 
Osmium,  396 
Oxalates,  451 
Oxalic  acid,  451 
Oxyd  defined,  1T6 
Oxygen,  184 

active  and  passive  conditions  of. 
'       193 

and  respiration,  191 
daily  consumption  of,  196 
in  combination,  192 
magnetism  of,  192 
Ozone,  193 

physiological  influence  of,  196 


Palladium,  396 

Palm  oil,  4T1 

Paper,  408 

touch-,  331 

Paradox,  culinary,  96 

Parafine,  411 

Parchment,  artificial,  408 

Parian,  359 

Pearlash,  330 

Peat,  426 

Pectine,  416 

Pelopium,  380 

Pepsine,  493 

Percussion  a  source  of  heat,  62 
caps,  300 

Perspiration  and  evaporation,  influence  of, 
on  animal  heat,  104 

Petrifactions,  294 

Petrolium,  412 

Pewter,  377 

Pyrometer,  Daniel's,  88 

Pyrometers,  construction  of,  87,  88 

Phlogistic  theory,  307 

Phlogiston,  307 

Phosphorescence,  114 

Phosphoric  acid,  274 

glacial,  274 

Phosphorus,  269 

allotropic,  or  amorphous,  272 
combustion  of,  in  oxygen,  191 
influence  of,  upon  iron,  365 

Phosphuretted  hydrogen,  275 

Photographs  in  colors,  409 

on  what  principle  formed,  129 
paper,  399 


Photography,  397 
Physics  defined,  20 
Physiology,  what  is,  20 
Pig-iron,  364 
Pile,  voltaic,  136 

Zamboni's  dry,  138 
Pitch,  410 
Planetary  spaces,  estimated  temperature  of. 

60 

Plants,  action  of,  on  the  atmosphere,  478 
contain  nitrogen,  220 
contents  of  the  cells  of,  412 
essential  immediate  principles  of, 

405 

evolve  oxygen,  168 
mineral  constituents  of,  475 
nutrition  and  growth  of,  475 
Plaster  of  Paris,  348 

a  non-conductor  of  heat,  67 
Plating,  391 
Platinum,  395 

adhesive  action  of,  34 
sponge,  effects  of,  205 
Plumbago,  286 
Poison,  "  Woorara,"  456 
Poisons,  4;iO 

Polarization  of  light,  120 
Poles  of  a  galvanic-battery,  141 
Pomatums,  462 
Porcelain,  359 
Pores,  11 

of  leaves,  476 
Porosity,  what  is,  11 
Potassa  (potash),  329 

carbonate  of,  330 
chlorate  of,  186,  247 
caustic,  329 
chromate  of,  369 
iodide  (hydriodate)of,255 
nitrate  of,  331 
prussiate  of,  297 
sulphate  of,  351 
Potassium,  827 

cyanide  of,  298 
ferrocyanide  of,  297 
ferridcyanide  of,  298 
Precipitation  defined,  42 

how  effected,  42,  43 
Presence,  "  action  of,"  162 
Proof  spirit,  439 
Proteine,  422 
Proximate  principles,  405 
Prussian  blue,  296,  297 
Prussic  acid,  298 
Puddling,  364 
Pulse-glass,  96 

Pulverization,  effect  of,  on  adhesion,  33 
Purification  by  crystallization,  47 
Putrefaction,  425 
Putty,  466 
Pyrites,  iron,  362 
Pyroligneous  acid,  410 
Pyroxyline,  407 
Pytaline,  492 


Quartation,  a 
Quinine,  456 


Q 

lying  by,  394 


INDEX. 


613 


Radiation,  69 

influence  of  color  on,  70 
influence  of  surface  on,  70 

Radiators,  good  and  bad,  70 

Radical,  chemical,  179 

Radicals,  compound,  296 

Reactions  and  reagents,  181 

Rectification,  99 

Red  colors,  459 

precipitate,  386 

Refraction,  double,  119 
of  light,  119 

Refrigerators,  principle  of  construction  of, 
66,67 

Repulsion,  16 

illustrations  of  the  force  of,  17 

Resins,  471 

Respiration,  495-496 


Rhodium,  396 
River-water,  purity  of,  213 
Rochelle  salts,  452 
Roman  cement,  346 
Rosin,  471 
Rouge,  361 

Rubber,  vulcanized,  474 
Ruby,  composition  of,  351 
Rupert1  s  drops,  357 
Russia  sheet-iron,  365 
Ruthenium,  396 


S 


Safety-lamp,  Davy's,  320 
Saline  springs,  213 
Saliva,  492 
Sal  ammoniac,  340 

soda,  336 
Saleratus,  331 
Salinometer  explained,  95 
Salted  meats,  use  of,  as  food,  500 
Saltpeter,  331 

not  explosive,  331 
Salt  an  antiseptic,  500 
common,  334 
rock,  334 

relations  to  heat,  74 
Salts,  classification  of,  178 
defined,  174 
haloid,  179 
of  sorrel,  451 
Sandstone,  what  is,  279 
Sap  of  plants,  what  is,  412 
Saturation  of  liquids,  41 
Sausages,  poisonous,  432 
Bcagliola,  349 

Sea,  "  phosphorescence"  of,  115 
transparency  of,  212 
waters,  composition  of,  214 
Sealing-wax,  472 
Selenium,  268 
Serpentine,  349 

Sheet-iron,  Russia,  how  made,  365 
Shellac,  472 
Shot,  376 
Silica,  279 
Silicon,  or  Silicium,  279 


Silicon,  fluoride  of,  281 
Silver,  388 

chloride  of,  391 
fulminate  of,  300 
nitrate  of,  390 
oxyds  of,  389 
Silvering,  391,  392 
Sizing,  484 

Skin,  composition  of,  485 
Slag,  363 
Smalt,  370 

Smelting  of  iron,  363 
Snow,  crystals  of,  45 

line  of  perpetual,  76 
protecting  influence  of,  66 
Soaps,  467 
Soapstone,  349 
Soda-ash,  336 
Soda,  biborate,  278 

carbonate  of,  336 
caustic,  334 
nitrate  of,  338 
sulphate  of,  336 
powders,  452 
water,  what  is,  292 
Sodium,  333 

chloride  of,  334 
Soils,  origin  of,  478 
Solids,  conduction  of  heat  in,  64 
expansion  of,  by  heat,  78 

in  crystallizing,  48 
variation  of  cohesion  in,  31 
what  are,  17 
Solution  and  chemical  combination,  43 

defined,  41 
Soot,  287 
Soup,  why  retains  heat  longer  than  water, 

68 
Spar,  heavy,  343 

Derbyshire,  256 
Specific,  heat,  172 

gravity,  26 

of  gases,  how  determined, 

29 

of  solids  and  liquids,  27 
Spectrum,  solar,  125 

fixed  lines  in,  125 
Spheroidal  state,  98 
Spirits  of  wine,  439 
Spring,  air  of,  why  chilly,  104 
Springs,  mineral,  213 
saline,  213 
thermal,  213 
Stalactites,  347 
Stalagmites,  34T 
Starch,  413 

Stars,  fixed,  light  of,  125 
Steam,  curious  experiments  on,  109 
expansive  force  of,  106 
high-pressure,  109 
invisible,  90 
latent  heat  of,  101 
pressure  of,  when  formed  in  open 

air,  106 

pressure,  varying  conditions  of,  108 
relation  between  temperature   and 

pressure  of,  107 

rule  governing  the  elasticity  of,  106 
super-heated,  110 
why  adapted  for  cooking,  105 
Stearine,  . 
22* 


514 


INDEX. 


Steel,  365 
Strontium,  344 
Strychnia,  456 
Stucco,  349 
Sublimation,  99 
Substances,  simple,  9 
Substitution,  law  of,  165 
Sugar,  411 

cane,  41T 

grape,  419 

manna,  420 

milk,  420 

refining,  418 

boiling,  97 

of  lead,  447 
Sulphates  defined,  178 
Sulphides  defined,  178 
Sulphites  defined,  178 
Sulphur,  258 

allotropism  of,  259 
flowers  of,  258 
milk  of,  260 
oils  containing,  464 
alcohols,  449 

Sulphuretted  hydrogen,  266 
Sulphuric  acid,  262 
Sulphurous  acid,  260 
Surface  action,  33 
Sun,  character  of  the  light-giving  substance 

of,  122 

the,  a  source  of  heat,  60 
Symbols,  chemical,  179,  180 
Sympathetic  Inks,  370 
Syrup,  "  sugar-house,1'  418 


Talc,  349 

Tallow,  470 

Talbotype,  399 

Tannic  acid,  452 

Tannin,  452 

Tar,  coal,  411 
wood,  410 

Tartar,  crude,  452 
emetic,  381 

Tartaric  acid,  452 

Tellurium,  268 

Temperature  defined,  57 

greatest  natural,  60 

Tension,  electricity,  146 
of  vapors,  106 

Test  papers,  175 
tubes,  185 

Thermometer,  air,  87 

Breguet's,  86 
Centigrade,  84 
differential,  86 
Fahrenheit's,  87 
mercurial,  83 
metallic,  86 
Reaumur's,  84 
self-registering,  85 
spirit,  87 
what  it  informs  us  of,  8 

Tides,  motion  of,  a  source  of  heat,  62 

Tin,  376 

plate,  377 

Tinctures,  wfoat  are,  440 

Titanium,  380 


Trough,  pneumatic,  196 
Tungsten,  380 
Turpentine,  crude,  463 

oil,  or  spirits  of,  464 
Twaddell's  hydrometer,  28 
Type-metal,  376 


Ultramarine,  354 
Uranium,  380 
Urea,  497 
Urine,  what  is,  497 


Vacuo,  boiling  in,  97 

Valerian,  449 

Vanadium,  380 

Vaporization  defined,  89 

Vapors,  comparative  volume  ofi  90 

density  of,  91 

diffusion  of,  40 

elastic  force  of,  105 

expansion  of,  by  heat,  81 

form  at  all  temperatures,  90 

how  heated,  69 

invisible,  90 

when  cease  to  expand,  105 
Varnish,  473 
Vegetable  acids,  450 

extracts,  457 

Vegetation,  influence  of  light  on,  130 
Verdigris,  379,  447 
Vermilion,  387 
Vinegar,  446 

wood,  446 
Vitriol,  blue,  378 

green,  362 

white,  372 
Volatile  bodies,  89 
Volumes,  equivalent,  168 


W 


Washing  fluids,  469 
Water,  action  of,  on  lead,  373 
air  in,  216 

coloration  of  vast  bodies  of,  212 
composition  of,  209 

how  proved,  209 
decomposition  of,  148 

by  heat,  200 

heat  produced  in,  by  friction,  61 
history  of,  210 
how  heated,  68 
of  crystallization,  49 
properties  of,  211 
salt,  freezing  point  of,  81 
solvent  properties  of,  217 
when  attains  its  greatest  density,  81 
when  basic,  218 
when  increases  the  intensity  of  a 

fire,  201 

unequal  expansion  of,  80 
Waters,  comparative  purity  of,  212 
hard  and  soft,  215 
medicated,  462 


INDEX. 


515 


Waters,  relative  fitness  for  use,  214 

spring,  comparative  purity  of,  212 
•Wax,  471 

shoemaker's,  472 


1,13 

compared  with  bulk,  26 
specific,  26 
Weights,  French  and  English,  24,  25 

two  great  systems  of,  23 
Welding,  326 

Wheat,  composition  of,  441 
Wind,  influence  of,  on  evaporation,  92 
Winds,  how  produced,  69 
Wines,  437 
Wood,  carbonization  of,  by  steam,  110 

destructive  distillation  of,  409 
Wool,  structure  of,  486 


Woolens,  why  adapted  for  clothing,  65 

Wort,  435 

Woulfe's  apparatus,  244 


Yeast,  427 

powders,  442 
Yellow  dyes,  460 


Zinc,  371 

sulphate  of,  372 
white,  3T2 
amalgamation  of,  143 


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